KR102378296B1 - Plasma Apparatus - Google Patents

Abstract

The present invention provides a plasma generating device. This plasma device comprises a dielectric discharge tube; a swirl generator that receives a gas supply and provides a swirl flow in the dielectric discharge tube; an induction coil disposed to surround the dielectric discharge tube to generate an induced electric field to generate plasma; and an AC power supply for supplying power to the induction coil. includes

Description

Plasma Apparatus

The present invention relates to a plasma device, and more particularly, to an inductively coupled plasma device that performs discharge at atmospheric pressure or above atmospheric pressure.

Among the gases that make up the atmosphere, the gases that cause the greenhouse effect are called greenhouse gases. Methane (CH4) and carbon dioxide (CO2) are the most important global warming gases and are on the agenda of the global warming problem. The synthesis of syngas (synthesis gas) according to the conversion reaction of CH4 and CO2 (CH4 + CO2 -> 2 H2 + 2 CO) is attracting attention as a major concern. Conversion treatment of methane and carbon dioxide using atmospheric pressure plasma is a very effective method. The atmospheric pressure plasma system has the advantage that it does not require a separate vacuum equipment required for vacuum plasma along with a fast conversion reaction, and is easy to implement.

CH4-CO2 reforming is attracting attention according to the regulatory environment for the continuous reduction of petroleum resources and reduction of greenhouse gases. Plasma technology is considered as one of the most promising methods of CH4-CO2 reforming. Plasma reforming core technology requires high conversion efficiency and high feed-gas flow rate. In order to achieve this, the main factors of electron density, plasma temperature, and reactor structure are emphasized. Considering the current state of plasma CH4-CO2 reforming, it is possible to increase the energy conversion efficiency and treatment capacity by optimizing the reactor structure and plasma type.

With the continuous reduction of petroleum resources and the emphasis on environmental conditions, and with chemical energy transmission, synthesis gas production is focusing on CH4-CO2 reforming (referred to as dry reforming).

CH4 + CO2 ->2 CO + 2H2 ; ΔH = 247 kJ/mol

CH4-CO2 reforming reduces the consumption of methane and makes the use of carbon dioxide more attractive. To produce the same CO, less methane is used compared to steam reforming and partial oxidation, and CO2 is used as the carbon source in the reforming process. Although, CH4-CO reforming maintains the H2/CO ratio at 1/1, the H2/CO ratio can be adjusted by adjusting the CH4/CO2 ratio of the supplied gas.

Referring to Korean patents KR 1255152 and KR 1166444, in an Integrated Gasification Combined Cycle (IGCC), coal is converted into syngas containing hydrogen (H2) and carbon monoxide (CO) as main components, and then this gas is used A method for generating electricity is disclosed. Specifically, in order to produce syngas, a plasma gasifier using a very high frequency has been introduced. However, the very high frequency gasifier has a limitation of the very high frequency power used, and thus it is difficult to enlarge it.

Referring to US Patent No. 7622693, the production of syngas using inductively coupled plasma is disclosed. However, although an inductively coupled plasma apparatus using an induction coil having a single layer structure is disclosed, it is difficult to perform plasma discharge in an induction coil having a single layer structure at atmospheric pressure.

One technical problem to be solved by the present invention is to provide an atmospheric pressure inductively coupled plasma device that can stably discharge atmospheric pressure.

One technical problem to be solved by the present invention is to provide an atmospheric pressure inductively coupled plasma apparatus capable of producing synthesis gas by stably discharging carbon dioxide-methane.

A plasma apparatus according to an embodiment of the present invention includes a dielectric discharge tube; a swirl generator that receives a gas supply and provides a swirl flow in the dielectric discharge tube; an induction coil disposed to surround the dielectric discharge tube to generate an induced electric field to generate plasma; and an AC power supply for supplying power to the induction coil. includes

In one embodiment of the present invention, the plasma is supplied with carbon dioxide and methane to generate a synthesis gas containing hydrogen and carbon monoxide at atmospheric pressure, and the flow rate of the gas may be several tens of liters to several hundreds of liters per minute.

In one embodiment of the present invention, the induction coil may be in the form of a solenoid having a multi-layer structure.

In an embodiment of the present invention, the induction coil includes a lower solenoid coil disposed to surround the dielectric discharge tube; and an upper solenoid coil disposed to surround the lower solenoid coil. The lower solenoid coil and the upper solenoid coil may be connected in series, and the direction of the magnetic field generated by the lower solenoid coil may be the same as the direction of the magnetic field generated by the upper solenoid coil.

In one embodiment of the present invention, the induction coil further comprises an intermediate solenoid coil disposed between the lower solenoid coil and the upper solenoid coil, the lower solenoid coil, the intermediate solenoid coil, and the upper solenoid coil may be connected in series, and directions of magnetic fields generated by the lower solenoid coil, the middle solenoid coil, and the upper solenoid coil may be the same.

In one embodiment of the present invention, the frequency of the AC power supply may be 100 kHz to 4 MHz.

In one embodiment of the present invention, the induction coil includes a plurality of multilayer structure induction coil modules, the multilayer structure induction coil modules are electrically connected to each other in parallel, and the magnetic field generated by the multilayer structure induction coil module is mutually may interfere constructively.

In one embodiment of the present invention, the induction coil may have a solenoid coil structure having a two-layer structure, and the induction coil may have 4 turns in the lower layer and 4 turns in the upper layer.

In an embodiment of the present invention, the swirl generator is disposed at one end of the dielectric discharge tube to seal the dielectric discharge tube, and provides a fluid velocity component in an azimuth direction in a cylindrical coordinate system to pressurize the dielectric discharge tube with a radial radius. Tea can be provided. Plasma generated by the induction coil may suppress contact with the sidewall of the dielectric discharge tube.

In one embodiment of the present invention, the swirl generator is formed to have a tangential component periodically on a circumference of a constant radius along the inner wall of the dielectric discharge tube to provide a swirl flow; and an inner nozzle formed to have a tangential component periodically on a circumference of a constant radius inside the outer nozzle to provide a swirl flow.

In an embodiment of the present invention, a swirl guide disposed between the inner nozzle and the outer nozzle, extending in the longitudinal direction of the dielectric discharge tube, made of a dielectric material, and having a cylindrical shape may further include.

In one embodiment of the present invention, the swirl generating unit provides a flow rate of an azimuth direction component in a cylindrical coordinate system, one end of the dielectric discharge tube is coupled to the outer injector comprising a plurality of outer nozzles; an outer support portion coupled to the outer injector portion to provide an outer buffer space; an outer sealing portion coupled to the outer support portion to seal the outer buffer space; an inner support that is inserted into the outer closure and provides an inner buffer space; It may include an inner injector that provides a flow rate of an azimuth direction component and is inserted into the inner support to seal the inner buffer space and includes a plurality of inner nozzles. The outer nozzle may be connected to the outer buffer space, and the inner nozzle may be connected to the inner buffer space.

In one embodiment of the present invention, the swirl generating unit may further include a central injector that is inserted into the inner injector and discharges gas through a through hole formed in the center without swirl flow.

In one embodiment of the present invention, the outer nozzle may be formed in a helical shape while rotating in an azimuth direction on a circumference of a constant radius while proceeding in the longitudinal direction of the dielectric discharge tube.

In an embodiment of the present invention, the inner nozzle may be formed in a helical shape while rotating in an azimuth direction on a circumference of a constant radius while proceeding in the longitudinal direction of the dielectric discharge tube.

In one embodiment of the present invention, it may further include a swirl guide disposed between the inner nozzle and the outer nozzle and having a dielectric cylindrical shape extending in the longitudinal direction of the dielectric discharge tube. The swirl guide may be disposed to be inserted between the inner support part and the outer support part.

