A non-jet atmospheric pressure thermal plasma generator

Abstract

The present invention discloses a non-jet atmospheric pressure thermal plasma generator, belonging to the technical field of microwave plasma. It includes an igniter and a microwave source, and is characterized in that: it further includes a reaction cavity, on which a gas channel I and a gas channel II are opened. The reaction cavity includes a cylindrical cavity and a conical cavity located above the cylindrical cavity. The conical cavity is communicated with the cylindrical cavity. A microwave feed port is opened on the cylindrical cavity, and the microwave source is connected to the microwave feed port. The igniter is connected to the conical cavity. The present invention can form a relatively large and uniform thermal plasma, realize the full and uniform heating of the gas to be treated, improve the reaction efficiency, and can be uniformly distributed within a set space range. It can effectively prevent the generation of destructive breakdown discharge, is easy to control the heat dissipation balance, and under the condition of minimizing heat dissipation as much as possible, ensure that the temperature of the whole generator is reasonable and the structure is stable, and realize the long-term operation stability.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave plasma, and in particular, to a non-jet atmospheric pressure thermal plasma generator. Background Art

[0002] Plasma is the fourth state of matter existence. It generally refers to a conductive gas that is ionized or possibly partially ionized, including six typical particles: namely electrons, positive ions, negative ions, excited atoms or molecules, ground state atoms or molecules, and photons. Whether it is partially ionized or completely ionized, the total number of negative charges is equal to the total number of positive charges, so it is called plasma, which is overall electrically neutral within the time and space range of the macroscopic scale. A more precise definition is: Plasma is a substance aggregate that is composed of electrons, positive ions, and neutral particles and is overall electrically neutral. Plasma is divided into two major categories according to temperature: high-temperature plasma and low-temperature plasma. High-temperature plasma is plasma that is completely ionized at a temperature between 10 8 -10 9 K, such as the sun, stars, and nuclear fusion plasma. And low-temperature plasma is further divided into thermal plasma and cold plasma. Thermal plasma exists in an environment with a relatively high pressure, at 1 atmospheric pressure or above, with a temperature range of 10 3 -10 5 K, and the electron temperature is approximately equal to the gas temperature, so it is also called "equilibrium plasma", such as atmospheric pressure arc discharge plasma, high-frequency induction plasma, and combustion plasma; cold plasma usually exists under low pressure or atmospheric pressure. Although the electron temperature range is still as high as 10 3 -10 4 K, the average gas temperature range is as low as 300 - 400K, and the electron temperature is much higher than the gas temperature, so it is also called "non-equilibrium plasma", such as DC glow discharge or high-frequency induction glow discharge plasma under low pressure.

[0003] Plasma has unique physical and chemical properties: it has electrical conductivity similar to that of metals, is overall electrically neutral and can be affected by magnetic fields; it has a high temperature and large particle kinetic energy; its chemical properties are active and it is prone to chemical reactions; it has unique luminescence characteristics, etc. The fundamental reason for plasma to possess these properties can be attributed to the collisions, excitations, dissociations, and ionizations between electrons and gas molecules, which generate chemically active species or groups with unpaired electrons. It is precisely due to its unique properties in aspects such as optics, electricity, mechanics, thermotics, and chemistry that plasma technology has become an emerging technology and has been widely applied. Due to containing a sufficient number of free charged particles, its behavior is significantly affected by electromagnetic forces, and overall it presents a non-condensed system that is electrically neutral. Plasma has all electromagnetic characteristics, and its behavior is different from that of ordinary solids, liquids, and gases in many aspects. The main characteristics are: there are long-range Coulomb force interactions between particles, and its motion is closely coupled with the motion of electromagnetic fields, and there are rich collective effects and collective motion modes.

[0004] Generally, high-temperature plasmas are not included in the scope of conventional industrial applications and related research, while low-temperature plasmas have more extensive applications and application values in this field. Within the scope of low-temperature plasmas, traditional theory holds that the plasmas required for chemical reactions should be non-equilibrium plasmas with an electron temperature much higher than the gas temperature, that is, low-temperature cold plasmas. It is believed that in this way, the energy of the external field can be transferred to the electrons without increasing the average energy of the reaction gas, manifested as a low average temperature. However, in actual applications, the process of chemical reactions occurring in cold plasmas is very different from traditional reactions at the same temperature, and it is not necessarily beneficial. Because the low temperature exhibited by cold plasmas is only an average concept, there are local high temperatures or some high-temperature particles inside them. Therefore, the low temperature at this time is exactly a manifestation of extremely uneven temperature; this unevenness will cause most reactants to be in the low-temperature region, far lower than the average temperature, which may affect the reaction rate and reaction speed; moreover, the local high temperature may cause irreversible damage to some reactants, generating a large number of unexpected by-products, affecting the utilization rate and yield. Thermal plasmas can provide a reaction environment with highly concentrated energy, very high temperature, and rich in highly active particles. A large number of highly active electrons, ions, atoms, and molecules in the excited state can promote many chemical reactions to occur, which not only helps to greatly increase the reaction rate but also makes some chemical reactions that are impossible at normal temperatures possible. And in an ideal thermal plasma, the electron temperature is approximately equal to the gas temperature. As long as the gas temperature is well controlled and suitable for the temperature required for chemical reactions, good reaction effects can be obtained. Although thermal plasmas have the theoretical conditions to promote chemical reactions, currently common atmospheric-pressure thermal plasma devices usually can only generate plasma torches in the state of high-speed jets, such as: DC plasma torches, high-frequency plasma torches, etc. The plasmas generated by these devices are restricted by the devices and physical conditions: the plasmas are all generated and exist in regions with extremely high energy density, in a highly concentrated state. The range of the plasma concentration region is small and the temperature is extremely high. In order to prevent the high-temperature impact or damage of the diffusion of the above-mentioned plasmas to the devices, only a large amount of low-temperature auxiliary gas can be introduced in the form of a jet to confine the plasma and blow it out directionally, thus forming a plasma jet. To achieve the above purpose, if the gas to be treated is introduced as the auxiliary gas into the plasma, its flow rate will inevitably be much larger than the plasma flow rate, and 70%-90% of the gas will not pass through the inside of the plasma and will not be sufficiently heated or ionized; if other gases are used as the auxiliary gas to blow out the plasma and send it into the gas to be treated, a large amount of useless gas will be introduced into the entire treatment system, and the effect will be even worse. Therefore, in jet plasma torch devices, it is difficult to ensure that the gas to be treated fully passes through the region where the plasma exists, and it is difficult to ensure that the gas to be treated is sufficiently heated or ionized, thus affecting the actual reaction effect.Moreover, there is a great problem of heat dissipation difficulty in concentrated high temperature, which is likely to cause the melting, gasification, and plasma ionization of the materials of the device itself, introduce impurities into the reaction system, and even damage the equipment.

