Composite plasma discharge device and waste gas treatment method using the same

Abstract

The present invention relates to the field of low-temperature plasma technology, and discloses a composite plasma discharge device and a waste gas treatment method using the device. The composite plasma discharge device contains one or more plasma discharge reactors; the plasma discharge reactor comprises a plasma reaction tube (4), a central high-voltage electrode (1) coaxially arranged with the plasma reaction tube (4), a grounding electrode (3) closely attached to the outer wall of the plasma reaction tube (4), and a second high-voltage electrode (2) closely attached to the inner wall of the plasma reaction tube (4). The composite plasma discharge device provided by the present invention can obtain different discharge modes by combining or using two discharge forms, namely, surface discharge and dielectric barrier discharge, to meet the energy requirements for degrading different types of waste gases.

Description

Technical Field

[0001] The present invention relates to the technical field of low-temperature plasma, and in particular to a composite plasma discharge device and a waste gas treatment method using the device. Background Art

[0002] Low-temperature plasma method is a method of directly using electric energy to pre-treat or directly harmlessly treat toxic and harmful gases. By applying a high-voltage electric field to ionize the gas to produce highly chemically active particles (including electrons, ions, free radicals and excited molecules, etc.), which react chemically with waste gas molecules to obtain small molecules that are easy to degrade in subsequent methods or directly decompose organic matter into carbon dioxide and water. This method has the characteristics of instant start and stop and simple process, and is suitable for waste gas systems with large flow and concentration fluctuations. However, the actual industrial waste gas composition is very complex. In addition to inorganic substances such as H2S and nitrogen oxides, it also includes a wide variety of organic pollutants, such as hydrocarbons, oxygen-containing organic matter, nitrogen-containing organic matter, halogen-containing organic matter and sulfur-containing organic matter. Depending on different industrial devices and processes, actual industrial waste gas may contain multiple components at the same time. Due to different molecular bonding structures, the minimum activation energy required to destroy molecules is different, that is, the optimal electric field strength required for the degradation of each type of industrial waste gas may be different, and traditional plasma generators that provide a single discharge mode cannot meet the needs of variable electric fields.

[0003] To solve this problem, CN103418217A discloses a device for treating industrial waste gas by composite discharge along the surface and packed bed, which is composed of a number of coaxial sleeve subsystems of metal tubes and insulating medium tubes connected in series / parallel. The coaxial sleeve subsystem includes three electrodes (where the electrode outside the insulating medium tube is a high-voltage electrode, and the metal outer tube and the inner surface electrode of 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 device subsystem, namely the surface discharge area generated around the inner surface electrode of the insulating medium tube and the surface discharge generated around the outer electrode of the insulating medium tube and the surface-packed bed discharge area between the two tubes. This combination method prolongs the treatment time of the waste gas, improves the treatment efficiency, and achieves harmless emission. In addition, a similar coaxial filled sleeve structure device was also reported in the literature (Post Plasma-Catalysis of Low Concentration VOC Over Alumina-Supported Silver Catalysts in a Surface / Packed-Bed Hybrid Discharge Reactor, Jiang Nan et al., Water Air Soil Pollut (2017) 228: 113). However, the insulating particles stacked in the packed bed area cause the gaps through which the gas can pass to be greatly compressed. When the amount of waste gas to be treated is the same, the reactor containing the stacked particles has greater air resistance, fan pressure loss and energy consumption than the unstacked reactor. The processing flow rate of the above coaxial filled sleeve structure is only 0.8L / min. Therefore, this device combination is not suitable for large-flux waste gas treatment systems, which greatly restricts the application scope of plasma generators involving this type of discharge form. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems of single discharge mode and limited processing capacity in the prior art, and to provide a composite plasma discharge device and a waste gas treatment method using the device. The device uses two discharge forms, surface discharge and dielectric barrier discharge, separately or in superposition. At the same time, multiple plasma discharge reactors can be used in series and / or in parallel, and the sleeve gap in the reactor is a gas channel, and the gas path is straight and has no filling particle layer. When the amount of waste gas to be treated is large or contains pollutants that are difficult to degrade, multiple plasma discharge reactors can be used in series or in parallel, or a driving power supply can be applied to the central high-voltage electrode and the second high-voltage electrode at the same time, or the above two measures can be applied at the same time to meet the energy demand for the decomposition of the unit amount of waste gas; when the amount of waste gas to be treated is normal or small, or the molecules of the pollutants to be treated are easier to decompose, the central high-voltage electrode or the second high-voltage electrode can be used alone, thereby reducing energy consumption and improving energy utilization. Based on this, the composite plasma discharge device and the waste gas treatment method using the device can meet the various energy requirements of the waste gas molecules to be treated, and are suitable for the treatment of waste gas with large volume, complex composition and large fluctuations.