In an embodiment of the present invention, an initial discharge generating unit disposed around the dielectric discharge tube to provide an initial discharge may be further included.

In an embodiment of the present invention, the initial discharge generating unit includes a plurality of initial discharge electrodes disposed along an outer surface of the dielectric discharge tube; and a high voltage power supply for applying a high voltage to the initial discharge electrode.

In one embodiment of the present invention, it is disposed around the induction coil may further include a magnetic flux confinement formed of a magnetic material to confine the magnetic flux generated by the induction coil.

In an embodiment of the present invention, the magnetic flux confinement unit may include a plurality of magnetic blocks that are symmetrically disposed in a plane perpendicular to the central axis of the dielectric discharge tube. The magnetic block may be disposed to surround an outer surface, an upper surface, and a lower surface of the induction coil.

In one embodiment of the present invention, the magnetic flux confinement unit is a magnetic block disposed to surround the induction coil; A heat conduction plate formed of a non-magnetic material disposed to surround the magnetic block so as to be in contact with the magnetic block and transfer heat from the magnetic block; and a cooling pipe fixed to the heat conduction plate to cool the heat conduction plate. The heat conduction plate may include a slit for blocking the flow of the induced current generated by the induction coil.

In an embodiment of the present invention, an auxiliary dielectric tube may be disposed at the center of the dielectric discharge tube.

Inductively coupled plasma apparatus according to an embodiment of the present invention generates a synthesis gas by performing carbon dioxide-methane using a large-capacity gas at atmospheric pressure or above atmospheric pressure.

1 is a conceptual diagram for hydrogen production according to an embodiment of the present invention.
2 is a schematic diagram of a gas cracking system according to an embodiment of the present invention.
3 is a schematic diagram illustrating a plasma apparatus according to an embodiment of the present invention.
4A is a cut-away perspective view illustrating an induction coil having a stacked structure according to an embodiment of the present invention.
Fig. 4b is a cross-sectional view of the induction coil of Fig. 4a;
4C is a circuit diagram illustrating an induction coil of the stacked structure of FIG. 4A.
5A is a cut-away perspective view illustrating an induction coil having a parallel structure according to an embodiment of the present invention.
Fig. 5b is a cross-sectional view of the induction coil of Fig. 5a;
5C is a circuit diagram illustrating an induction coil of the stacked structure of FIG. 5A.
6 is a cut-away perspective view illustrating a swirl providing unit of a plasma apparatus according to an embodiment of the present invention.
7 is a cross-sectional view illustrating a magnetic flux confinement unit of a plasma apparatus according to an embodiment of the present invention.
8 is a perspective view illustrating the magnetic flux confinement unit of FIG. 7 .
9 is a view for explaining a plasma apparatus according to another embodiment of the present invention.
10 is a view showing experimental results of a plasma generating apparatus according to an embodiment of the present invention.
11 is a view showing experimental results of a plasma generating apparatus according to an embodiment of the present invention.

Inductively coupled plasmas are typically formed using a driving frequency of several MHz at a pressure of several hundred milliTorr (mTorr). However, in such an inductively coupled plasma, it is difficult to perform atmospheric pressure discharge due to the small intensity of the induced electric field. Therefore, sufficient strength of the induced electric field is required and a separate means for initial discharge is required.

When RF power is applied to an induction coil surrounding the dielectric tube to perform inductively coupled plasma discharge, the inductively coupled plasma heats the dielectric tube, and the dielectric tube is heated and damaged. Therefore, the high-power inductively coupled plasma has a structural limitation.

A swirl may be provided to minimize heat transfer between the inductively coupled plasma and the dielectric tube and to maintain stability of the plasma. In a cylindrical coordinate system, the orbiting flow may provide angular momentum in an azimuthal direction to a gas or fluid, thereby providing a density distribution along a radial direction. Accordingly, the inductively coupled plasma is locally confined to the central region of the dielectric tube. Accordingly, heat transfer between the inductively coupled plasma and the dielectric tube can be minimized.

[purpose of use]

Such an atmospheric pressure plasma apparatus can be used for various purposes. For example, the atmospheric pressure plasma apparatus can be used for the synthesis of nano-powders, the synthesis of single-walled carbon tubes, the synthesis of fullerenes, and the synthesis of diamond films. It can be used for synthesis, synthesis of optically transparent film, surface treatment, decomposition of gas, gasification of coal, generation of synthesis gas, treatment of harmful gas, reforming of gas, and the like.

According to an embodiment of the present invention, in order to generate a synthesis gas using plasma at atmospheric pressure or a high pressure higher than atmospheric pressure, an inductively coupled plasma is used for plasma reforming. Conventional RF inductively coupled plasma is difficult to discharge at atmospheric pressure. Even in the case of discharge, it is difficult to maintain discharge stability. Accordingly, according to an embodiment of the present invention, an apparatus and method capable of stably performing plasma discharge in a large capacity at atmospheric pressure and a pressure greater than or equal to atmospheric pressure are introduced.

According to an embodiment of the present invention, the plasma apparatus may be an inductively coupled plasma source that maintains a glow discharge at 0.1 atm to 5 atm. In the case of maintaining the plasma, a gas such as Ar, CO2, CH4, NF3, O2, H2 may be used, and tens to hundreds of liters of gas per minute are supplied and exhausted into the plasma source.

According to one embodiment of the present invention, there is provided a plasma apparatus having high plasma impedance and reduced gas flow instability. Plasma devices capable of processing a flow rate of tens to hundreds of liters per minute have a great influence on the stability of the plasma and the gas decomposition performance of the flow dynamics and gas flow pattern. The flow dynamics improve plasma stability and increase plasma and gas interactions.

According to an embodiment of the present invention, in order to improve the efficiency or stability of the conventional inductively coupled plasma, 1) an antenna (coil structure) of a stacked structure to increase the intensity of the induced electric field, 2) for reducing the impedance of the induction coil Parallel structure, 3) magnetic flux confinement means to increase the strength of the induced electric field, 4) a swirl generator that can be easily mounted on a cylindrical discharge tube providing gas swirl flow, 5) a swirl guide to provide a stable flow pattern , 6) an auxiliary dielectric tube structure that provides a gas that performs an endothermic reaction to a plasma generating position to efficiently utilize heat generated in the plasma, 7) an initial discharge means for efficiently generating an initial discharge, 8) provides a swirl flow An auxiliary swirl generator that improves gas-plasma interaction and increases flow stability by providing a gas swirl in the same direction as the swirl generator, 9) AC power supply for improving plasma stability of the induction coil, etc. are applied. Accordingly, a flow rate of several tens to several hundred liters per minute, which the conventional inductively coupled plasma apparatus could not perform, can be stably processed at atmospheric pressure.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed subject matter may be thorough and complete, and that the spirit of the present invention may be sufficiently conveyed to those skilled in the art. In the drawings, components are exaggerated for clarity. Parts indicated with like reference numerals throughout the specification indicate like elements.

1 is a conceptual diagram for hydrogen production according to an embodiment of the present invention.