[0005] In theory, microwaves can also form plasma. According to Paschen's law and the Paschen curve, it can be known that a very high electric field strength is required to break down and form plasma in normal-pressure gas; while microwaves, as a kind of electromagnetic wave, can form alternating electric and magnetic fields in space. As long as the microwave power in a unit space, that is, the microwave power density, reaches a sufficient intensity, the alternating electric field in space will reach a sufficient intensity, and it can break down normal-pressure gas to form plasma. However, in ordinary low-microwave-power-density microwave devices, the electric field strength is weak, and its distribution is also dynamic and uneven, making it difficult to form plasma. Even if plasma is formed, due to the huge change in the microwave power density distribution, the plasma cannot obtain stable energy. The migration of energy and the thermal convection of plasma and gas will cause the plasma to drift everywhere inside the microwave device, and it is extremely easy to drift and extinguish or drift to the vicinity of the microwave feed port. Since the microwave power density between the microwave feed port and the microwave source is much higher than that in the cavity, a destructive breakdown discharge will eventually occur. Increasing the microwave power density in such devices can theoretically amplify and stabilize the plasma, but in fact, since the microwave power density at the microwave feed port is even higher at this time, and the larger volume of the plasma makes it easier to drift to the vicinity of the microwave feed port, a destructive breakdown discharge will inevitably occur. In this way, it is impossible to form a stable normal-pressure thermal plasma in ordinary microwave devices.

[0006] In the prior art, among the devices capable of forming a relatively stable microwave plasma, only the microwave plasma torch in the form of a jet is available. Such a device focuses microwaves onto an extremely small dot-like area or a very short line-like area, and forms an extremely high microwave power density in this area, which causes breakdown of the atmospheric pressure gas. However, due to the excessively high local microwave power density, only a very small volume of plasma core with an extremely high temperature can be formed in a very small area and diffuses into the surrounding space. To prevent damage to the device caused by the above-mentioned high-temperature diffusion, only a large amount of auxiliary gas can be introduced in the form of a jet to confine the plasma and blow it out directionally, thereby forming a plasma jet, that is, a composite jet with a high-temperature plasma as the axis and a low-temperature gas as the sleeve. Calculated from the cross-section of this composite jet, the proportion of plasma in the composite jet is only 10%-30%. Therefore, when using a microwave plasma torch in the form of a jet to process the introduced gas, only a very small part can be effectively heated and ionized, and a large amount of gas to be processed cannot pass through the plasma region and cannot undergo an effective reaction. Moreover, the gas passing through the plasma region may undergo adverse side reactions due to excessive temperature, resulting in poor material utilization rate, processing efficiency, and processing effect, and it is difficult to be put into practical application. In addition, the addition of a large amount of auxiliary gas not only increases the processing burden of the microwave plasma device, but also increases the separation burden of the subsequent device, and at the same time reduces the reaction efficiency. Furthermore, since the plasma startup region and the subsequent continuous working region of such a device are the same region, the microwave power density in the working region is very high during low-power operation. If a high-power plasma device is required, the microwave power density, plasma temperature, and concentration in the working region will be extremely high. At this time, limited by the structure of the microwave transmission system and heat dissipation, the loadable microwave power is small and the power upper limit is low, and it is greatly restricted. In addition, if the microwave power is too large, the plasma temperature and concentration are too high, it is also difficult for the auxiliary gas to reliably confine the plasma and form a jet, which may ultimately lead to unstable operation or device damage. Therefore, such devices are also greatly restricted in industrial applications that require high efficiency, large output, and high power.

[0007] Chinese patent document with the publication number CN 105979693A and the publication date of September 28, 2016 discloses a high-power microwave plasma generating device, which is characterized in that it is composed of a microwave generator, a three-port circulator, a load, a three-pin tuner, a waveguide-to-coaxial adapter, and a torch tube. The microwave generator is connected to the three-port circulator, the three-port circulator is connected to the load and the three-pin tuner, the three-pin tuner is connected to the waveguide-to-coaxial adapter, and the waveguide-to-coaxial adapter is connected to the torch tube.

[0008] The high-power microwave plasma generating device disclosed in this patent document selects a position at least half a wavelength away from the upper end face of the torch tube at the microwave coupling position, which can prevent the overheating problem of the coaxial microwave transmission joint under high power. A structure with heat sinks is attached to the outer surface of the torch tube, further solving the problem of heat dissipation during the operation of the torch tube. It can withstand kilowatt-level power and ensure the good working state of the plasma generating device under high-power working conditions. However, a large amount of auxiliary gas is required to effectively confine and direct the plasma. A large amount of gas to be processed cannot pass through the plasma region and no effective reaction can occur; the gas passing through the plasma region may undergo adverse side reactions due to excessive temperature, resulting in poor material utilization rate, processing efficiency, and processing effect. In addition, if the microwave power is too high, the plasma temperature and concentration are too high, it is difficult for the auxiliary gas to reliably confine the plasma and form a jet, which may ultimately lead to unstable operation or device damage. Moreover, the addition of a large amount of auxiliary gas not only increases the processing burden of the microwave plasma device, but also increases the separation burden of the subsequent device, and at the same time reduces the reaction efficiency. In addition, since the plasma startup region and the subsequent continuous working region of such a device are the same region, the microwave power density in the working region is very high during low-power operation. If a high-power plasma device is required, the microwave power density, plasma temperature, and concentration in the working region will be extremely high. At this time, limited by the structure of the microwave transmission system and heat dissipation, the loadable microwave power is small and the power upper limit is low, which is greatly restricted and still cannot meet the requirements of continuous applications in the order of dozens of kilowatts, hundreds of kilowatts, and thousands of kilowatts required for industrial applications. Summary of the Invention

[0009] In order to overcome the above-mentioned defects of the prior art, the present invention provides a non-jet atmospheric pressure thermal plasma generator. The present invention can form a relatively large and uniform thermal plasma, realize the full and uniform heating of the gas to be processed, improve the reaction efficiency, and can be evenly distributed within a set space range. It can effectively prevent the occurrence of destructive breakdown discharge, is easy to control the heat dissipation balance, and ensures a reasonable temperature and stable structure of the entire generator while minimizing heat dissipation, realizing long-term operation stability.

[0010] The present invention is realized through the following technical solutions:

[0011] A non-jet atmospheric pressure thermal plasma generator, including an igniter and a microwave source, is characterized in that: it further includes a reaction cavity, the reaction cavity is provided with a gas channel I and a gas channel II, the reaction cavity includes a cylindrical cavity and a conical cavity located above the cylindrical cavity, the conical cavity is communicated with the cylindrical cavity, the cylindrical cavity is provided with a microwave feed port, the microwave source is connected to the microwave feed port, and the igniter is connected to the conical cavity.

[0012] The reaction cavity is a double-layer metal structure, including an inner cavity and an outer cavity, and a sandwich for introducing a fluid medium is formed between the inner cavity and the outer cavity.

[0013] The inner wall of the inner cavity of the conical cavity is lined with a heat insulation layer, and the thickness of the heat insulation layer is 5 - 200 millimeters.

[0014] The heat insulation layer is an alumina heat insulation layer, a zirconia heat insulation layer, a silica heat insulation layer, a silicon heat insulation layer, a graphite heat insulation layer, a silicon nitride heat insulation layer, a carbon nitride heat insulation layer or a boron nitride heat insulation layer.

[0015] A wave-transmitting partition is fixedly connected in the cylindrical cavity. The wave-transmitting partition and the cylindrical cavity form a microwave feeding area, and a microwave feeding port is located in the microwave feeding area.

[0016] A wave-transmitting mesh plate is arranged above the wave-transmitting partition. The wave-transmitting mesh plate is fixed on the inner wall of the inner cavity of the cylindrical cavity, and both the wave-transmitting mesh plate and the wave-transmitting partition are horizontally arranged.

[0017] A microwave protection air inlet for ventilating or pressurizing the microwave feeding area is arranged on the microwave source or the cylindrical cavity.