[0005] In order to achieve the above-mentioned object, the present invention provides a composite plasma discharge device in a first aspect, wherein the composite plasma discharge device comprises one or more plasma discharge reactors;

[0006] The plasma discharge reactor comprises a plasma reaction tube, a central high-voltage electrode coaxially arranged with the plasma reaction tube, a ground electrode closely attached to the outer wall of the plasma reaction tube, and a second high-voltage electrode closely attached to the inner wall of the plasma reaction tube.

[0007] Preferably, the number of the plasma discharge reactors is 2, and the two plasma discharge reactors are connected in series or in parallel.

[0008] Preferably, the number of the plasma discharge reactors is 3 or more, and the plurality of plasma discharge reactors are connected in series and / or in parallel.

[0009] Preferably, the second high-voltage electrode is a metal coil.

[0010] Preferably, the second high-voltage electrode metal coil is arranged around the central high-voltage electrode.

[0011] Preferably, the inner diameter of the second high-voltage electrode metal coil is greater than the outer diameter of the central high-voltage electrode.

[0012] Preferably, the pitch of the second high-voltage electrode metal coil is 0.5-15 mm.

[0013] Preferably, the pitch of the second high-voltage electrode metal coil is 1-10 mm.

[0014] Preferably, the diameter of the second high-voltage electrode metal coil is 0.05-3 mm.

[0015] Preferably, the diameter of the second high-voltage electrode metal coil is 0.1-2 mm.

[0016] Preferably, at 25°C, the second high voltage electrode metal coil has an electrical conductivity of 10 5 -10 8 S / m of metal.

[0017] Preferably, the metal is a high temperature resistant conductive metal.

[0018] Preferably, the plasma reaction tube is an insulating medium tube.

[0019] Preferably, the insulating medium is quartz, ceramic, corundum or polytetrafluoroethylene.

[0020] Preferably, the central high-voltage electrode is tubular or rod-shaped.

[0021] Preferably, the tubular central high-voltage electrode is an insulating medium tube, and the insulating medium tube is filled with conductive metal powder.

[0022] Preferably, a conductive metal rod is provided in the insulating medium tube.

[0023] Preferably, a conductive metal tube is provided inside the insulating medium tube.

[0024] Preferably, the insulating medium tube is made of quartz, ceramic, corundum or polytetrafluoroethylene.

[0025] Preferably, at 25°C, the conductivity of the rod-shaped central high voltage electrode is 10 5 -10 8 S / m of metal.

[0026] A second aspect of the present invention provides a waste gas treatment method, wherein the treatment method adopts the composite plasma discharge device described in the present invention.

[0027] Preferably, the driving power source of the central high-voltage electrode is the same as or different from the driving power source of the second high-voltage electrode.

[0028] Preferably, the driving power supply of the central high-voltage electrode or the second high-voltage electrode is a direct current, an alternating current or an AC / DC composite power supply.

[0029] Preferably, the frequency of the AC power supply is 10 Hz-10 kHz, the voltage peak is 0.1-50 kV, and the voltage waveform is a sine wave, a pulse wave, a square wave, a triangle wave or a sawtooth wave.

[0030] Preferably, the DC power supply has a positive or negative polarity and a voltage amplitude of 0.1-50 kV.

[0031] Compared with the traditional plasma generator with a single discharge mode, the composite plasma discharge device of the present invention not only provides two optional discharge forms of surface discharge and dielectric barrier discharge, but also provides a combined discharge form in which the two discharge forms are superimposed, thereby realizing a combined electric field distribution mode of the superposition of the two discharge forms, and a discharge form that matches the different energy requirements for the degradation of the waste gas molecules to be treated can be selected, thereby increasing the effective utilization rate of energy and improving the degradation efficiency.

[0032] The above technical scheme, through the combination or single use of two discharge forms, surface discharge and dielectric barrier discharge, and multiple plasma discharge reactors connected in series and / or in parallel, can obtain a composite plasma generating device with different discharge forms, thereby meeting the energy requirements for the treatment and degradation of various types of waste gas molecules, and is suitable for the treatment of large amounts of industrial waste gas with complex components and large fluctuations. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic structural diagram of a plasma discharge reactor in a composite plasma discharge device provided by the present invention;

[0034] Figure 2 It is a schematic diagram of the discharge area during surface discharge, dielectric barrier discharge and surface-dielectric barrier discharge in the plasma discharge reactor of the present invention.

[0035] Description of Reference Numerals

[0036] 1. Central high voltage electrode 2. Second high voltage electrode

[0037] 3. Ground electrode 4. Plasma reaction tube DETAILED DESCRIPTION

[0038] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0039] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0040] In the present invention, unless otherwise specified, directional words such as "up, down, left, right" generally refer to up, down, left, right in the drawings, and "inside, outside" refer to the inside and outside of the corresponding structure.