Referring to FIG. 1 , a hydrogen station 10 is an infrastructure technology for commercialization of fuel cell vehicles and hydrogen internal combustion engines, and is a hydrogen charging station that supplies hydrogen to fuel cells and hydrogen vehicles. A hydrogen station can be divided into a method of producing hydrogen at a factory and transporting it to a vehicle and supplying it to a vehicle, or manufacturing hydrogen locally and supplying hydrogen to a vehicle. Methods for producing hydrogen by on-site method include water electrolysis method and fossil fuel reforming method. The hydrogen station, which produces hydrogen by reforming fossil fuels on-site, measures the carbon monoxide (CO) concentration in the desulfurization process, the hydrogen manufacturing process (reforming) by the reforming reaction of fuel, and the generated excess hydrogen gas (hydrogen rich gas). Hydrogen refining (water gas shift; WGS) process, high-purity hydrogen adsorption (PSA) process, hydrogen storage process that stores hydrogen under pressure, and dispensing process that supplies hydrogen to fuel cell vehicles Consists of. The fuel storage unit 11 that receives and stores methane gas provides methane gas to the desulfurization process unit 12 . The desulfurization process unit 12 provides methane gas to the reformer 13 by removing sulfur. The reformer 13 receives methane and carbon dioxide as a plasma reformer and decomposes through plasma to produce syngas such as carbon monoxide and hydrogen. Since the reforming unit 13 has high thermal energy, the synthesis gas is cooled through the heat exchange unit 14 . The cooled synthesis gas purifies hydrogen through the hydrogen purification unit (WGS, 15), and the purified hydrogen is provided to the hydrogen adsorption unit 16 . The hydrogen adsorption unit 16 separates hydrogen, carbon dioxide, and methane. The separated hydrogen may be used as a fuel in a fuel cell, power generation, and the like.

Fuel reforming technology is largely classified into steam reforming, partial oxidation reforming, auto-thermal reforming, carbon dioxide reforming (CO2 reforming), plasma reforming, and the like.

The plasma reforming process has a fast start-up characteristic due to the heat source generated from its own plasma, the reaction control is easy, and the hydrogen conversion rate is high compared to the energy supply. In addition, it can be applied to various fuel properties. However, it has the disadvantage that it is difficult to control the selectivity of the product and the initial equipment cost is high. According to an embodiment of the present invention, a stable reforming reaction can be maintained at atmospheric pressure or a pressure higher than atmospheric pressure by using an inductively coupled plasma source as the plasma reforming apparatus.

2 is a schematic diagram of a gas cracking system according to an embodiment of the present invention.

Referring to FIG. 2 , the gas cracking system 20 may be used for the production of synthesis gas or various gas cracking. The gas cracking system may be a plasma reformer using carbon dioxide and methane as raw materials. In the case of the synthesis gas production, the source gas may be methane and carbon dioxide.

As an example of the gas cracking system, a gas cracking system using carbon dioxide and methane as raw materials is described.

The gas decomposition system 20 may include a gas supply unit 21 , a gas decomposition inductively coupled plasma device 22 , and an exhaust and gas collection unit 23 . The gas decomposition inductively coupled plasma apparatus 20 may be connected to each other in parallel. Accordingly, it is possible to increase the processing flow rate. The gas decomposition inductively coupled plasma apparatus 20 may operate at atmospheric pressure.

The gas supply unit 21 may supply various fuels to the plasma apparatus. The fuel may be methane and carbon dioxide. The fuel may be biogas or various hydrocarbon gases. The gas supply unit 21 may provide an auxiliary gas such as argon (Ar) for plasma initial discharge or discharge stability.

The exhaust and gas collection unit 23 may collect and process the generated synthesis gas. The exhaust and gas collecting unit 23 may measure the concentration of carbon monoxide and the like, and collect carbon monoxide and hydrogen. The gas decomposition inductively coupled plasma apparatus may be coupled to a heat exchanger that recovers the generated heat. In addition, the exhaust and gas collection unit 23 may be configured to include a hydrogen purification unit and a hydrogen adsorption unit.

3 is a schematic diagram illustrating a plasma apparatus according to an embodiment of the present invention.

Referring to FIG. 3 , the inductively coupled plasma apparatus 100 includes a dielectric discharge tube 110 ; a swirl generator 140 receiving a gas supply and providing a swirl flow in the dielectric discharge tube; an induction coil 120 disposed to surround the dielectric discharge tube 110 to generate an induced electric field to generate plasma; and an AC power supply unit 129 for supplying power to the induction coil. includes The inductively coupled plasma apparatus 100 may generate synthesis gas (carbon monoxide and hydrogen) by decomposing source gases (methane and carbon dioxide) at atmospheric pressure or a pressure higher than atmospheric pressure.

The dielectric discharge tube 110 isolates the discharge region where the discharged plasma is located and the outside. The pressure of the dielectric discharge tube 110 may be substantially atmospheric pressure or a pressure higher than atmospheric pressure. If the decomposed gas leaks to the outside, it can be harmful. Therefore, in the case of generation of harmful gas, the dielectric discharge tube can be sealed. The dielectric discharge tube may be cylindrical. The dielectric discharge tube may preferably have a cylindrical shape. However, since the dielectric discharge tube 110 operates at atmospheric pressure, it may be variously deformed, such as a cylinder, an oval cylinder, or a square cylinder. The material of the dielectric discharge tube 110 may be quartz, ceramic, alumina, or sapphire. It may be preferable that the dielectric discharge tube is made of quartz, which is easy to manufacture and is resistant to thermal shock. The dielectric discharge tube 110 is formed of a non-conductive material to transmit an induced electromotive force.

The atmospheric pressure inductively coupled plasma may be discharged by the induction coil 120 . The internal pressure of the dielectric discharge tube 110 may be preferably in the range of 300 Torr to 1000 Torr. When the pressure of the dielectric discharge tube 110 approaches atmospheric pressure, it is difficult to generate inductively coupled plasma, but the high pressure can handle a large flow rate. On the other hand, when the pressure of the dielectric discharge tube 110 is several torr to 100 torr, the inductively coupled plasma can be easily generated, but the flow rate is significantly reduced and the swirl flow is reduced. That is, the dielectric discharge tube 110 to which a high power of several tens of kWatt or more is applied may be damaged by heat due to an increase in the diffusion coefficient of the gas according to the decrease in pressure.

The diameter of the dielectric discharge tube 110 affects the inductance of the induction coil 120 surrounding the dielectric discharge tube. When the inductance of the induction coil increases, the AC power or RF power cannot efficiently supply power to the load (including the induction coil). Accordingly, the diameter of the dielectric discharge tube 110 may range from several centimeters to several tens of centimeters. Preferably, the outer diameter of the dielectric discharge tube may be on the order of 8 centimeters. The inductance of the induction coil may be in the range of 5 uH to 20 uH.

Conventional solenoid-type induction coils are difficult to generate an induced electric field strong enough to sustain discharge and cause sufficient gas decomposition. The induction electric field is easily generated through the induction coil as the frequency increases, but as the frequency increases, it is difficult to manufacture a power source that generates high power of several tens of kilowatts (kWatt) or more. Typically, in the case of a frequency domain of several hundred kilohertz (kHz) or less, a power source of several tens of kWatt or more may be manufactured. In the case of a frequency range of several MHz or more, it is difficult to manufacture a power source of several tens of kWatt. Therefore, in order to supply power of several tens of kWatt or more, the AC power supply unit 129 may have a frequency of several MHz or less. 100 kHz to 4 MHz of the AC power supply unit 129, preferably 400 kHz. Also, the AC power supply unit 129 may be a variable frequency power supply to improve impedance matching or discharge stability. That is, the frequency of the initial stage of the discharge may be different from the frequency of the state in which the discharge is stably maintained.

The induction coil 120 must induce a strong electric field in order to discharge atmospheric pressure plasma by using a gas such as CO2, CH4, and high energy per unit time must be input to the plasma in order to increase gas reaction efficiency. . To this end, the antenna or induction coil has the following characteristics. A refrigerant such as pressurized air or water may flow inside the induction coil 120 for cooling. Nevertheless, even when a refrigerant flows inside the induction coil, when power of several tens of kWatt or more is supplied, the induction coil may be heated and melted. Accordingly, the induction coil may be formed of a copper material and plated with silver to reduce surface resistance.

