阅读说明：本技术 复合型等离子体放电装置及利用该装置的废气处理方法 (Composite plasma discharge device and exhaust gas treatment method using same ) 是由 唐诗雅 王世强 关银霞 牟善军 刘全桢 牟洪祥 李栖楠 于 2020-06-18 设计创作，主要内容包括：本发明涉及低温等离子体技术领域,公开了一种复合型等离子体放电装置及利用该装置的废气处理方法,该复合型等离子体放电装置含有一个或多个等离子体放电反应器；所述等离子体放电反应器包括等离子体反应管(4),与所述等离子体反应管(4)同轴设置的中心高压电极(1),紧贴于等离子体反应管(4)外壁的接地电极(3)以及紧贴于等离子体反应管(4)的内壁的第二高压电极(2)。本发明提供的复合型等离子体放电装置,通过沿面放电和介质阻挡放电两种放电形式的组合或单独使用,可获得不同放电模式,满足不同种类废气降解的能量需求。(The invention relates to the technical field of low-temperature plasma, and discloses a composite plasma discharge device and an exhaust gas treatment method using the same, wherein the composite plasma discharge device comprises one or more plasma discharge reactors; the plasma discharge reactor comprises a plasma reaction tube (4), a central high-voltage electrode (1) which is coaxial with the plasma reaction tube (4), a grounding electrode (3) which is tightly attached to the outer wall of the plasma reaction tube (4) and a second high-voltage electrode (2) which is tightly attached to the inner wall of the plasma reaction tube (4). According to the composite plasma discharge device provided by the invention, different discharge modes can be obtained by combining or independently using two discharge modes of surface discharge and dielectric barrier discharge, and the energy requirements of different kinds of waste gas degradation are met.)

1. A composite plasma discharge device is characterized by comprising one or more plasma discharge reactors;

the plasma discharge reactor comprises a plasma reaction tube (4), a central high-voltage electrode (1) which is coaxial with the plasma reaction tube (4), a grounding electrode (3) which is tightly attached to the outer wall of the plasma reaction tube (4) and a second high-voltage electrode (2) which is tightly attached to the inner wall of the plasma reaction tube (4).

2. A composite type plasma discharge apparatus according to claim 1, wherein the number of the plasma discharge reactors is 2, and 2 plasma discharge reactors are connected in series or in parallel.

3. A composite type plasma discharge apparatus according to claim 2, wherein the number of the plasma discharge reactors is 3 or more, and a plurality of the plasma discharge reactors are connected in series and/or in parallel.

4. A composite plasma discharge device according to claim 1, wherein the second high voltage electrode (2) is a metal coil.

5. A composite plasma discharge device according to claim 4, wherein the second high voltage electrode (2) metal coil is arranged around the central high voltage electrode (1);

preferably, the inner diameter of the metal coil of the second high voltage electrode (2) is larger than the outer diameter of the central high voltage electrode (1).

6. A composite plasma discharge device according to claim 4, wherein the pitch of the metal coil of the second high voltage electrode (2) is 0.5-15 mm;

preferably, the pitch of the metal coil of the second high voltage electrode (2) is 1-10 mm.

7. A composite plasma discharge device according to claim 4, wherein the diameter of the second high voltage electrode (2) metal coil is 0.05-3 mm;

preferably, the diameter of the second high voltage electrode (2) metal coil is 0.1-2 mm.

8. A composite plasma discharge device according to claim 4, wherein the second high voltage electrode (2) metal coil has an electrical conductivity of 10 at 25 ℃⁵-10⁸S/m metal;

preferably, the metal is a high temperature resistant conductive metal.

9. A composite plasma discharge device according to any of claims 1-8, wherein the plasma reaction tube (4) is an insulating medium tube;

preferably, the insulating medium is quartz, ceramic, corundum, or polytetrafluoroethylene.

10. A composite plasma discharge device according to any of the claims 1-8, wherein the central high voltage electrode (1) is tubular or rod-shaped;

preferably, the tubular central high-voltage electrode (1) is an insulating medium tube, and conductive metal powder is filled in the insulating medium tube;

preferably, the insulating medium pipe is internally provided with a conductive metal rod;

preferably, the insulating medium pipe is internally provided with a conductive metal pipe;

preferably, the insulating medium tube is made of quartz, ceramic, corundum or polytetrafluoroethylene.