[0018] A microwave protection air outlet is opened on the cylindrical cavity. The microwave protection air outlet is located in the microwave feeding area, and an air outlet regulating valve is connected to the microwave protection air outlet.

[0019] The igniter is a high-frequency plasma torch, a chemical flame torch or a microwave plasma torch.

[0020] The taper of the conical cavity is 0.001:1 - 1000:1.

[0021] The working principle of the present invention is as follows:

[0022] In the prior art, it is difficult for a microwave device with a low microwave power density to form a plasma, the plasma is prone to drift and disperse, it is easy to cause breakdown of the microwave feeding port, and the plasma cannot be maintained stably. For a jet-type microwave plasma torch, both the excitation and the existence of the plasma are in the same high microwave power density region, with a high temperature, a large amount of auxiliary gas needs to be introduced for confinement and orientation, the reaction rate of the introduced gas is low, the power is small, and it is difficult to be applied industrially. Compared with the above two, the microwave plasma of the present invention can stably exist in a reaction cavity with a relatively low microwave power density.

[0023] After the present invention uniquely adopts the reaction cavity structure with a conical cavity, it has little impact on the microwave power density distribution in the reaction cavity, and effectively combines the microwave principle with the buoyancy principle and its motion law of the fluid under the temperature difference condition. Even when a relatively small plasma is formed under the condition of low microwave power density, due to the temperature rise and density change, under the action of buoyancy, it can drift upward and converge at the top of the conical cavity without introducing an auxiliary gas high-speed jet for restraint control, without moving around, so that the temperature condition for the plasma to survive can be maintained, and it will not disperse and extinguish.

[0024] More importantly, due to the structure of the conical cavity with a small top and a large bottom, while maintaining the convergence of the plasma, it does not limit the volume change of the plasma. It can freely expand with the increase of the input microwave power density, so that a large-volume plasma is obtained; although the volume of the plasma aggregated in the conical cavity will increase with the increase of the microwave power density, the projected area of the conical space occupied by the plasma expands according to the square of the corresponding diameter. Therefore, the expansion of the plasma in the vertical direction is small. As long as the size of the conical cavity matches the total input microwave power, that is, it is large enough, the plasma will not drift into the cylindrical cavity of the reaction cavity; furthermore, the microwave power density in the cylindrical cavity of the reaction cavity is lower, and it cannot provide enough electric field strength for the plasma to exist in this area. Based on this, the device structure of the present invention can simply and effectively control the stable existence of the plasma without adding an auxiliary gas jet to restrain the plasma, and it will not diffuse to the microwave feeding area and the microwave feeding port, and will not cause destructive breakdown discharge, ensuring the long-term stable operation of the device.

[0025] At the same time, since the plasma is effectively controlled in the conical cavity and has a good absorption effect on microwaves, it can be loaded by the microwave as a whole and uniformly and flow at a relatively low speed. Therefore, the plasma temperature is relatively uniform. It is known through testing that the temperature difference in different regions is within ±50°C of the average temperature; in addition, since there is no need for an auxiliary gas to restrain the plasma, there will be no large amount of low-temperature gas surrounding the plasma. Only the part of the plasma in contact with the cavity wall or the heat insulation layer has a relatively low temperature, but due to the heat preservation effect, the temperature will not be too low, and from the cross-section of the conical cavity, it is only a very thin annular region, accounting for less than 5%; therefore, the plasma proportion in the region where the plasma exists is as high as more than 95%.

[0026] The beneficial effects of the present invention are mainly manifested in the following aspects:

[0027] 1. The present invention: A gas channel I and a gas channel II are opened on a reaction cavity. The reaction cavity includes a cylindrical cavity and a conical cavity located above the cylindrical cavity. The conical cavity is communicated with the cylindrical cavity. A microwave feed port is opened on the cylindrical cavity, and a microwave source is connected to the microwave feed port. An igniter is connected to the conical cavity. By uniquely adopting the reaction cavity structure with a conical cavity, the microwave principle is effectively combined with the buoyancy principle and the movement law of fluid under temperature difference conditions. Even when a relatively small plasma is formed under the condition of low microwave power density, due to temperature rise and density change, under the action of buoyancy, it can drift upward and converge at the top of the conical cavity without introducing an auxiliary gas high-speed jet for restraint control, and will not move around, so that the temperature condition for the existence of the plasma can be maintained, and it will not disperse and extinguish; more importantly, due to the structure of the conical cavity with a smaller upper part and a larger lower part, while maintaining the convergence of the plasma, it does not limit the volume change of the plasma, and can freely expand with the increase of the input microwave power density, so that a large-volume plasma is obtained; although the volume of the plasma aggregated in the conical cavity will increase with the increase of the microwave power density, the projected area of the conical space occupied by the plasma expands according to the square of the corresponding diameter, so the expansion of the plasma in the vertical direction is small. As long as the size of the conical cavity matches the total input microwave power, that is, the conical cavity is large enough, the plasma will not drift into the cylindrical cavity of the reaction cavity; moreover, the microwave power density in the cylindrical cavity of the reaction cavity is lower, and it cannot provide enough electric field strength for the plasma to exist in this area. Based on this, the device structure of the present invention can simply and effectively control the stable existence of the plasma without adding an auxiliary gas jet to restrain the plasma, and does not diffuse to the microwave feeding area and the microwave feed port, and will not cause destructive breakdown discharge, ensuring the long-term stable operation of the device. The gas can be introduced through gas channel I and discharged through gas channel II, or introduced through gas channel II and discharged through gas channel I, so that the gas to be treated passes through the plasma region in the reaction cavity at a low speed and uniformly. There are three technical means, namely: First, when the reaction cavity structure, especially the conical cavity, remains unchanged and the input microwave power remains unchanged, adjust the flow rate of the gas to be treated passing through the plasma region. Increasing the flow rate can increase the volume of the plasma and decrease the temperature, and decreasing the flow rate can decrease the volume of the plasma and increase the temperature; Second, when the reaction cavity structure and the taper of the conical cavity remain unchanged and the flow rate of the gas to be treated remains unchanged, adjust the magnitude of the input microwave power. Increasing the microwave power can increase the volume of the plasma and increase the temperature, and decreasing the microwave power can decrease the volume of the plasma and decrease the temperature; Third, when the flow rate of the gas to be treated remains unchanged, replace the conical cavity with different tapers. Decreasing the taper can reduce the amplitude and speed of the plasma volume increase and decrease and increase the amplitude and speed of the plasma temperature increase and decrease when the input microwave power changes, and increasing the taper can increase the amplitude and speed of the plasma volume increase and decrease and decrease the amplitude and speed of the plasma temperature increase and decrease when the input microwave power changes.In addition, the above three technical means can be comprehensively adopted. By adjusting the gas flow rate passing through the plasma region, adjusting the input microwave power, and changing the taper of the conical cavity, and combining with the requirements of the material to be processed, the plasma volume and temperature can be conveniently and effectively adjusted to meet the actual application needs. In addition, different from the jet microwave plasma torch, the conical cavity is a system with a relatively low microwave power density and is not restricted by the microwave transmission system. According to the maximum input microwave power, the conical cavity can be enlarged and lengthened, or reduced and shortened, and a large-volume microwave plasma device with a single unit of 1kW - 1000kW or even higher microwave power can be formed. Compared with the prior art, it can achieve sufficient and uniform heating of the gas to be processed, improve the reaction efficiency, form a large and uniform thermal plasma, effectively prevent the occurrence of destructive breakdown discharge, and ensure the long-term operation stability of the entire generator. Therefore, the device of the present invention not only has rich adjustment means, is easy to control, and is easy to engineer, but also can meet the needs of large-scale industrial production.