[Structure of multi-layer induction coil]

Currently, atmospheric pressure inductively coupled plasma devices apply very-high frequency (VHF) power to induce a high electric field in the discharge space. Typically, atmospheric pressure inductively coupled plasma devices use 27.4 MHz. In the case of this 27.4 MHz frequency, plasma discharge and maintenance are easy, but it is impossible to apply high power to plasma with high efficiency due to technical limitations of RF generator and impedance matching. Therefore, the gas decomposition and the CH4-CO2 plasma reforming reaction cannot be efficiently performed. In particular, the CH4-CO2 plasma reforming reaction requires a thermal plasma. Up to now, an inductively coupled plasma device using a power of several tens of kWatt or more at a low frequency of several MHz or less has not been required. Typically, the atmospheric pressure discharge is easily discharged using a plasma torch. Therefore, there was no need for an inductively coupled discharge for atmospheric pressure discharge. However, in the case of a plasma torch, since the electrode is consumable, replacement and repair occur frequently. In the case of atmospheric pressure ultra-high frequency discharge, although discharge is easy, a magnetron that is mechanically complicated and outputs power of several tens of kWatt or more is not realistically or too expensive. On the other hand, in the inductively coupled plasma, the induced electric field is not normally incident on the dielectric discharge tube, so damage due to ion bombardment is small. The inductively coupled plasma generates an electric field in the central axis direction of the cylindrical dielectric discharge tube 110 . The swirl flow can confine the plasma to the central region of the dielectric tube and maintain a stable discharge.

When a high power of several tens of kWatt or more of a low frequency of several MHz or less is applied, a strong induced electric field required for discharge cannot be formed. In order to generate a strong induction electric field, a novel induction coil structure is proposed. Induction coil and antenna have the same meaning and are used interchangeably below. In the case of an inductively coupled plasma (ICP) antenna, the intensity of the induced electric field delivered to the plasma is proportional to the current and frequency of the induction coil, and is proportional to the square of the number of turns (the number of turns). Therefore, as the number of turns of the induction coil (or antenna) increases, a high current can be applied to the plasma. However, as the number of turns of the solenoid coil increases, energy is distributed in the longitudinal direction of the dielectric discharge tube due to spatial constraints. Also, the high inductance (impedance) of the induction coil makes it difficult to transmit power from the RF generator to the induction coil (antenna). Importantly, since the density of the electric field formed around the plasma must be increased, the number of turns per unit length of the dielectric discharge tube must be maximized in the longitudinal direction. According to the experimental results, it is difficult to stably generate an inductively coupled plasma in an induction coil having a single layer structure.

Therefore, after winding the induction coil a certain number of times, we designed the induction coil to be overlapped on the outside. That is, an induction coil having a multilayer structure is proposed. The number of turns and the number of layers depend on the diameter of the dielectric discharge tube 110 and an inductance value suitable for impedance matching. For example, if a 4 turn antenna is used three times over a dielectric discharge tube with a diameter of 80mm, the antenna resistance is 180 mOhm, the antenna inductance is 8 μH, and a current of 180 A can be applied to the antenna.

The AC power supply may provide AC power in a range of 100 kHz to 4 MHz to the induction coil. Meanwhile, an impedance matching network 128 may be disposed between the AC power supply unit 129 and the induction coil 120 for impedance matching.

4A is a cut-away perspective view illustrating an induction coil having a stacked structure according to an embodiment of the present invention.

Fig. 4b is a cross-sectional view of the induction coil of Fig. 4a;

4C is a circuit diagram illustrating an induction coil of the stacked structure of FIG. 4A.

4A to 4C , the induction coil 120 may be in the form of a solenoid having a multi-layer structure. The number of layers of the induction coil 120 may be 2 to 3 layers. In addition, the number of turns of each layer may be 3 to 5.

The induction coil 120 includes a lower solenoid coil 122 disposed to surround the dielectric discharge tube 110 ; and an upper solenoid coil 126 disposed to surround the lower solenoid coil. The lower solenoid coil 122 and the upper solenoid coil 126 may be connected in series, and the direction of the magnetic field generated by the lower solenoid coil may be the same as the direction of the magnetic field generated by the upper solenoid coil.

The induction coil 120 may further include an intermediate solenoid coil 124 disposed between the lower solenoid coil 122 and the upper solenoid coil 126 . The lower solenoid coil 122 , the intermediate solenoid coil 124 , and the upper solenoid coil 126 may be connected in series. The magnetic fields generated by the lower solenoid coil 122 , the middle solenoid coil 124 , and the upper solenoid coil 126 may have the same direction. The frequency of the AC power supply may be 100 kHz to 4 MHz.

Each of the lower solenoid coil 122 , the middle solenoid coil 124 , and the upper solenoid coil 126 may include a spacer 121 surrounding the outer pipe. The spacer 121 may be an insulating material that does not melt at a high temperature and has a high dielectric breakdown voltage. The spacer may prevent contact of the induction coil and maintain a constant distance therebetween. When the distance between the induction coils is too narrow, atmospheric pressure discharge may occur. The induction coil is made of a pipe, and a refrigerant may flow therein.

According to a modified embodiment of the present invention, the induction coil may have a solenoid coil structure having a two-layer structure, and the induction coil may have 4 turns in the lower layer and 4 turns in the upper layer.

[Reduction of actual resistance of induction coil (antenna) by parallel structure]

In the case of discharging atmospheric pressure CO2/CH4 plasma, the real resistance of the plasma is sharply reduced to a level of 0.6 to 0.9 Ohm compared to an argon (Ar) plasma. Due to the decrease in the absolute value of the impedance, the amount of current required increases. At this time, a current of about several hundred amperes (A) is required. When the resistance of the device (the induction coil self-resistance or the contact resistance of the connection part) becomes negligible compared to the actual resistance of the plasma, the efficiency of transmitting power to be supplied decreases, and energy is lost to the device. Therefore, the mechanism is damaged, and the possibility of an accident arises.

The highest real resistance among devices is the antenna's own real resistance (about 0.18 Ohm). The actual resistance of the antenna may account for 80% of the total resistance of the device. Although the antenna is cooled with water to reduce the possibility of damage, the problem of energy loss remains. The energy loss of the antenna during CO2 discharge exceeds 20%, so improvement is needed. Accordingly, a parallel connection structure of antennas is proposed.

5A is a cut-away perspective view illustrating an induction coil having a parallel structure according to an embodiment of the present invention.

Fig. 5b is a cross-sectional view of the induction coil of Fig. 5a;

5C is a circuit diagram illustrating an induction coil of the stacked structure of FIG. 5A.

5A to 5C , the induction coil 430 may include induction coil modules 430a and 320b having a plurality of multilayer structures. The multi-layered induction coil modules 430a and 320b are spatially spaced apart from each other, electrically connected to each other in parallel, and magnetic fields generated by the multi-layered induction coil modules may constructively interfere with each other. The first induction coil module 320a may include a lower solenoid coil 322a, the middle solenoid coil 324a, and the upper solenoid coil 326a. The second induction coil module 320b may include a lower solenoid coil 322b, the middle solenoid coil 324b, and the upper solenoid coil 326b.