11. A composite plasma discharge device according to any of claims 1-8, wherein the central high voltage electrode (1) has an electrical conductivity of 10 at 25 ℃⁵-10⁸S/m metal.

12. An exhaust gas treatment method, characterized in that the treatment method employs the composite type plasma discharge apparatus according to any one of claims 1 to 11.

13. The exhaust gas treatment method according to claim 12, wherein the driving power source of the central high voltage electrode (1) is the same as or different from the driving power source of the second high voltage electrode (2).

14. The exhaust gas treatment method according to claim 13, wherein the driving power source of the central high voltage electrode (1) or the second high voltage electrode (2) is a direct current, an alternating current or a combined alternating and direct current power source.

15. The exhaust gas treatment method according to claim 14, wherein the frequency of the alternating current power source is 10Hz to 10kHz, the voltage peak is 0.1 to 50kV, and the voltage waveform is a sine wave, a pulse wave, a square wave, a triangular wave, or a sawtooth wave;

preferably, the DC power source has a positive or negative polarity and a voltage amplitude of 0.1-50 kV.

Technical Field

The invention relates to the technical field of low-temperature plasma, in particular to a composite plasma discharge device and an exhaust gas treatment method using the same.

Background

The low-temperature plasma method is a method for directly utilizing electric energy to pretreat or directly harmlessly treat toxic and harmful gases. High-voltage electric field is applied to ionize gas to generate high-chemical activity particles (including electrons, ions, free radicals, excited molecules and the like) to perform chemical reaction with waste gas molecules, so that micromolecules which are easy to degrade in a subsequent method are obtained or organic matters are directly decomposed into carbon dioxide and water. The method has the characteristics of starting and stopping immediately and simple process, and is suitable for waste gas systems with large flow and concentration fluctuation. However, the composition of actual industrial waste gas is very complicated except for H₂S, nitrogen oxides and other inorganic substances, as well as organic contaminants of a wide variety of molecular species, such as hydrocarbons, oxygen-containing organic substances, nitrogen-containing organic substances, halogen-containing organic substances, sulfur-containing organic substances, and the like. Depending on the different industrial plants and processes, the actual industrial waste gas may contain the above components simultaneously. Due to the difference of the bonding structures of the molecules, the minimum activation energy required for destroying the molecules is different, that is, the optimal electric field intensity required for each type of industrial waste gas degradation may be different, and the conventional plasma generator providing a single discharge mode cannot meet the requirement of a variable electric field.

To solve the problem, CN103418217A discloses a device for treating industrial waste gas by surface and packed bed composite discharge, which is composed of a plurality of coaxial sleeve subsystems of metal tubes and insulating medium tubes connected in series/in parallel. The coaxial sleeve subsystem comprises three electrodes (wherein the electrode outside the insulating medium tube is a high-voltage electrode, and the electrodes inside the metal outer tube and the insulating medium tube are both ground electrodes). In addition, the sleeve gap is filled with insulating particles. Therefore, two discharge areas are connected in series in the subsystem of the device, namely a creeping discharge area generated around the electrode on the inner surface of the insulating medium tube, a creeping discharge generated around the electrode on the outer surface of the insulating medium tube and a creeping-packed bed discharge area between the two tubes. The combined mode prolongs the treatment time of the waste gas, improves the treatment efficiency and realizes harmless emission. In addition, similar coaxial filling tube structured devices have also been reported in the literature (Post Plasma-Catalysis of Low Concentration VOC Over aluminum-Supported Silver Catalysts in a Surface/Packed-Bed Hybrid Discharge reader, ginger Nan (Jiang Nan), etc., Water Air Soil polar (2017)228: 113). However, the packing of the insulating particles in this packed bed area results in the voids through which the gas can pass being greatly compressed. When the gas quantity of the waste gas to be treated is the same, the gas resistance of the reactor containing the stacking particles is larger, and the pressure loss and the energy consumption of the fan are also larger compared with the reactor without stacking. The treatment flow rate of the coaxial filling sleeve structure is only 0.8L/min. This combination of devices is therefore not suitable for use in high throughput exhaust gas treatment systems, greatly limiting the range of applications involving plasma generators of this type of discharge type.