[0028] Second, in the present invention, the reaction cavity has a double-layer metal structure, including an inner cavity and an outer cavity. A sandwich for introducing a fluid medium is formed between the inner cavity and the outer cavity, and a gas or liquid that does not react with the reaction cavity, such as air, nitrogen, water, or heat-conducting oil, can be introduced into the sandwich to achieve constant temperature adjustment. That is, when the temperature is low, the flow rate of the gas or liquid is zero, which can play a heat preservation role; when the temperature is high, the flow rate of the gas or liquid is increased, which can play a heat dissipation role, thereby effectively avoiding the excessive temperature of the cavity wall metal and losing strength. A large-scale high-power device can be manufactured to meet the needs of large-scale industrial production.

[0029] Third, in the present invention, a heat insulation layer is lined on the inner wall of the inner cavity of the conical cavity, and the thickness of the heat insulation layer is 5 - 200 mm. Selecting this specific thickness of the heat insulation layer is mainly to reduce the energy dissipation of the plasma while meeting the requirements that a small plasma device with a relatively small power can use a thinner heat insulation layer to reduce the device volume, improve the integration degree, and improve the start-up convenience; and a large plasma device with a relatively large power can use a larger thickness to greatly reduce the heat conduction speed to the outside, reduce the energy that needs to be taken away by heat dissipation, reduce the flow rate of the fluid introduced into the double-layer metal structure of the reaction cavity, and make it easier to control the temperature of the reaction cavity; thus, while minimizing the system heat dissipation, effectively avoiding the excessive temperature of the inner cavity wall metal and losing strength. At the same time, since the metal strength is guaranteed, the strength and tightness of the entire reaction cavity can be effectively guaranteed, enabling the generator of the present invention to be safely applicable to high-temperature treatment, flammable and explosive material treatment, toxic and harmful material treatment, and chemical production, with broad application prospects.

[0030] IV. In the present invention, the heat insulation layer is an alumina heat insulation layer, a zirconia heat insulation layer, a silica heat insulation layer, a silicon heat insulation layer, a graphite heat insulation layer, a silicon nitride heat insulation layer, a carbon nitride heat insulation layer or a boron nitride heat insulation layer. Using these heat insulation materials not only has high temperature resistance, but also can maintain good physical and chemical stability under high temperature conditions, without cracking, falling off, or decomposing, and without polluting the gas to be treated, thereby reducing subsequent treatment processes and production costs.

[0031] V. In the present invention, a wave-transmitting partition is fixedly connected inside the cylindrical cavity. The wave-transmitting partition and the cylindrical cavity form a microwave feeding area, and the microwave feeding port is located in the microwave feeding area. By setting the wave-transmitting partition to isolate a relatively sealed microwave feeding area, it can effectively prevent the plasma from diffusing into the microwave feeding area, thereby avoiding destructive breakdown discharge caused by the plasma near the microwave feeding port.

[0032] VI. In the present invention, a wave-transmitting mesh plate is arranged above the wave-transmitting partition. The wave-transmitting mesh plate is fixed on the inner wall of the inner cavity of the cylindrical cavity. Both the wave-transmitting mesh plate and the wave-transmitting partition are horizontally arranged. When the gas to be treated is introduced through Gas Channel I and discharged through Gas Channel II, it can evenly disperse the introduced gas to be treated and make it continue to move upward at a relatively low flow rate. Since the flow rate of the gas to be treated is low, it can evenly enter the plasma region without causing a large disturbance to the plasma, ensuring the stability of the plasma treatment of the gas to be treated.

[0033] VII. In the present invention, a microwave protection air inlet for ventilating or pressurizing the microwave feeding area is provided on the microwave source or the cylindrical cavity. Gas is introduced into the microwave feeding area through the microwave protection air inlet. The introduced gas can cool the microwave feeding area, prevent the influence of plasma and thermal radiation on the microwave feeding area, ensure a relatively high gas breakdown strength in the microwave feeding area, thereby ensuring that no destructive breakdown discharge occurs and guaranteeing the continuous and stable input of microwaves.

[0034] VIII. In the present invention, a microwave protection air outlet is opened on the cylindrical cavity. The microwave protection air outlet is located in the microwave feeding area, and an air outlet regulating valve is connected to the microwave protection air outlet. When the gas is discharged from the microwave protection air outlet, by adjusting or closing the air outlet regulating valve of the microwave protection air outlet, the gas pressure in the microwave feeding area can be increased, thereby further increasing the breakdown strength of the microwave feeding area.

[0035] IX. In the present invention, the taper of the conical cavity is 0.001:1 - 1000:1. Without changing the flow rate of the gas to be processed, it can meet the need to replace conical cavities with different tapers. Reducing the taper can, when the input microwave power changes, reduce the amplitude and speed of the increase and decrease of the plasma volume and increase the amplitude and speed of the increase and decrease of the plasma temperature. Increasing the taper can, when the input microwave power changes, increase the amplitude and speed of the increase and decrease of the plasma volume and reduce the amplitude and speed of the increase and decrease of the plasma temperature, which can increase the control means for the plasma and meet the actual application needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention will be further specifically described below in conjunction with the drawings in the specification and the specific embodiments, where:

[0037] Figure 1 is a schematic structural diagram of the present invention;

[0038] Figure 2 is a schematic structural diagram of Embodiment 5 of the present invention;

[0039] Reference numerals in the drawings: 1, igniter; 2, conical cavity; 3, microwave source; 4, microwave feed port; 5, gas passage I; 6, gas passage II; 7, cylindrical cavity; 8, inner cavity body; 9, outer cavity body; 10, interlayer; 11, heat insulation layer; 12, wave-transmitting partition board; 13, wave-transmitting mesh plate; 14, microwave protection air inlet; 15, microwave protection air outlet; 16, air outlet regulating valve. SPECIFIC EMBODIMENTS

[0040] Embodiment 1

[0041] A non-jet atmospheric pressure thermal plasma generator includes an igniter 1 and a microwave source 3, and further includes a reaction cavity. The reaction cavity is provided with a gas passage I 5 and a gas passage II 6. The reaction cavity includes a cylindrical cavity 7 and a conical cavity 2 located above the cylindrical cavity 7. The conical cavity 2 is communicated with the cylindrical cavity 7. The cylindrical cavity 7 is provided with a microwave feed port 4. The microwave source 3 is connected to the microwave feed port 4. The igniter 1 is connected to the conical cavity 2.