Case 1 Case 2 Case 3 3 storey structure
(10 turns) 3-layer structure + constructive interference parallel
(10 X 2 turns) 3-layer structure + constructive interference parallel
(13 X 2 turns) L = 8.1 uH
R=180 mOhm L = 6.8 uH
R=91 mOhm L = 8.9 uH
R=120 mOhm

When the antenna structure (induction coil structure) is made in parallel (case 2 and case 3), the resistance of the antenna is reduced to about 1/2, and the inductance becomes 65% of the original level. Accordingly, the impedance matching of the AC power supply has a wider range, and the antenna resistance is reduced, so that the loss is also reduced. And the number of turns can be increased due to the low inductance, so that plasma energy coupling is improved. [Gas input and swirl structure]

6 is a cut-away perspective view illustrating a swirl providing unit of a plasma apparatus according to an embodiment of the present invention.

Referring to FIG. 6 , the gas supply unit 21 may supply methane, carbon dioxide, argon, and a combination gas thereof. The gas supply unit 21 may provide different gases and flow rates according to an initial discharge mode and a main discharge mode. For example, in the initial discharge mode, the argon gas and carbon dioxide may be mainly supplied to the dielectric discharge tube 110 . Meanwhile, in the case of the main discharge mode, carbon dioxide and methane gas may be supplied to the dielectric discharge tube 100 . In addition, the initial discharge mode may be mainly discharged in a capacitive coupling mode using a high voltage, and the main discharge mode may be mainly discharged in an inductive coupling mode using a high current.

When the dielectric discharge tube 110 confines plasma, strong heat is transferred to the outer wall. Therefore, since the dielectric discharge tube 110 may be damaged by heat, it provides a strong swirl flow or swirl flow of gas on the surface of the dielectric discharge tube 110 as compared to the center of the dielectric discharge tube 110 . Accordingly, the swirl flow directs the plasma to the center and isolates it from the outer wall of the dielectric discharge tube. Accordingly, the dielectric discharge tube 110 is protected from heat. In addition, the high atmospheric pressure inhibits the transfer of thermal energy of the plasma and heated gas to the dielectric discharge tube. In order to achieve this effect, a vortex gas flow is required on the surface of the dielectric discharge tube 100 at a strong speed. In addition, a pressure difference between the center and the inner surface of the dielectric discharge tube is required. In addition, the formation of local vortices should be suppressed.

In order to rotate the gas in a desired direction, there is a swirl generator 140 that generates a vortex first. The swirl generator 140 may stably induce a swirl flow while minimizing thermal contact with the plasma by the induction coil.

1 to 3 of the conventional US 7,662,693, the plasma vessel has a double-wall structure having an outer wall and an inner wall, and a slit is formed in the inner wall to generate a swirl flow. However, this structure cannot stably generate swirl flow. In addition, the inner wall may be damaged by the heat of the plasma. In addition, when the inner wall is formed of a dielectric material, it is very difficult to manufacture the slit. In addition, when the inner wall is a conductor, the inner wall is directly heated by the induced electric field of the induction coil, and is damaged by heat.

Therefore, there is a need for another method that can stably provide swirl flow in an inductively coupled plasma. According to an embodiment of the present invention, the swirl generator 140 is coupled to one end of the dielectric discharge tube 110 to provide a swirl flow through the nozzle. The swirl flow may proceed along the dielectric discharge tube 110 while forming a vortex in the dielectric discharge tube. When the swirl generator 140 and the induction coil 120 are disposed close to each other (for example, several centimeters or less), strong thermal energy generated by the induction coil 120 is applied to the swirl generator 140 . ) may be damaged. Accordingly, the swirl generator 140 and the induction coil 120 may be separated by several centimeters or more.

The swirl generator 140 is designed by subdividing the nozzle for optimizing the position control and reaction of the atmospheric pressure plasma. Accordingly, the discharge stability of the plasma and the reaction efficiency of the gas were improved. The nozzle includes an outer nozzle 143a and an inner nozzle 144a. Alternatively, the nozzle may include an outer nozzle 1443a , an inner nozzle 144a , and a center nozzle 145 . The outer nozzle 143a may receive gas through the outer nozzle gas supply line 141a. The inner nozzle 144a may receive gas through the inner nozzle gas supply line 141b. The central nozzle 145 may receive gas through the central nozzle gas supply line 141c.

The swirl generator 140 may include an outer nozzle 143a providing an outer swirl flow and an inner nozzle 144a providing an inner swirl flow.

In addition, according to a modified embodiment of the present invention, the swirl generator 140 has an outer nozzle 143a providing an outer swirl flow, an inner nozzle 144a providing an inner swirl flow, and a gas without swirl in the center. It may include a central nozzle 145 for injecting. The supply of gas through the central nozzle 145 may suppress contact between the dielectric discharge tube 110 and plasma and improve plasma stability.

When only the outer nozzle 143a is used to provide the swirl flow, plasma stability is deteriorated, and the plasma may come into contact with the inner wall of the dielectric discharge tube. Accordingly, when the inner nozzle 144a is additionally disposed, plasma stability may be improved.

The swirl generating unit 140 divides the region into two or three parts from the center to the edge with respect to the concentric circle of the dielectric discharge tube and injects the gas. The outer nozzle 143a provides a swirl flow to isolate the cooling and plasma to the inner edge of the dielectric discharge tube. An inner nozzle 144a for adjusting a pressure difference is positioned between the center nozzle 145 and the outer nozzle 143a. The inner nozzle 144a may adjust a pressure difference in a radial direction of the dielectric discharge tube.

The inner nozzle 143a and the outer nozzle 144a may provide a swirl flow by discharging a gas containing carbon dioxide as a main component. The central nozzle 145 may discharge a gas for a reaction (eg, a gas containing methane as a main component).

The swirl generator 140 and the induction coil 120 may be disposed to be spaced apart from each other by several centimeters or more. In this case, if the distance between the swirl generating unit 140 and the induction coil 120 is sufficiently spaced apart to suppress heating of the swirl generating unit 140, the swirl flow will not continue until the plasma generating region. can That is, the swirl guide 112 is disposed to continue the swirl flow up to the region where the induction coil is disposed.

The swirl guide 112 may have a cylindrical shape and be disposed to be inserted into one end of the dielectric discharge tube to form a concentric structure. Specifically, the swirl guide 112 may be mounted on the swirl generator 140 and extend in a central axis direction of the dielectric discharge tube 112 . Accordingly, the fluid having an azimuth velocity component supplied between the dielectric discharge tube and the swirl guide may stably provide a swirl flow. The swirl guide 112 may be short so as not to reach the discharge region where plasma is generated by the induction coil. When the swirl guide 112 extends to the discharge region, plasma may thermally damage the swirl guide 112 . The swirl guide 112 may be made of a dielectric material such as quartz, ceramic, or sapphire. Also, the swirl guide 112 and the dielectric discharge tube 110 may have a concentric structure in which their central axes coincide. The swirl guide 112 may provide a friction force to stably form an outer swirl flow by the outer nozzle and an inner swirl flow by the inner nozzle. In addition, the swirl guide 112 serves as a guide for guiding the gas flow at the edge as desired, and reduces the exposure of plasma to the conductor surface of the gas nozzle. In the absence of the swirl guide, it is difficult to maintain stable plasma.

The swirl generator 140 includes: an outer nozzle 143a periodically disposed on a circumference of a certain radius along the inner wall of the dielectric discharge tube and providing a swirl flow; and an inner nozzle 144a that is periodically disposed on a circumference of a constant radius on the inside of the outer nozzle and provides a swirl flow. The swirl guide 112 may be disposed between the inner nozzle and the outer nozzle and may have a cylindrical shape made of a dielectric material extending in the longitudinal direction of the dielectric discharge tube 110 .