Disclosure of Invention

The invention aims to overcome the problems of single discharge mode, limited treatment capacity and the like in the prior art, and provides a composite plasma discharge device and an exhaust gas treatment method using the device. When the gas amount of the waste gas to be treated is large or pollutants which are difficult to degrade are contained, a plurality of plasma discharge reactors can be connected in series or in parallel for use, or a driving power supply is simultaneously applied to the central high-voltage electrode and the second high-voltage electrode, or the two measures are simultaneously applied, so that the energy requirement of decomposing the waste gas in unit gas amount is met; when the gas volume of the waste gas to be treated is normal or smaller, or the molecules of the pollutants to be treated are easy to decompose, the central high-voltage electrode or the second high-voltage electrode can be independently used, so that the energy consumption is reduced, and the energy utilization rate is improved. Based on this, the composite plasma discharge device and the waste gas treatment method using the device can meet various energy requirements of waste gas molecules to be treated, and are suitable for waste gas treatment with large gas quantity, complex components and large fluctuation.

In order to achieve the above object, a first aspect of the present invention provides a composite plasma discharge apparatus including one or more plasma discharge reactors;

the plasma discharge reactor comprises a plasma reaction tube, a central high-voltage electrode, a grounding electrode and a second high-voltage electrode, wherein the central high-voltage electrode is coaxially arranged with the plasma reaction tube, the grounding electrode is tightly attached to the outer wall of the plasma reaction tube, and the second high-voltage electrode is tightly attached to the inner wall of the plasma reaction tube.

Preferably, the number of the plasma discharge reactors is 2, and 2 plasma discharge reactors are connected in series or in parallel.

Preferably, the number of the plasma discharge reactors is 3 or more than 3, and a plurality of the plasma discharge reactors are connected in series and/or in parallel.

Preferably, the second high voltage electrode is a metal coil.

Preferably, the second hv electrode metal coil is arranged around the central hv electrode.

Preferably, the inner diameter of the second hv electrode metal coil is larger than the outer diameter of the central hv electrode.

Preferably, the pitch of the second high voltage electrode metal coil is 0.5-15 mm.

Preferably, the pitch of the second high voltage electrode metal coil is 1-10 mm.

Preferably, the diameter of the second high voltage electrode metal coil is 0.05-3 mm.

Preferably, the diameter of the second high voltage electrode metal coil is 0.1-2 mm.

Preferably, the second high voltage electrode metal coil has a conductivity of 10 at 25 ℃⁵-10⁸S/m metal.

Preferably, the metal is a high temperature resistant conductive metal.

Preferably, the plasma reaction tube is an insulating medium tube.

Preferably, the insulating medium is quartz, ceramic, corundum, or polytetrafluoroethylene.

Preferably, the central high voltage electrode is tubular or rod-shaped.

Preferably, the tubular central high-voltage electrode is an insulating medium tube filled with conductive metal powder.

Preferably, the insulating medium pipe is internally provided with a conductive metal rod.

Preferably, the insulating medium pipe is internally provided with a conductive metal pipe.

Preferably, the insulating medium tube is made of quartz, ceramic, corundum or polytetrafluoroethylene.

Preferably, the rod-shaped central high voltage electrode has a conductivity of 10 at 25 DEG C⁵-10⁸S/m metal.

In a second aspect, the present invention provides an exhaust gas treatment method, wherein the treatment method employs the composite plasma discharge device of the present invention.

Preferably, the driving power supply of the central high voltage electrode is the same as or different from the driving power supply of the second high voltage electrode.

Preferably, the driving power supply of the central high-voltage electrode or the second high-voltage electrode is a direct current, alternating current or alternating current-direct current composite power supply.

Preferably, the frequency of the alternating current power supply is 10Hz-10kHz, the voltage peak value is 0.1-50kV, and the voltage waveform is sine wave, pulse wave, square wave, triangular wave or sawtooth wave.

Preferably, the DC power source has a positive or negative polarity and a voltage amplitude of 0.1-50 kV.