[0042] This embodiment is the most basic implementation mode. Gas channel Ⅰ and gas channel Ⅱ are opened on the reaction cavity. The reaction cavity includes a cylindrical cavity and a conical cavity located above the cylindrical cavity. The conical cavity is connected to the cylindrical cavity. A microwave feed port is opened on the cylindrical cavity, and a microwave source is connected to the microwave feed port. An igniter is connected to the conical cavity. By uniquely adopting the reaction cavity structure with a conical cavity, the microwave principle is effectively combined with the buoyancy principle and the movement law of fluid under temperature difference conditions. Even when a relatively small plasma is formed under the condition of low microwave power density, due to the temperature rise and density change, under the action of buoyancy, it can drift upward and converge at the top of the conical cavity without introducing an auxiliary gas high-speed jet for restraint control, and will not move around, so that the temperature condition for the plasma to survive can be maintained, and it will not disperse and extinguish. More importantly, due to the structure of the conical cavity with a small top and a large bottom, while keeping the plasma converged, it does not limit the change in the volume of the plasma, and can freely expand as the input microwave power density increases, thus obtaining a large-volume plasma. Although the volume of the plasma aggregated in the conical cavity will increase with the increase of the microwave power density, the projected area of the conical space occupied by the plasma expands according to the square of the corresponding diameter. Therefore, the expansion of the plasma in the vertical direction is small. As long as the size of the conical cavity matches the total input microwave power, that is, the conical cavity is large enough, the plasma will not drift into the cylindrical cavity of the reaction cavity. Moreover, the microwave power density in the cylindrical cavity of the reaction cavity is lower and cannot provide enough electric field strength for the plasma to exist in this area. Based on this, the device structure of the present invention can simply and effectively control the stable existence of the plasma without adding an auxiliary gas jet to restrain the plasma, and does not diffuse to the microwave feeding area and the microwave feed port, and will not cause destructive breakdown discharge, ensuring the long-term stable operation of the device. It can be introduced from gas channel Ⅰ and discharged from gas channel Ⅱ, or introduced from gas channel Ⅱ and discharged from gas channel Ⅰ, so that the gas to be treated passes through the plasma region in the reaction cavity at a low speed and uniformly. There are three technical means, namely: First, when the reaction cavity structure, especially the conical cavity, remains unchanged and the input microwave power remains unchanged, adjust the flow rate of the gas to be treated passing through the plasma region. Increasing the flow rate can increase the volume of the plasma and decrease the temperature, and decreasing the flow rate can decrease the volume of the plasma and increase the temperature. Second, when the reaction cavity structure and the taper of the conical cavity remain unchanged and the flow rate of the gas to be treated remains unchanged, adjust the size of the input microwave power. Increasing the microwave power can increase the volume of the plasma and increase the temperature, and decreasing the microwave power can decrease the volume of the plasma and decrease the temperature. Third, when the flow rate of the gas to be treated remains unchanged, replace the conical cavity with different tapers. Decreasing the taper can reduce the amplitude and speed of the plasma volume increase and decrease and increase the amplitude and speed of the plasma temperature increase and decrease when the input microwave power changes, and increasing the taper can increase the amplitude and speed of the plasma volume increase and decrease and decrease the amplitude and speed of the plasma temperature increase and decrease when the input microwave power changes.In addition, the above three technical means can be comprehensively adopted. By adjusting the gas flow rate passing through the plasma region, adjusting the input microwave power, and changing the taper of the conical cavity, combined with the requirements of the material to be processed, the plasma volume and temperature can be conveniently and effectively adjusted to meet the actual application needs. In addition, since the conical cavity is different from the jet microwave plasma torch and is a system with a relatively low microwave power density, it is not restricted by the microwave transmission system. According to the maximum input microwave power, the conical cavity can be enlarged and lengthened, or reduced and shortened, and a large-volume microwave plasma device with a single unit of 1kW - 1000kW or even greater microwave power can be formed. Compared with the existing technology, it can achieve sufficient and uniform heating of the gas to be processed, improve the reaction efficiency, form a large and uniform thermal plasma, effectively prevent the occurrence of destructive breakdown discharge, and ensure the long-term operation stability of the entire generator. Therefore, the device of the present invention not only has rich adjustment means, is easy to control, and is easy to engineer, but also can meet the needs of large-scale industrial production.

[0043] Example 2

[0044] A non-jet atmospheric pressure thermal plasma generator includes an igniter 1 and a microwave source 3, and also includes a reaction cavity. The reaction cavity is provided with a gas passage Ⅰ5 and a gas passage Ⅱ6. The reaction cavity includes a cylindrical cavity 7 and a conical cavity 2 located above the cylindrical cavity 7. The conical cavity 2 is communicated with the cylindrical cavity 7. The cylindrical cavity 7 is provided with a microwave feed port 4. The microwave source 3 is connected to the microwave feed port 4. The igniter 1 is connected to the conical cavity 2.

[0045] The reaction cavity is a double-layer metal structure, including an inner cavity body 8 and an outer cavity body 9. A sandwich layer 10 for introducing a fluid medium is formed between the inner cavity body 8 and the outer cavity body 9.

[0046] The inner wall of the inner cavity body 8 of the conical cavity 2 is lined with a heat insulation layer 11, and the thickness of the heat insulation layer 11 is 5 millimeters.

[0047] The heat insulation layer 11 is an alumina heat insulation layer.

[0048] This embodiment is a preferred embodiment. The reaction cavity is a double-layer metal structure, including an inner cavity body and an outer cavity body. A sandwich layer for introducing a fluid medium is formed between the inner cavity body and the outer cavity body, and a gas or liquid that does not react with the reaction cavity, such as air, nitrogen, water, and heat-conducting oil, can be introduced into the sandwich layer to achieve constant temperature adjustment, that is, when the temperature is low, the flow rate of the gas or liquid is zero, which can play a heat preservation role, and when the temperature is high, the flow rate of the gas or liquid is increased, which can play a heat dissipation role. Thus, it can effectively avoid the excessive temperature of the cavity wall metal and loss of strength, and large-scale high-power devices can be manufactured to meet the needs of large-scale industrial production.

[0049] The inner wall of the inner cavity of the conical cavity is lined with a heat insulation layer, and the thickness of the heat insulation layer is 5 millimeters. Selecting a heat insulation layer with this specific thickness is mainly to reduce the energy dissipation of the plasma while meeting the requirements that small plasma devices with lower power can use a thinner heat insulation layer to reduce the device volume, improve the integration degree, and enhance the start-up convenience; and large plasma devices with higher power can use a larger thickness to greatly reduce the heat conduction speed to the outside, reduce the energy that needs to be removed by heat dissipation, reduce the flow rate of the fluid introduced into the double-layer metal structure of the reaction cavity, and make it easier to control the temperature of the reaction cavity; thereby achieving minimizing the system heat dissipation while effectively preventing the metal temperature of the inner cavity from being too high and losing strength. At the same time, since the metal strength is guaranteed, the strength and sealing performance of the entire reaction cavity can be effectively ensured, enabling the generator of the present invention to be safely applicable to high-temperature treatment, flammable and explosive material treatment, toxic and harmful material treatment, and chemical production, with broad application prospects.

[0050] Example 3

[0051] A non-jet atmospheric pressure thermal plasma generator includes an igniter 1 and a microwave source 3, and also includes a reaction cavity. The reaction cavity is provided with a gas channel I 5 and a gas channel II 6. The reaction cavity includes a cylindrical cavity 7 and a conical cavity 2 located above the cylindrical cavity 7. The conical cavity 2 is communicated with the cylindrical cavity 7. A microwave feed port 4 is provided on the cylindrical cavity 7. The microwave source 3 is connected to the microwave feed port 4, and the igniter 1 is connected to the conical cavity 2.

[0052] The reaction cavity is a double-layer metal structure, including an inner cavity 8 and an outer cavity 9. A sandwich layer 10 for introducing a fluid medium is formed between the inner cavity 8 and the outer cavity 9.