Specifically, the swirl generator 140 provides a flow velocity of an azimuth direction component in a cylindrical coordinate system, is coupled to one end of the dielectric discharge tube and includes an outer injector portion 245 including a plurality of outer nozzles 143a; an outer support portion 244 coupled with the outer injector portion 245 to provide an outer buffer space 143b; an outer sealing portion 243 coupled to the outer support portion to seal the outer buffer space 143b; an inner support portion 242 inserted into the outer sealing portion 243 and providing an inner buffer space 144b; It may include an inner injector portion 248 that provides a flow rate of an azimuth direction component and is inserted into the inner support portion 242 to seal the inner buffer space and includes a plurality of inner nozzles 144a. The outer nozzle 143a may be connected to the outer buffer space 143b, and the inner nozzle 144a may be connected to the inner buffer space 144b.

The outer injector unit 245 includes a plurality of outer nozzles disposed on a circumference of a constant radius. The outer nozzles 143a are arranged inside the dielectric discharge tube with a predetermined period. The outer injector part 245 may have a ring shape having a quadrangular surface, and may have a portion extending in the central axis direction outside the ring shape. The extended portion may be disposed to surround the outer surface of the dielectric discharge tube 110 . The outer injector part 245 is coupled to the outer support part 244 .

The outer support part 244 is disposed to surround the outer surface of the outer injector part 245 , and the outer support part 244 is a depression disposed on a circumference of a certain radius to form the outer buffer space 143b . may include wealth. The outer buffer space 143b is connected to the outer nozzle 143a, and the outer nozzle 143a provides a swirl flow while proceeding in a helical direction.

The outer sealing portion 243 is disposed on the lower surface of the outer support portion 244 and is coupled to seal the outer buffer space 143b. The outer sealing part 243 may include a gas passage through which gas passes through the gas line. The gas passage may be connected to the outer buffer space 143b.

The inner support part 242 is disposed to be inserted inside the outer sealing part 243 . In addition, the inner support part 242 is disposed on the lower surface of the outer sealing part 243 . Accordingly, the inner support 243 may include a cylindrical body portion having a large diameter and a cylindrical extension portion having a small diameter extending from the center of the body portion. One end of the swirl guide 112 may be disposed between the outer surface of the extension and the inner surface of the outer support 244 . One end of the inner support 242 includes a cylindrical depression, and the inner injector 248 is inserted into the depression. One end of the extension of the inner support 242 may include a structure that has a chin and is recessed on a circumference of a certain radius, and the recessed structure may provide the inner buffer space 144b. The inner buffer space 144b is sealed by the inner injector part 248 .

The inner injector part 248 includes a plurality of the inner nozzles 144a disposed on a predetermined radius, and the inner nozzles 144a are connected to the inner buffer space 144b. The inner buffer space 144b may be connected to a fluid passage passing through the inner support 242 through an external gas line.

The central injector unit 247 may be inserted into the central axis of the inner injector 242 . The central injector unit 247 may include one central nozzle 145 . The central nozzle 145 of the central injector 247 may be connected to a central buffer space 145b formed on a central axis between the inner support 242 and the inner injector 248 . The lower support part 241 may be mounted on a lower surface of the inner support part 242 . The upper support part 246 may be disposed on the outer support part 244 to press the O-ring disposed on the outer injector 244 to maintain sealing.

In addition, in order to improve the stability of the swirl flow, an auxiliary swirl generator 170 may be disposed. The swirl generator 140 may be disposed at one end of the dielectric discharge tube 110 , and the auxiliary swirl generator 170 may be disposed at the other end of the dielectric discharge tube 110 . The swirl generating unit 140 and the auxiliary swirl generating unit 170 may provide a stable flow by providing a swirl flow in the same direction.

The auxiliary swirl generator 170 may have a toroidal shape having an inner diameter equal to that of the dielectric discharge tube 110 . Accordingly, the swirl flow may stably proceed in the central axis direction of the dielectric discharge tube 110 without being disturbed by the auxiliary swirl generating unit 170 .

Meanwhile, the auxiliary swirl generating unit 170 may additionally provide a swirl flow in the same rotational direction as that of the swirl flow provided by the swirl generating unit 140 . Accordingly, the auxiliary swirl generating unit 170 may improve the stability of the swirl flow. In addition, the main component of the gas provided by the auxiliary swirl generator 170 may be a gas participating in an endothermic reaction, such as methane. Specifically, the swirl generator 140 may provide an exothermic gas such as carbon dioxide, and heat generated by the plasma may operate the endothermic reaction of methane provided by the auxiliary swirl generator 170 . By separating the input positions of the endothermic reaction gas and the exothermic reaction gas from each other, discharge stability and reaction efficiency may be increased.

[Gas input location]

When decomposing gas by plasma, the input location and flow rate of CH4 are very important issues. CH4 can perform an endothermic reaction where it is easily separated into carbon and hydrogen gas at an appropriate temperature (930 K) or higher. Methane (CH4) tends to absorb electrons easily, so its high concentration lowers the resistance of the plasma and weakens the discharge. Therefore, after passing through the plasma generating region, when CH4 gas is injected by the auxiliary swirl generating unit 170 in the high heat portion of the plasma tail, the CH4 gas recovers heat and is separated into carbon, and decomposed carbon can combine with oxygen atoms separated from CO2 to form carbon monoxide. At this time, the efficiency is increased by the recovered heat, and the discharge can also be improved.

The swirl generator 140 may be mounted on one end of the dielectric discharge tube 110 . The auxiliary swirl generator 170 may be disposed at the other end of the dielectric discharge tube 170 . Gas generates a vortex from one end of the dielectric discharge tube 110 and may move to the other end of the dielectric discharge tube 110 . As carbon dioxide proceeds through a discharge region where plasma is generated, the carbon dioxide may be decomposed to generate carbon monoxide and heat. In this case, the generated heat may be used for an endothermic reaction for decomposing methane provided by the auxiliary swirl generator 170 . In addition, the auxiliary swirl generator 170 may provide a stable flow by generating a vortex in the same direction as the swirl generator 140 . The nozzle direction of the auxiliary swirl generator 170 may have a tangential direction component and a central axis direction. Accordingly, the methane gas discharged by the auxiliary swirl generator 170 may proceed while stably forming a vortex.

The auxiliary swirl generator 170 may include an auxiliary nozzle 173 that provides a swirl flow. The auxiliary swirl generating unit 170 may provide hydrocarbons such as methane at the rear end of the plasma generating region. The auxiliary swirl generating unit 170 has a hollow toroidal shape, a plurality of auxiliary nozzles 173 are connected to the auxiliary buffer space 174 , and the advancing direction of the auxiliary nozzle 173 is a radial component in a cylindrical coordinate system. and an azimuth direction component. Accordingly, the gas that has passed through the auxiliary nozzle 173 may provide a swirl flow.

[Cooling method]

Atmospheric pressure thermal plasma emits strong heat and radiant heat to the outside during discharge. Since there is a concern about damage due to heat of the outer wall and surrounding structures, the plasma apparatus has a new structure and function to improve this.

A silicon O-ring may be used to seal between the outer wall of the dielectric discharge tube 110 and a device (or a swirl generator or an auxiliary swirl generator). However, since the O-ring is damaged at a high temperature of 300 degrees Celsius or more, cooling of the peripheral part is required. The cooling ring 142 may be disposed to surround one end of the dielectric discharge tube 110 while contacting the lower surface of the swirl generator. The cooling ring 142 may be a water cooling jacket. The cooling ring 142 may be cooled by a refrigerant. In addition, the auxiliary cooling ring 171 may be disposed to surround the other end of the dielectric discharge tube 110 while contacting the upper surface of the auxiliary swirl generating unit 170 . The auxiliary cooling ring 171 may be cooled by a refrigerant.