Compared with the traditional plasma generator with a single discharge mode, the composite plasma discharge device not only provides two selectable discharge modes of creeping discharge and dielectric barrier discharge, but also provides a combined discharge mode of superposing the creeping discharge and the dielectric barrier discharge, realizes the combined action electric field distribution mode of superposing the two discharge modes, and can select the discharge mode matched with the energy to be treated according to different requirements of the energy of the molecular degradation of the waste gas to be treated, thereby increasing the effective utilization rate of the energy and improving the degradation efficiency.

According to the technical scheme, the composite plasma generating device with different discharge forms can be obtained by combining or singly using two discharge forms of creeping discharge and dielectric barrier discharge and connecting the plurality of plasma discharge reactors in series and/or in parallel, so that the energy requirement of the molecular treatment and degradation of various waste gases is met, and the composite plasma generating device is suitable for the treatment of industrial waste gases with large gas amount, complex components and large fluctuation.

Drawings

Fig. 1 is a schematic structural view of a plasma discharge reactor in a composite plasma discharge device according to the present invention;

FIG. 2 is a schematic view of discharge regions in a plasma discharge reactor according to the present invention during a creeping discharge, a dielectric barrier discharge and a creeping-dielectric barrier discharge.

Description of the reference numerals

1. A central high voltage electrode 2 and a second high voltage electrode

3. Ground electrode 4 and plasma reaction tube

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

In the present invention, the use of directional terms such as "upper, lower, left, right" generally means upper, lower, left, right in the drawings, and "inner, outer" means inner and outer of the corresponding structures, unless otherwise specified.

In the present invention, the exhaust gas includes volatile organic compounds VOCs (volatile organic compounds), which are organic compounds having a saturated vapor pressure at normal temperature of more than 70Pa and a boiling point at normal pressure of not more than 260 ℃, and the detected VOCs are about 150 or more, and further include hydrogen sulfide, dust-containing gas, flue gas, and the like.

In a first aspect, the present invention provides a hybrid plasma discharge device comprising one or more plasma discharge reactors; the plasma discharge reactor comprises a plasma reaction tube 4, a central high-voltage electrode 1 which is coaxial with the plasma reaction tube 4, a grounding electrode 3 which is tightly attached to the outer wall of the plasma reaction tube 4 and a second high-voltage electrode 2 which is tightly attached to the inner wall of the plasma reaction tube 4. Fig. 1 is a schematic structural diagram of a plasma discharge reactor according to an embodiment of the present invention. As shown in fig. 1, a central high voltage electrode 1 is disposed coaxially with a plasma reaction tube 4, a ground electrode 3 is closely attached to the outer wall of the plasma reaction tube 4, and a second high voltage electrode 2 is closely attached to the inner wall of the plasma reaction tube 4.

In the plasma discharge reactor, a dielectric barrier discharge area generated by the central high-voltage electrode and a creeping discharge area generated between the second high-voltage electrode and the plasma reaction tube simultaneously generate two types of discharge in the two areas, namely creeping-dielectric barrier composite discharge.

According to the plasma discharge reactor in the composite plasma discharge device, the two discharge forms of surface discharge and dielectric barrier discharge are used independently and/or in combination, and different discharge forms are provided at the same time, so that the energy requirements of different waste gas treatment can be met.

As shown in equation 1, sie (specific energy input) is an injection energy (unit J/L) and is one of important parameters of a plasma generator. Wherein P is the discharge power (unit W) of the plasma generator, Q is the flow rate (unit L/s) of the gas to be processed, and n is the number of the plasma generators.

In general, the removal efficiency of contaminant molecules is proportional to the amount of plasma reactor injection energy, and more refractory contaminant molecules require higher injection energy. A particular implant energy must be met to achieve a particular removal effect. Thus, a specific SIE value input can be ensured by increasing the input power when the volume of exhaust gas to be treated increases. In particular, the series/parallel connection (i.e. increasing n) or the combined superposition (i.e. increasing P) of two discharge forms of the plasma reactor₀) All the methods of (3) can increase the total power; when the concentration of pollutants or pollutant molecules which are difficult to degrade is increased, namely the SIE value is increased, and the gas quantity Q of the waste gas to be treated is constant, the total power P can be increased to ensure that the specific SIE value is input. The specific method is the same as above. When the gas volume of the waste gas to be treated is small or the molecules of the pollutants to be treated are easy to decompose, namely the SIE value is low, the central high-voltage electrode or the second high-voltage electrode can be independently used (namely the P is reduced)₀) Or the gas quantity is increased (namely Q is increased), so that the energy consumption is reduced, and the energy utilization rate is improved.