[0053] The inner wall of the inner cavity 8 of the conical cavity 2 is lined with a heat insulation layer 11, and the thickness of the heat insulation layer 11 is 60 millimeters.

[0054] The heat insulation layer 11 is a zirconia heat insulation layer.

[0055] A wave-transmitting partition 12 is fixedly connected inside the cylindrical cavity 7. The wave-transmitting partition 12 and the cylindrical cavity 7 form a microwave feeding area, and the microwave feed port 4 is located in the microwave feeding area.

[0056] This embodiment is another preferred embodiment. A wave-transmitting partition is fixedly connected inside the cylindrical cavity. The wave-transmitting partition and the cylindrical cavity form a microwave feeding area, and the microwave feed port is located in the microwave feeding area. By setting the wave-transmitting partition to isolate a relatively sealed microwave feeding area, it can effectively prevent the plasma from diffusing into the microwave feeding area, thereby avoiding destructive breakdown discharge caused by the plasma near the microwave feed port.

[0057] Example 4

[0058] An atmospheric pressure thermal plasma generator without jet, comprising an igniter 1 and a microwave source 3, further comprising a reaction cavity. The reaction cavity is provided with a gas channel I 5 and a gas channel II 6. The reaction cavity comprises a cylindrical cavity 7 and a conical cavity 2 located above the cylindrical cavity 7. The conical cavity 2 is communicated with the cylindrical cavity 7. The cylindrical cavity 7 is provided with a microwave feed port 4. The microwave source 3 is connected to the microwave feed port 4. The igniter 1 is connected to the conical cavity 2.

[0059] The reaction cavity is of a double-layer metal structure, comprising an inner cavity body 8 and an outer cavity body 9. A sandwich layer 10 for introducing a fluid medium is formed between the inner cavity body 8 and the outer cavity body 9.

[0060] The inner wall of the inner cavity body 8 of the conical cavity 2 is lined with a heat insulation layer 11, and the thickness of the heat insulation layer 11 is 120 millimeters.

[0061] The heat insulation layer 11 is a silica heat insulation layer.

[0062] A wave-transmitting partition 12 is fixedly connected in the cylindrical cavity 7. The wave-transmitting partition 12 and the cylindrical cavity 7 form a microwave feeding area, and the microwave feed port 4 is located in the microwave feeding area.

[0063] Above the wave-transmitting partition 12, a wave-transmitting mesh plate 13 is arranged. The wave-transmitting mesh plate 13 is fixed on the inner wall of the inner cavity body 8 of the cylindrical cavity 7. Both the wave-transmitting mesh plate 13 and the wave-transmitting partition 12 are horizontally arranged.

[0064] The microwave source 3 is provided with a microwave protection air inlet 14 for ventilating or pressurizing the microwave feeding area.

[0065] This embodiment is another preferred embodiment. Above the wave-transmitting partition, a wave-transmitting mesh plate is arranged. The wave-transmitting mesh plate is fixed on the inner wall of the inner cavity of the cylindrical cavity. Both the wave-transmitting mesh plate and the wave-transmitting partition are horizontally arranged. When the gas to be treated is introduced from the gas channel I and discharged from the gas channel II, the introduced gas to be treated can be evenly dispersed and continue to move upward at a relatively low flow rate. Since the flow rate of the gas to be treated is low, it can enter the plasma region evenly and will not cause a large disturbance to the plasma, ensuring the stability of the plasma generation of the gas to be treated.

[0066] Example 5

[0067] An atmospheric pressure thermal plasma generator without jet, comprising an igniter 1 and a microwave source 3, further comprising a reaction cavity. The reaction cavity is provided with a gas channel I 5 and a gas channel II 6. The reaction cavity comprises a cylindrical cavity 7 and a conical cavity 2 located above the cylindrical cavity 7. The conical cavity 2 is communicated with the cylindrical cavity 7. The cylindrical cavity 7 is provided with a microwave feed port 4. The microwave source 3 is connected to the microwave feed port 4. The igniter 1 is connected to the conical cavity 2.

[0068] The reaction cavity is a double-layer metal structure, including an inner cavity 8 and an outer cavity 9. A sandwich layer 10 for introducing a fluid medium is formed between the inner cavity 8 and the outer cavity 9.

[0069] The inner wall of the inner cavity 8 of the conical cavity 2 is lined with a heat insulation layer 11, and the thickness of the heat insulation layer 11 is 200 millimeters.

[0070] The heat insulation layer 11 is a silicon heat insulation layer.

[0071] A wave-transmitting partition 12 is fixedly connected in the cylindrical cavity 7. The wave-transmitting partition 12 and the cylindrical cavity 7 form a microwave feeding area, and the microwave feeding port 4 is located in the microwave feeding area.

[0072] A wave-transmitting mesh plate 13 is arranged above the wave-transmitting partition 12. The wave-transmitting mesh plate 13 is fixed on the inner wall of the inner cavity 8 of the cylindrical cavity 7, and both the wave-transmitting mesh plate 13 and the wave-transmitting partition 12 are horizontally arranged.

[0073] The cylindrical cavity 7 is provided with a microwave protection air inlet 14 for ventilating or pressurizing the microwave feeding area.

[0074] The cylindrical cavity 7 is provided with a microwave protection air outlet 15. The microwave protection air outlet 15 is located in the microwave feeding area, and an air outlet regulating valve 16 is connected to the microwave protection air outlet 15.

[0075] The igniter 1 is a high-frequency plasma torch.

[0076] The taper of the conical cavity 2 is 0.001:1.

[0077] This embodiment is another preferred embodiment.

[0078] Embodiment 6

[0079] A non-jet atmospheric pressure thermal plasma generator includes an igniter 1 and a microwave source 3, and further includes a reaction cavity. The reaction cavity is provided with a gas passage I 5 and a gas passage II 6. The reaction cavity includes a cylindrical cavity 7 and a conical cavity 2 located above the cylindrical cavity 7. The conical cavity 2 is communicated with the cylindrical cavity 7. The cylindrical cavity 7 is provided with a microwave feeding port 4. The microwave source 3 is connected to the microwave feeding port 4, and the igniter 1 is connected to the conical cavity 2.

[0080] The reaction cavity is a double-layer metal structure, including an inner cavity 8 and an outer cavity 9. A sandwich layer 10 for introducing a fluid medium is formed between the inner cavity 8 and the outer cavity 9.

[0081] The inner wall of the inner cavity 8 of the conical cavity 2 is lined with a heat insulation layer 11, and the thickness of the heat insulation layer 11 is 200 millimeters.

[0082] The heat insulation layer 11 is a graphite heat insulation layer.

[0083] A wave - transmitting partition plate 12 is fixedly connected inside the cylindrical cavity 7. The wave - transmitting partition plate 12 and the cylindrical cavity 7 form a microwave feeding area, and the microwave feeding port 4 is located within the microwave feeding area.

[0084] Above the wave - transmitting partition plate 12, there is a wave - transmitting mesh plate 13. The wave - transmitting mesh plate 13 is fixed on the inner wall of the inner cavity body 8 of the cylindrical cavity 7. Both the wave - transmitting mesh plate 13 and the wave - transmitting partition plate 12 are horizontally arranged.

[0085] On the cylindrical cavity 7, there is a microwave protection air inlet 14 for ventilating or pressurizing the microwave feeding area.