According to a modified embodiment of the present invention, as a method for cooling the dielectric discharge tube 110 , a ceramic material having good thermal conductivity may mold the induction coil 120 . The induction coil 120 may be buried in a ceramic paste, and the ceramic paste may be cured to form a ceramic block. The ceramic block may be separately cooled by a cooling pipe spaced apart from the induction coil 120 and buried in the ceramic block. The ceramic block may be integrally formed by being molded to contact the dielectric discharge tube 110 to conduction cooling of the dielectric discharge tube 110 .

The external and induction coils of the dielectric discharge tube 110 generate ozone and heat problems due to high heat and high current. Accordingly, the safety case 190 is disposed to surround the induction coil 120 . The safety case 190 may have a sealed cylindrical shape. The safety case 190 includes an air inlet and an air outlet. Pressurized air injected through the air inlet cools the dielectric discharge tube and the induction coil. The exhaust equipment isolates and treats ozone from the air discharged to the air outlet.

A temperature measuring unit 196 may be disposed at the other end of the dielectric discharge tube 110 (a point where it is exhausted through the induction coil). The temperature measuring unit 196 measures the temperature of the dielectric discharge tube 110 . The temperature of the dielectric discharge tube may depend on the gas temperature therein. The measured temperature can be used for process control. In the case of plasma, when the temperature is 350 to 600 degrees Celsius based on the measurement position, atmospheric pressure discharge is stably maintained. If the temperature is lower than this range, the plasma becomes unstable and the discharge is stopped. In addition, when the temperature is too high, the dielectric discharge tube 110 and peripheral devices may be damaged. Therefore, when the temperature is too high, the alternating current power or gas supply flow rate provided to the induction coil can be controlled to maintain the temperature.

A lower portion of the auxiliary swirl generator 170 may be connected to the auxiliary chamber 182 . The auxiliary chamber may be made of a dielectric material or a metal material. The auxiliary chamber 182 may provide a space for a reaction in the case of a synthesis gas production process using methane-carbon dioxide. The length of the auxiliary chamber 182 may be several centimeters to several meters.

The auxiliary chamber 182 may be mounted in the processing vessel 180 . The processing vessel 180 may use the decomposed gas or perform a post-process for collecting a necessary gas from the decomposed gas.

[Magnetic structure for improving discharge efficiency]

7 is a cross-sectional view illustrating a magnetic flux confinement unit of a plasma apparatus according to an embodiment of the present invention.

8 is a perspective view illustrating the magnetic flux confinement unit of FIG. 7 .

7 and 8 , the magnetic structure disposed around the induction coil 120 confines a magnetic field, thereby increasing the real resistance of plasma. In order to improve coupling efficiency between the plasma and the induction coil, the magnetic field formed by the induction coil 120 needs to be concentrated inside the plasma.

The magnetic flux confinement unit 130 is disposed around the induction coil 120 to confine the magnetic flux generated by the induction coil and is formed of a magnetic material. The magnetic flux confinement unit 130 may be made of a ferrite material. The magnetic flux confinement unit 130 may generate hysteresis loss by the magnetic field formed by the induction coil 120 and heat loss due to induced current. When the magnetic flux confinement unit 130 is heated to a Curie temperature or higher, its properties may be lost. Accordingly, the magnetic flux confinement unit 130 may be cooled by the cooling pipe by transferring heat by the thermally conductive cooling plate. When the thermally conductive cooling plate 132 is a conductive plate, the thermally conductive cooling plate may have a slit 132a so that an induced current does not flow.

The magnetic flux confinement unit 130 may include a plurality of magnetic blocks 130a symmetrically disposed in a plane perpendicular to the central axis of the dielectric discharge tube 110 . The magnetic block 130a may be disposed to surround an outer surface, an upper surface, and a lower surface of the induction coil 120 . The magnetic flux block 130a may be formed of a ferrite material. The magnetic flux confinement unit 130 may confine a magnetic field or magnetic flux to increase coupling efficiency. Compared to the case where the magnetic flux confinement unit 130 is not applied, it can be seen that the plasma real resistance is increased by 50% when the magnetic flux confinement unit 130 is applied. When the actual resistance of the plasma increases, the magnitude of the current required to transmit the same power decreases, and the efficiency (the ratio of the actual power to the plasma) is also improved.

The magnetic block 130a has a cross-section of a “[” shape and may extend in a longitudinal direction. The magnetic block 130a may be inserted to surround the induction coil 120 having a multilayer structure, and the magnetic block 130a may be symmetrically disposed with respect to a central axis of the induction coil 120 . When the number of magnetic blocks 130 is increased, magnetic flux confinement efficiency is increased, but self-resistance (hysteresis loss) due to ferrite increases, and the inductance may increase.

The magnetic flux confinement unit 130 includes a magnetic block 130a disposed to surround the induction coil 120; A heat conduction plate 132 disposed on the outer surface of the magnetic block 130a to contact the magnetic block 130a to transfer the heat of the magnetic block 130a; And it is fixed to the heat conduction plate to cool the heat conduction plate It may include a cooling pipe (134). The heat conduction plate 132 may include a slit 132a that blocks the flow of the induced current generated by the induction coil 120 . The heat conduction plate 132 may be formed of a conductor. In addition, the heat conductive plate 132 and the magnetic block 130a may be fixed by a heat conductive paste 133 .

The magnetic flux confinement unit according to a modified embodiment of the present invention may be disposed to surround an outer surface, an upper surface, and a lower surface of the induction coil, and may have a toroidal shape with an open inner surface.

[Initial discharge structure]

Referring to US 7,622,694, ultra-high frequency plasma is used for initial discharge. Ultra high frequency plasma discharge requires a complex mechanical structure such as a waveguide, and the dielectric plate separating the waveguide and the discharge space is easily damaged by the high frequency plasma.

Referring to US 7,578,937, carbon arc discharge is used for initial discharge. However, as a pair of carbon electrodes are arranged in the discharging space, the support structure of the carbon electrode is complicated, and the carbon electrode is easily damaged by high heat and plasma. In particular, the carbon electrode is consumed by combining with oxygen during CF4 and CO2 discharge. Therefore, a new initial discharge structure is required.

According to an embodiment of the present invention, the initial discharge generating unit 150 is disposed around the dielectric discharge tube to provide an initial discharge.

Referring again to FIG. 3 , the initial discharge generating unit 150 includes at least one pair of initial discharge electrodes 151 disposed on the outer surface of the dielectric discharge tube 110 ; and a DC power supply unit 129 for applying a DC high voltage between the pair of initial discharge electrodes 151; include

The initial discharge electrodes 151 may be disposed to be spaced apart from each other with the induction coil 120 interposed therebetween in the central axis direction of the dielectric discharge tube 110 . Specifically, the initial discharge electrode 151 may contact the outer surface of the dielectric discharge tube 110 and may be respectively disposed above and below the induction coil 120 . The DC power supply unit 152 may apply a DC high voltage to a pair of initial discharge electrodes respectively disposed above and below the induction coil 120 . The DC power supply unit 152 may apply a high voltage pulse voltage in a band of several kHz to several tens of kHz.

[Center auxiliary dielectric tube for heat exchange]

9 is a view for explaining a plasma apparatus according to another embodiment of the present invention.

3 and 9 , the auxiliary dielectric tube 114 may be disposed at the center of the dielectric discharge tube 110 . A gas may proceed inside the auxiliary dielectric tube 114 . The auxiliary dielectric tube 114 has a cylindrical shape and may be made of quartz, ceramic, alumina, or sapphire. The auxiliary dielectric tube may receive heat generated by plasma and use it for a gas decomposition reaction. Accordingly, thermal efficiency may increase.