Where f in equation 2 is the applied drive power frequency (in Hz), U is the applied power voltage (in V) to the plasma generator, and I is the current (in a) through the plasma generator. In the specific implementation of the invention, in order to further utilize the existing device to realize power increase and injection energy improvement, the operation parameter of the driving power frequency f is mainly fixed in the actual operation process (because the existing device is adopted, the resistance of the device is a fixed value, and the current I is determined by the power voltage U), in order to meet the requirements of different VOCs to be processed in the specific implementation mode, on the basis of utilizing the existing coaxially arranged plasma generating device, in order to meet the degradation requirements of VOCs with different concentrations, the injection energy can be increased by increasing the peak value/amplitude value of the voltage U, so as to improve the efficiency of the plasma for processing waste gas; in another embodiment of the present invention, the drive supply frequency can be varied to effect the injection energy value; in another embodiment of the present invention, when the driving power source is a pulse power source, the duty ratio of the power input can be changed, thereby affecting the injection energy value.

In the invention, the number of the plasma discharge reactors is 2, and the 2 plasma discharge reactors are connected in series or in parallel. In a specific embodiment of the present invention, 2 plasma discharge reactors are connected in series or in parallel, and according to the difference of the waste gas to be treated, 2 plasma discharge reactors can be all in the same discharge mode (only surface discharge, only dielectric barrier discharge or surface-dielectric barrier composite discharge), and 2 plasma discharge reactors can also be in different discharge modes, for example, one plasma discharge reactor is surface discharge, and the other plasma discharge reactor is dielectric barrier discharge; or one plasma discharge reactor is in creeping discharge, and the other plasma discharge reactor is in creeping-dielectric barrier discharge; or one plasma discharge reactor is used for dielectric barrier discharge, and the other plasma discharge reactor is used for surface-dielectric barrier discharge.

In the present invention, preferably, the number of the plasma discharge reactors is 3 or more, and a plurality of the plasma discharge reactors are connected in series and/or in parallel. In one embodiment of the present invention, 3 plasma discharge reactors (respectively represented by plasma discharge reactor 1, plasma discharge reactor 2 and plasma discharge reactor 3) are included, and the 3 plasma discharge reactors are connected in series or in parallel, for example, plasma discharge reactor 1, plasma discharge reactor 2 and plasma discharge reactor 3 are connected in series or in parallel in sequence; or the plasma discharge reactor 2 and the plasma discharge reactor 3 are connected in parallel and then connected in series with the plasma discharge reactor 1. According to the difference of the waste gas to be treated, 3 plasma discharge reactors can be in the same discharge mode (only surface discharge, only dielectric barrier discharge or surface-dielectric barrier composite discharge), and 3 plasma discharge reactors can also be in different discharge modes, specifically, in the connection mode that 3 plasma discharge reactors are sequentially connected in series or 3 plasma discharge reactors are connected in parallel, the plasma discharge reactor 1 is surface discharge, and the plasma discharge reactor 2 and the plasma discharge reactor 3 are dielectric barrier discharge; or the plasma discharge reactor 1 is dielectric barrier discharge, and the plasma discharge reactor 2 and the plasma discharge reactor 3 are creeping discharge; or the plasma discharge reactor 1 is used for dielectric barrier discharge, the plasma discharge reactor 2 is used for creeping discharge, and the plasma discharge reactor 3 is used for dielectric barrier discharge; or the plasma discharge reactor 1 is creeping discharge, the plasma discharge reactor 2 is dielectric barrier discharge, and the plasma discharge reactor 3 is creeping discharge. In a connection mode of both series connection and parallel connection, the plasma discharge reactor 1 is in creeping discharge, and the plasma discharge reactor 2 and the plasma discharge reactor 3 are in dielectric barrier discharge; or the plasma discharge reactor 1 is dielectric barrier discharge, and the plasma discharge reactor 2 and the plasma discharge reactor 3 are creeping discharge; or the plasma discharge reactor 1 is used for dielectric barrier discharge, the plasma discharge reactor 2 is used for creeping discharge, and the plasma discharge reactor 3 is used for dielectric barrier discharge; or the plasma discharge reactor 1 is creeping discharge, the plasma discharge reactor 2 is dielectric barrier discharge, and the plasma discharge reactor 3 is creeping discharge. For the connection mode of more than 3 plasma discharge reactors and the specific discharge mode thereof, various selections and combinations can be made, and details are not repeated herein.