[0086] On the cylindrical cavity 7, there is a microwave protection air outlet 15. The microwave protection air outlet 15 is located in the microwave feeding area, and an air outlet regulating valve 16 is connected to the microwave protection air outlet 15.

[0087] The igniter 1 is a chemical flame torch.

[0088] The taper of the conical cavity 2 is 0.01:1.

[0089] This embodiment is another preferred embodiment.

[0090] Embodiment 7

[0091] A non - jet atmospheric pressure thermal plasma generator includes an igniter 1 and a microwave source 3, and also includes a reaction cavity. The reaction cavity is provided with a gas passage Ⅰ5 and a gas passage Ⅱ6. The reaction cavity includes a cylindrical cavity 7 and a conical cavity 2 located above the cylindrical cavity 7. The conical cavity 2 is communicated with the cylindrical cavity 7. The cylindrical cavity 7 is provided with a microwave feeding port 4. The microwave source 3 is connected to the microwave feeding port 4, and the igniter 1 is connected to the conical cavity 2.

[0092] The reaction cavity is a double - layer metal structure, including an inner cavity body 8 and an outer cavity body 9. A sandwich layer 10 for introducing a fluid medium is formed between the inner cavity body 8 and the outer cavity body 9.

[0093] On the inner wall of the inner cavity body 8 of the conical cavity 2, there is a heat - insulating layer 11, and the thickness of the heat - insulating layer 11 is 200 millimeters.

[0094] The heat - insulating layer 11 is a silicon nitride heat - insulating layer.

[0095] A wave - transmitting partition plate 12 is fixedly connected inside the cylindrical cavity 7. The wave - transmitting partition plate 12 and the cylindrical cavity 7 form a microwave feeding area, and the microwave feeding port 4 is located within the microwave feeding area.

[0096] Above the wave - transmitting partition plate 12, there is a wave - transmitting mesh plate 13. The wave - transmitting mesh plate 13 is fixed on the inner wall of the inner cavity body 8 of the cylindrical cavity 7. Both the wave - transmitting mesh plate 13 and the wave - transmitting partition plate 12 are horizontally arranged.

[0097] A microwave protection air inlet 14 for ventilating or pressurizing the microwave feeding area is provided on the cylindrical cavity 7.

[0098] A microwave protection air outlet 15 is formed on the cylindrical cavity 7. The microwave protection air outlet 15 is located in the microwave feeding area, and an air outlet regulating valve 16 is connected to the microwave protection air outlet 15.

[0099] The igniter 1 is a microwave plasma torch.

[0100] The taper of the conical cavity 2 is 100:1.

[0101] This embodiment is another preferred embodiment.

[0102] Embodiment 8

[0103] A non-jet atmospheric pressure thermal plasma generator includes an igniter 1 and a microwave source 3, and further includes a reaction cavity. A gas passage I 5 and a gas passage II 6 are formed on the reaction cavity. The reaction cavity includes a cylindrical cavity 7 and a conical cavity 2 located above the cylindrical cavity 7. The conical cavity 2 is communicated with the cylindrical cavity 7. A microwave feed port 4 is formed on the cylindrical cavity 7. The microwave source 3 is connected to the microwave feed port 4, and the igniter 1 is connected to the conical cavity 2.

[0104] The reaction cavity is of a double-layer metal structure and includes an inner cavity body 8 and an outer cavity body 9. A sandwich layer 10 for passing a fluid medium is formed between the inner cavity body 8 and the outer cavity body 9.

[0105] A heat insulation layer 11 is lined on the inner wall of the inner cavity body 8 of the conical cavity 2, and the thickness of the heat insulation layer 11 is 200 mm.

[0106] The heat insulation layer 11 is a carbon nitride heat insulation layer.

[0107] A wave-transmitting partition plate 12 is fixedly connected in the cylindrical cavity 7. The wave-transmitting partition plate 12 and the cylindrical cavity 7 form a microwave feeding area, and the microwave feed port 4 is located in the microwave feeding area.

[0108] A wave-transmitting mesh plate 13 is arranged above the wave-transmitting partition plate 12. The wave-transmitting mesh plate 13 is fixed on the inner wall of the inner cavity body 8 of the cylindrical cavity 7, and both the wave-transmitting mesh plate 13 and the wave-transmitting partition plate 12 are horizontally arranged.

[0109] A microwave protection air inlet 14 for ventilating or pressurizing the microwave feeding area is provided on the cylindrical cavity 7.

[0110] A microwave protection air outlet 15 is formed on the cylindrical cavity 7. The microwave protection air outlet 15 is located in the microwave feeding area, and an air outlet regulating valve 16 is connected to the microwave protection air outlet 15.

[0111] The igniter 1 is a microwave plasma torch.

[0112] The taper of the conical cavity 2 is 600:1.

[0113] This embodiment is yet another preferred embodiment.

[0114] Embodiment 9

[0115] A non-jet atmospheric pressure thermal plasma generator includes an igniter 1 and a microwave source 3, and further includes a reaction cavity. A gas passage I 5 and a gas passage II 6 are formed in the reaction cavity. The reaction cavity includes a cylindrical cavity 7 and a conical cavity 2 located above the cylindrical cavity 7. The conical cavity 2 is communicated with the cylindrical cavity 7. A microwave feed port 4 is formed in the cylindrical cavity 7. The microwave source 3 is connected to the microwave feed port 4. The igniter 1 is connected to the conical cavity 2.

[0116] The reaction cavity is of a double-layer metal structure, including an inner cavity body 8 and an outer cavity body 9. A sandwich layer 10 for introducing a fluid medium is formed between the inner cavity body 8 and the outer cavity body 9.

[0117] The inner wall of the inner cavity body 8 of the conical cavity 2 is lined with a heat insulation layer 11, and the thickness of the heat insulation layer 11 is 200 mm.

[0118] The heat insulation layer 11 is a boron nitride heat insulation layer.

[0119] A wave-transmitting partition 12 is fixedly connected in the cylindrical cavity 7. The wave-transmitting partition 12 and the cylindrical cavity 7 form a microwave feeding area, and the microwave feed port 4 is located in the microwave feeding area.

[0120] Above the wave-transmitting partition 12, a wave-transmitting mesh plate 13 is arranged. The wave-transmitting mesh plate 13 is fixed on the inner wall of the inner cavity body 8 of the cylindrical cavity 7. Both the wave-transmitting mesh plate 13 and the wave-transmitting partition 12 are horizontally arranged.

[0121] A microwave protection air inlet 14 for ventilating or pressurizing the microwave feeding area is arranged on the cylindrical cavity 7.

[0122] A microwave protection air outlet 15 is formed in the cylindrical cavity 7. The microwave protection air outlet 15 is located in the microwave feeding area. An air outlet regulating valve 16 is connected to the microwave protection air outlet 15.

[0123] The igniter 1 is a high-frequency plasma torch or a chemical flame torch or a microwave plasma torch.

[0124] The taper of the conical cavity 2 is 1000:1.