When CH4 is passed through the plasma, the discharge is weakened and the plasma real resistance is reduced. In order to improve this, a structure in which the input position of the gas discharged from the central nozzle is moved after the induction coil is applied.

The auxiliary dielectric tube 114 has a cylindrical shape, and the gas emitted from the center nozzle 145 may proceed in the auxiliary dielectric tube 114 . One end of the auxiliary dielectric tube 114 is coupled to the center of the swirl generator 140 , and the other end of the auxiliary dielectric tube 114 is disposed after the discharge region where plasma is generated.

CO2 emitted from the outer nozzle 143a is used for plasma discharge, and the CO2 receives energy from the plasma and is decomposed to be converted into CO, oxygen atoms, and heat. And CH4 that passes through the auxiliary dielectric tube 114 and is ejected after the arrangement area of the induction coil 120 absorbs heat emitted from the plasma while passing through the auxiliary dielectric tube 114 and is separated into carbon and hydrogen molecules. Plasma discharge itself does not interfere. Then, after passing through the auxiliary dielectric tube 114, the ejected carbon atoms and the oxygen atoms existing outside react to generate carbon monoxide. The advantage of this structure is that the discharge is not degraded by CH4 interfering with the plasma. In addition, the efficiency is improved because CH4 does not take away the energy of electrons and uses heat wasted around it.

When the auxiliary dielectric tube 114 is applied, the plasma real resistance before and after CH4 input is reduced. When CH4-CO2 mixing gas is directly introduced into the plasma, the actual resistance is reduced by 30%. However, when the auxiliary dielectric tube 114 is applied, there is no change in the resistance of the plasma before and after CH4 input. Thus, a stable plasma discharge is maintained.

10 is a view showing experimental results of a plasma generating apparatus according to an embodiment of the present invention.

Referring to FIG. 10 , the plasma apparatus of FIG. 3 was used. As the pressure increases to atmospheric pressure (760 Torr), the plasma resistance decreases sharply. When the plasma resistance is reduced, the AC power supply must pass a large amount of current. Therefore, when the plasma resistance decreases, the plasma apparatus is practically difficult to operate.

Plasma resistance when the magnetic flux confinement unit 130 is used is indicated by a rectangle. 2 Plasma resistance in the case of using induction coils of parallel stacked structure is indicated by a triangle. On the other hand, the plasma resistance when only the induction coil of the stacked structure is used is indicated by a circle.

Plasma discharge is possible by using the induction coil of the stacked structure. In addition, by adopting the parallel structure, plasma discharge stability is improved by an increase in plasma resistance, and when a magnetic flux confinement unit is used, plasma discharge stability is improved by an increase in plasma resistance.

11 is a view showing experimental results of a plasma generating apparatus according to an embodiment of the present invention.

Referring to FIGS. 9 and 11 , experimental results using the induction coil and the auxiliary dielectric tube 114 having a stacked structure are shown. Plasma seal resistances before and after introduction of CH4 through auxiliary dielectric tube 114 are shown.

When CH4 is not introduced through the auxiliary dielectric tube 114 and CH4-CO2 mixed gas is directly introduced into plasma, plasma real resistance is reduced by 30%.

However, when CH4 is introduced through the auxiliary dielectric tube 114, the plasma chamber resistance before and after CH4 is input is hardly changed. Therefore, the supply of methane gas through the auxiliary dielectric tube improves discharge stability and process capability.

In the above, the present invention has been illustrated and described with respect to specific preferred embodiments, but the present invention is not limited to these embodiments, and those of ordinary skill in the art to which the present invention pertains are It includes all of the various types of embodiments that can be implemented without departing from the technical spirit.

110: dielectric discharge tube
120: induction coil
130: magnetic flux confinement unit
140: swirl generator
150: initial discharge generating unit
170: secondary swirl generator

Claims (15)

a chamber into which gas is introduced;
a first gas supply unit for supplying a first gas;
a second gas supply unit for supplying a second gas;
An antenna disposed between the first gas supply unit and the second gas supply unit and disposed outside the chamber, for inducing plasma to a plasma induction region inside the chamber to decompose the gas supplied into the chamber; decomposition of the first gas by plasma induced by the antenna and decomposition of the second gas by plasma induced by the antenna; and
A discharging unit for discharging the decomposed first gas and the decomposed second gas; including,
The first gas includes a gas used for an exothermic reaction,
The second gas includes a gas used for an endothermic reaction,
plasma device.
According to claim 1,
The first gas supply unit introduces the first gas into the chamber at least in the longitudinal direction of the chamber,
The second gas supply unit injects the second gas into the chamber at least in a radial direction of the chamber,
plasma device.
According to claim 1,
The first gas supply unit introduces the first gas into the chamber to flow in a first direction,
The second gas supply unit injects the second gas into the chamber to flow in a second direction based on the first direction,
plasma device.
According to claim 1,
The second gas supply unit is disposed to be spaced apart from the first gas supply unit by a preset distance in the longitudinal direction of the chamber,
The preset distance is set such that the plasma induction region is formed between the first gas supply part and the second gas supply part,
plasma device.
4. The method of claim 3,
The first direction includes a central axis direction component of the chamber and a rotation direction component with respect to the central axis of the chamber,
The second direction includes a rotation direction component with respect to the central axis,
The rotation direction component of the first direction and the rotation direction component of the second direction are the same direction component,
plasma device.
4. The method of claim 3,
The first gas supply unit includes a first nozzle having a central axis direction component of the chamber and a rotation direction component with respect to the central axis of the chamber,
The second gas supply unit includes a second nozzle having a rotation direction component with respect to the central axis of the chamber,
wherein the first nozzle induces a swirl flow of the first gas and the second nozzle induces a swirl flow of the second gas,
plasma device.
delete According to claim 1,
The antenna is disposed between the first gas supply and the second gas supply,
plasma device.
9. The method of claim 8,
The antenna receives AC power from a variable frequency power source,
plasma device.
According to claim 1,
Further comprising at least one initial discharge electrode disposed on the outer surface of the chamber,
The initial discharge electrode receives a high voltage from a high voltage power supply to induce an initial discharge in the chamber,
plasma device.
11. The method of claim 10,
The initial discharge electrode is disposed between the first gas supply part and the second gas supply part,
plasma device.
12. The method of claim 11,
The initial discharge electrode is disposed between the first gas supply unit and the antenna,
plasma device.
In the gas supply method for increasing plasma stability and reaction efficiency when gas decomposition or gas synthesis is performed using an inductively coupled plasma that performs plasma discharge to decompose gas or synthesize gas,
A chamber into which gas is introduced, an antenna disposed outside the chamber to induce plasma to a plasma induction region inside the chamber to decompose the gas moving inside the chamber, and an exhaust unit for discharging the decomposed gas preparing a plasma device to
applying AC power having a variable driving frequency to the antenna;
providing a first gas to a front end of the plasma induction region through a first gas supply unit disposed at one end of the chamber;
providing a second gas to a rear end of the plasma induction region through a second gas supply unit spaced apart from the first gas supply unit by a predetermined distance in the longitudinal direction of the chamber;
inducing plasma by applying the AC power to the antenna so that the first gas and the second gas are decomposed; and
Discharging the decomposed first gas and the decomposed second gas through the discharge unit; including,
The first gas includes a gas used for an exothermic reaction,
The second gas includes a gas used for an endothermic reaction,
gas supply method.
delete 14. The method of claim 13,
and generating an initial discharge by applying a high voltage to the electrode disposed on the outer surface of the chamber prior to the step of providing the second gas.
gas supply method.

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