In the present invention, it is preferable that the second high voltage electrode 2 is a metal coil.

In the invention, preferably, the second high voltage electrode 2 metal coil surrounds the central high voltage electrode 1 and is attached to the inner wall of the plasma reaction tube; more preferably, the inner diameter of the metal coil of the second high voltage electrode 2 is larger than the outer diameter of the central high voltage electrode 1. As shown in fig. 1, the second high voltage electrode 2 metal coil is arranged around the central high voltage electrode 1, and the inner diameter of the second high voltage electrode 2 metal coil is larger than the outer diameter of the central high voltage electrode 1.

The pitch of the metal coil is not particularly limited, and it is sufficient that the gas discharge can be realized to generate plasma, and in the present invention, the pitch of the metal coil is preferably 0.5 to 15 mm; more preferably, the pitch of the metal coil is 1-10 mm.

The diameter of the metal coil is not particularly limited, and it is sufficient that the metal coil can generate plasma by gas discharge, and in the present invention, the diameter of the metal coil is preferably 0.05 to 3 mm; more preferably, the diameter of the metal coil is 0.1-2 mm.

The conductivity of the metal coil is not particularly limited, and the metal coil may have a conductivity of 10 at 25 ℃ as long as the metal coil can achieve the effect of influencing the strength of the electric field and the concentration of active particles generated by gas ionization⁵-10⁸S/m metal; more preferably, the metal coil has a conductivity of 10 at 25 deg.C⁷S/m metal.

In the present invention, preferably, the metal coil is a high temperature resistant conductive metal; further preferably, the metal coil is platinum, rhodium, palladium, gold, copper, tungsten, iron, and stainless steel containing nickel and titanium; still further preferably, the metal coil is iron, copper or tungsten. In one embodiment of the invention, iron coils are selected.

The plasma reaction tube is not particularly limited, and may be various reaction tubes having insulating properties, which are conventional in the art, and in the present invention, it is preferable that the plasma reaction tube 4 is an insulating medium tube; more preferably, the insulating medium is quartz, ceramic, corundum, or polytetrafluoroethylene. In one embodiment of the invention, the plasma reaction tube is a quartz tube; in another embodiment of the present invention, the plasma reaction tube is a corundum tube.

The shape of the central high voltage electrode 1 is not particularly limited, and may be various shapes conventionally used in the art, and in the present invention, the central high voltage electrode 1 is preferably tubular or rod-shaped.

The tubular central high-voltage electrode is not particularly limited, and can be various tubes with insulating performance which are conventional in the field, and in the invention, the tubular central high-voltage electrode 1 is preferably an insulating medium tube; and a conductive metal tube or conductive metal powder is filled in the insulating medium tube. In one embodiment of the invention, the insulating medium tube is filled with metal powder.

The insulating medium pipe is not particularly limited, and in the present invention, the insulating medium pipe is preferably a quartz, ceramic, corundum, or polytetrafluoroethylene pipe. In one embodiment of the invention, the insulating medium tube is a quartz tube; in another embodiment of the invention, the insulating medium pipe is a corundum pipe.

The conductive metal powder is not particularly limited, and in the present invention, it is preferable that the conductive metal powder is one or more of iron, copper, magnesium, or aluminum. In one embodiment of the present invention, iron powder is selected as the metal conductive powder (specifically, iron powder), and is filled in an insulating medium tube (specifically, a quartz tube) to serve as the central high voltage electrode. One skilled in the art can also select other metal powder with conductive performance to be filled in the insulating medium tube as the central high-voltage electrode for use according to the requirement.

In the present invention, preferably, the central high voltage electrode 1 is an insulating dielectric tube with a conductive metal rod or tube inside. In another embodiment of the invention, quartz, ceramic, corundum tube or polytetrafluoroethylene can be used as an insulating tube, and a metal rod is embedded in the insulating tube to form a central high-voltage electrode; in yet another embodiment of the present invention, a metal tube is embedded in the insulating tube as a central high voltage electrode.