[0125] This embodiment is the optimal implementation mode. Gas channel Ⅰ and gas channel Ⅱ are opened on the reaction cavity. The reaction cavity includes a cylindrical cavity and a conical cavity located above the cylindrical cavity. The conical cavity is connected to the cylindrical cavity. A microwave feed port is opened on the cylindrical cavity, and a microwave source is connected to the microwave feed port. An igniter is connected to the conical cavity. By uniquely adopting the reaction cavity structure with a conical cavity, the microwave principle is effectively combined with the buoyancy principle and the movement law of fluid under temperature difference conditions. Even when a relatively small plasma is formed under the condition of low microwave power density, due to the temperature rise and density change, under the action of buoyancy, it can drift upward and converge at the top of the conical cavity without introducing an auxiliary gas high-speed jet for restraint control, and will not move around, so that the temperature condition for the plasma to survive can be maintained, and it will not disperse and go out. More importantly, due to the structure of the conical cavity with a smaller upper part and a larger lower part, while maintaining the convergence of the plasma, it does not limit the volume change of the plasma, and can freely expand as the input microwave power density increases, thus obtaining a large-volume plasma. Although the volume of the plasma aggregated in the conical cavity will increase with the increase of the microwave power density, the projected area of the conical space occupied by the plasma expands according to the square of the corresponding diameter. Therefore, the expansion of the plasma in the vertical direction is small. As long as the size of the conical cavity matches the total input microwave power, that is, the conical cavity is large enough, the plasma will not drift into the cylindrical cavity of the reaction cavity. Moreover, the microwave power density in the cylindrical cavity of the reaction cavity is lower, and it cannot provide enough electric field strength for the plasma to exist in this area. Based on this, the device structure of the present invention can simply and effectively control the stable existence of the plasma without adding an auxiliary gas jet to restrain the plasma, and does not diffuse to the microwave feeding area and the microwave feed port, and will not cause destructive breakdown discharge, ensuring the long-term stable operation of the device. It can be introduced from gas channel Ⅰ and discharged from gas channel Ⅱ, or introduced from gas channel Ⅱ and discharged from gas channel Ⅰ, so that the gas to be treated can pass through the plasma region in the reaction cavity at a low speed and uniformly. There are three technical means, namely: First, when the reaction cavity structure, especially the conical cavity, remains unchanged and the input microwave power remains unchanged, adjust the flow rate of the gas to be treated passing through the plasma region. Increasing the flow rate can increase the volume of the plasma and decrease the temperature, and decreasing the flow rate can decrease the volume of the plasma and increase the temperature. Second, when the reaction cavity structure and the taper of the conical cavity remain unchanged and the flow rate of the gas to be treated remains unchanged, adjust the input microwave power. Increasing the microwave power can increase the volume of the plasma and increase the temperature, and decreasing the microwave power can decrease the volume of the plasma and decrease the temperature. Third, when the flow rate of the gas to be treated remains unchanged, replace the conical cavity with different tapers. Decreasing the taper can reduce the amplitude and speed of the plasma volume increase and decrease and increase the amplitude and speed of the plasma temperature increase and decrease when the input microwave power changes, and increasing the taper can increase the amplitude and speed of the plasma volume increase and decrease and decrease the amplitude and speed of the plasma temperature increase and decrease when the input microwave power changes.In addition, the above three technical means can be comprehensively adopted. By adjusting the gas flow rate passing through the plasma region, adjusting the input microwave power, and changing the taper of the conical cavity, combined with the requirements of the material to be processed, the plasma volume and temperature can be conveniently and effectively adjusted to meet the actual application needs. In addition, since the conical cavity is different from the jet microwave plasma torch and is a system with a relatively low microwave power density, it is not limited by the microwave transmission system. According to the maximum input microwave power, the conical cavity can be enlarged and lengthened or reduced and shortened, and a large-volume microwave plasma device with a single unit of 1kW - 1000kW or even greater microwave power can be formed. Compared with the prior art, it can achieve sufficient and uniform heating of the gas to be treated, improve the reaction efficiency, form a relatively large and uniform thermal plasma, effectively prevent the occurrence of destructive breakdown discharge, and ensure the long-term operation stability of the entire generator. Therefore, the device of the present invention not only has rich adjustment means, is easy to control, and is easy to engineer, but also can meet the needs of large-scale industrial production.

[0126] A microwave protection gas outlet is provided on the cylindrical cavity. The microwave protection gas outlet is located in the microwave feeding area. An outlet regulating valve is connected to the microwave protection gas outlet. When the gas is discharged from the microwave protection gas outlet, by adjusting or closing the outlet regulating valve of the microwave protection gas outlet, the gas pressure in the microwave feeding area can be increased, thereby further increasing the breakdown strength in the microwave feeding area.

Claims

1. A non-jet atmospheric pressure thermal plasma generator, comprising an igniter (1) and a microwave source (3), characterized in that: It further includes a reaction chamber, on which a gas channel I (5) and a gas channel II (6) are opened. The reaction chamber includes a cylindrical cavity (7) and a conical cavity (2) located above the cylindrical cavity (7). The conical cavity (2) is communicated with the cylindrical cavity (7). A microwave feed port (4) is opened on the cylindrical cavity (7). The microwave source (3) is connected to the microwave feed port (4). The igniter (1) is connected to the conical cavity (2). The reaction chamber is of a double-layer metal structure, including an inner cavity body (8) and an outer cavity body (9). A sandwich layer (10) for introducing a fluid medium is formed between the inner cavity body (8) and the outer cavity body (9).

2. The non-jet atmospheric pressure thermal plasma generator according to claim 1, characterized in that: The inner wall of the inner cavity body (8) of the conical cavity (2) is lined with a heat insulation layer (11), and the thickness of the heat insulation layer (11) is 5 - 200 millimeters.

3. The non-jet atmospheric pressure thermal plasma generator according to claim 2, characterized in that: The heat insulation layer (11) is an alumina heat insulation layer, a zirconia heat insulation layer, a silica heat insulation layer, a silicon heat insulation layer, a graphite heat insulation layer, a silicon nitride heat insulation layer, a carbon nitride heat insulation layer or a boron nitride heat insulation layer.

4. A non-jet atmospheric pressure thermal plasma generator according to claim 1, characterized in that: A wave-transmitting partition plate (12) is fixedly connected in the cylindrical cavity (7). The wave-transmitting partition plate (12) and the cylindrical cavity (7) form a microwave feeding area, and the microwave feed port (4) is located in the microwave feeding area.

5. The atmospheric pressure thermal plasma generator without jet according to claim 4, characterized in that: A wave-transmitting mesh plate (13) is arranged above the wave-transmitting partition plate (12). The wave-transmitting mesh plate (13) is fixed on the inner wall of the inner cavity body (8) of the cylindrical cavity (7). Both the wave-transmitting mesh plate (13) and the wave-transmitting partition plate (12) are horizontally arranged.

6. The atmospheric pressure thermal plasma generator without jet according to claim 4, characterized in that: A microwave protection air inlet (14) for ventilating or pressurizing the microwave feeding area is arranged on the microwave source (3) or the cylindrical cavity (7).

7. A non-jet atmospheric pressure thermal plasma generator according to claim 4, characterized in that: A microwave protection air outlet (15) is opened on the cylindrical cavity (7). The microwave protection air outlet (15) is located in the microwave feeding area, and an air outlet regulating valve (16) is connected to the microwave protection air outlet (15).

8. A non-jet atmospheric pressure thermal plasma generator according to claim 1, characterized in that: The igniter (1) is a high-frequency plasma torch, a chemical flame torch or a microwave plasma torch.

9. A non-jet atmospheric pressure thermal plasma generator according to claim 1, characterized in that: The taper of the conical cavity (2) is 0.001:1 - 1000:1.

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