The material of the metal rod or tube embedded in the insulating tube is not particularly limited, and may be, for example, 10 in electrical conductivity at 25 ℃⁵-10⁸S/m metal. In one embodiment of the present invention, an iron rod is embedded in a quartz tube to be used as a central high voltage electrode.

The tubular or rod-shaped central high voltage electrode is not particularly limited, and may be, for example, various high voltage electrodes conventional in the art, and in the present invention, preferably, the rod-shaped central high voltage electrode 1 has an electrical conductivity of 10 at 25 ℃⁵-10⁸S/m metal; more preferably, the rod-shaped central high voltage electrode 1 has an electrical conductivity of 10 at 25 ℃⁷S/m metal. In one embodiment of the invention, the central high voltage electrode 1 has a conductivity of 10 at 25 deg.C⁷S/m metal.

The ground electrode is not particularly limited, and may be, for example, a metal mesh or a metal sheet.

The working gas in the plasma discharge reactor of the present invention is not limited, and may be fixed air, nitrogen, helium, argon, etc. commonly used in the art, and one or more kinds may be selected by those skilled in the art according to actual needs.

In a second aspect, the invention provides an exhaust gas treatment method, wherein the treatment method adopts the composite plasma discharge device. Specifically, with the device shown in fig. 1, the central high voltage electrode 1 is located in the plasma reaction tube 4 and is arranged coaxially with the plasma reaction tube 4, the grounding electrode 3 is tightly attached to the outer wall of the plasma reaction tube 4, the second high voltage electrode 2 is arranged around the central high voltage electrode 1, the second high voltage electrode 2 is tightly attached to the inner wall of the plasma reaction tube 4, and the plasma reaction tube 4 is provided with gasA body inlet and a gas outlet. The central high-voltage electrode 1 and the second high-voltage electrode 2 are applied with independent power systems, different driving power supplies (including different voltages, frequencies and the like) are respectively selected, and three discharge modes can be realized: (1) when voltage is only applied to the central high-voltage electrode 1, plasma is generated in a dielectric barrier discharge mode, and the plasma is suitable for hydrocarbon such as toluene, xylene and cyclohexane; (2) when voltage is applied to the second high voltage electrode 2 only, plasma is generated in a creeping discharge mode, and the plasma is suitable for hydrocarbon derivatives such as methanol and formaldehyde; (3) when high voltage is simultaneously applied to the central high-voltage electrode 1 and the second high-voltage electrode 2, plasma is generated in a mode of creeping discharge and single dielectric barrier discharge coupling, and the plasma is suitable for the waste gas molecules which are not easily degraded in the two modes (1) and (2), such as benzene and H₂S and the like.

In the present invention, the driving power source of the center high voltage electrode 1 and the driving power source of the second high voltage electrode 2 are used separately or simultaneously. Wherein, the difference of the driving power sources means: the driving power supplies of the central high-voltage electrode 1 and the second high-voltage electrode 2 are mutually independent, and can also mean that the parameters such as voltage and/or frequency of the 2 driving power supplies are different; alternatively, the voltage may be applied only to the center high voltage electrode 1, only to the second high voltage electrode (2), or to both the first high voltage electrode and the second high voltage electrode. When the power supply is used independently, dielectric barrier discharge or creeping discharge is formed respectively, and the two high-voltage electrodes are driven simultaneously to form a creeping-dielectric barrier discharge composite electric field. FIG. 2 is a schematic view of discharge regions in a plasma discharge reactor according to the present invention during a creeping discharge, a dielectric barrier discharge and a creeping-dielectric barrier discharge. As shown in fig. 2, when only the driving power source HV1 of the center high voltage electrode 1 is used, the center high voltage electrode forms a dielectric barrier discharge, forming a dielectric barrier discharge electric field, as shown in fig. 2 a; when only the driving power supply HV2 of the second high voltage electrode is used, creeping discharge is formed between the second high voltage electrode and the plasma reaction tube, and a creeping discharge electric field is formed, as shown in FIG. 2 b; when the driving power supply HV1 and the driving power supply HV2 are used simultaneously, two forms of discharge, i.e., along-plane-dielectric barrier composite discharge, are generated simultaneously, forming an along-plane-dielectric barrier discharge composite electric field, as shown in FIG. 2 c.

The driving power source for the center high voltage electrode or the second high voltage electrode is not particularly limited, and in the present invention, the driving power source for the center high voltage electrode 1 or the second high voltage electrode 2 is preferably a dc, ac, or ac/dc hybrid power source. In one embodiment of the present invention, the driving power source of the central high voltage electrode 1 or the second high voltage electrode 2 is an ac power source.

The ac power source is not particularly limited, and in the present invention, it is preferable that the ac power source has a frequency of 10Hz to 10kHz, a voltage peak of 0.1 to 50kV, and a voltage waveform of a sine wave, a pulse wave, a square wave, a triangular wave, or a sawtooth wave. In one embodiment of the present invention, an ac power source with a frequency of 7kHz, a voltage peak of 32kV, a duty cycle of 0.3, and a sine wave waveform was used.

The dc power supply is not particularly limited, and in the present invention, the dc power supply preferably has a positive or negative polarity and a voltage amplitude of 0.1 to 50 kV. In one embodiment of the present invention, a negative polarity dc power source is used, with a voltage amplitude of 15 kV.

The present invention will be described in detail below by way of examples. In the following examples, each material used was commercially available unless otherwise specified, and the method used was a conventional method in the art unless otherwise specified.

Example 1

By adopting the device shown in fig. 1, a central high-voltage electrode 1 (specifically, a stainless steel tube, the outer diameter of which is 10mm) is positioned in a plasma reaction tube 4 (specifically, a quartz tube, the inner diameter of which is 16mm) and is coaxially arranged with the plasma reaction tube 4, an earthing electrode 3 (specifically, a copper sheet, the length of which is 10cm) is tightly attached to the outer wall of the plasma reaction tube 4, a second high-voltage electrode 2 (specifically, an iron coil, the thread pitch of which is 2mm, the outer diameter of which is 16mm) is arranged around the central high-voltage electrode 1, the second high-voltage electrode 2 is tightly attached to the inner wall of the plasma reaction tube 4, and a gas inlet and a gas outlet are arranged on the plasma reaction tube 4, wherein a high-voltage alternating current power supply is applied to the high-voltage electrode 1 and the high-voltage electrode 2, and the frequency is 7kHz and the voltage is 32 kV.

The results of treating 1L/min of exhaust gas using the above apparatus are shown in Table 1 below.

TABLE 1

Kind of exhaust gas	Discharge mode	Removal efficiency
			200ppm of toluene	Applying a voltage to the central high voltage electrode 1 only	95.8％
200ppm benzene	Applying a voltage to the central high voltage electrode 1 only	85.0％
			200ppm of formaldehyde	Applying a voltage to only the second high voltage electrode 2	80.3％
400ppm benzene	Simultaneously applying voltage to the high voltage electrodes 1 and 2	81.5％

Example 2

The same plasma discharge apparatus was used as in example 1, except that high voltages of different parameters were applied only to the center high voltage electrode 1.

The apparatus was used to treat 300ppm toluene off-gas at a flow rate of 1L/min, and the results are shown in Table 2 below.

TABLE 2

High voltage parameter	Removal efficiency
		Sine wave 7.0kHz 32kV duty cycle 1	75.0％
Sine wave 7.0kHz 38kV duty cycle 1	95.7％
		Sine wave 9.0kHz 32kV duty cycle 1	85.3％
Triangular wave 7.0kHz 32kV duty cycle 1	50.4％
		Sine wave 7.0kHz 32kV duty cycle 0.3	94.5％
Sine wave 7.0kHz 32kV duty cycle 0.5	86.5％

Example 3

The same plasma discharge apparatus as in example 1 was used, and a high voltage ac power supply, a sine wave, a frequency of 7kHz, a voltage of 34kV duty ratio of 0.3, was simultaneously applied to the high voltage electrode 1 and the high voltage electrode 2. The device is adopted to treat benzene-containing waste gas with different flow rates and the concentration of 200 ppm. The results are shown in Table 3 below.

TABLE 3

Exhaust gas flow	Removal efficiency
		1L/min	96.2％
10L/min	94.0％
		15L/min	92.0％

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.