[0041] In the present invention, the waste gas includes volatile organic compounds (VOCs), which are organic compounds with a saturated vapor pressure greater than 70 Pa at room temperature and a boiling point not higher than 260°C at normal pressure. There are about 150 types of VOCs detected. In addition, it also includes hydrogen sulfide, dust-containing gas and flue gas.

[0042] In the first aspect, the present invention provides a composite plasma discharge device, which contains one or more plasma discharge reactors; the plasma discharge reactor includes a plasma reaction tube 4, a central high-voltage electrode 1 coaxially arranged with the plasma reaction tube 4, a ground electrode 3 close to the outer wall of the plasma reaction tube 4, and a second high-voltage electrode 2 close to the inner wall of the plasma reaction tube 4. Figure 1 Schematic diagram of the structure of a plasma discharge reactor provided by one embodiment of the present invention. Figure 1 As shown, the central high-voltage electrode 1 located in the center is coaxially arranged with the plasma reaction tube 4 , the ground electrode 3 is closely attached to the outer wall of the plasma reaction tube 4 , and the second high-voltage electrode 2 is closely attached to the inner wall of the plasma reaction tube 4 .

[0043] In the plasma discharge reactor of the present invention, the dielectric barrier discharge area generated by the central high-voltage electrode and the surface discharge area generated between the second high-voltage electrode and the plasma reaction tube simultaneously generate two forms of discharge in the two areas, namely, surface-dielectric barrier composite discharge. The plasma discharge device including the plasma discharge reactor is a composite plasma discharge device.

[0044] The plasma discharge reactor in the composite plasma discharge device of the present invention can meet the energy requirements of different waste gas treatments by using two discharge forms, namely, surface discharge and dielectric barrier discharge, separately and / or in combination, and providing different discharge forms.

[0045]

[0046] As shown in Formula 1, SIE (specific energy input) is the injected energy (unit J / L), which is one of the important parameters of the plasma generator. Among them, P is the discharge power of the plasma generator (unit W), Q is the flow rate of the gas to be treated (unit L / s), and n is the number of plasma generators.

[0047] In general, the removal efficiency of pollutant molecules is proportional to the injection energy value of the plasma reactor, and the more difficult the pollutant molecules are to degrade, the higher the injection energy required. If you want to obtain a specific removal effect, you must meet a specific injection energy. Therefore, when the volume of waste gas to be treated increases, a specific SIE value input can be guaranteed by increasing the input power. Specifically, the total power can be increased by connecting plasma reactors in series / parallel (i.e., increasing n) or combining two discharge forms (i.e., increasing P0); when the concentration of pollutants or pollutant molecules that are difficult to degrade increases, that is, the SIE value increases, and the amount of waste gas to be treated Q is constant, the total power P can also be increased to ensure a specific SIE value input. The specific method is the same as above. When the amount of waste gas to be treated is small, or the pollutant molecules to be treated are easier to decompose, that is, when the SIE value is low, the central high-voltage electrode or the second high-voltage electrode can be used alone (i.e., reducing P0) or increasing the gas volume (i.e., increasing Q), thereby reducing energy consumption and improving energy utilization.

[0048]

[0049] Wherein, in Formula 2, f is the applied driving power frequency (in Hz), U is the power supply voltage applied to the plasma generator (in V), and I is the current through the plasma generator (in A). In the specific implementation of the present invention, in order to further utilize the existing device to increase power and improve the injected energy, the driving power frequency f operating parameter is mainly fixed during the actual operation process (due to the use of the existing device, the device resistance is a fixed value, so the current I therein is determined by the power supply voltage U). In the specific implementation, in order to meet the needs of different VOCs to be treated, on the basis of utilizing the existing coaxially arranged plasma generating device, in order to meet the degradation needs of VOCs of different concentrations, the injection energy can be increased by increasing the voltage U peak value / amplitude to improve the efficiency of plasma treatment of waste gas; in another specific implementation of the present invention, the driving power frequency can be changed to achieve the effect of affecting the injected energy value; and in another specific implementation of the present invention, when the driving power adopts a pulse power supply, the duty cycle of the power input can be changed to affect the injected energy value.

[0050] In the present invention, the number of the plasma discharge reactors is 2, and the two plasma discharge reactors are connected in series or in parallel. In a specific embodiment of the present invention, the two plasma discharge reactors are connected in series or in parallel. According to the different waste gases to be treated, the two plasma discharge reactors can be the same discharge mode (only along the surface discharge, only dielectric barrier discharge or along the surface-dielectric barrier composite discharge), and the two plasma discharge reactors can also be different discharge modes, for example, one plasma discharge reactor is along the surface discharge, and the other plasma discharge reactor is dielectric barrier discharge; or one plasma discharge reactor is along the surface discharge, and the other plasma discharge reactor is along the surface-dielectric barrier discharge; or one plasma discharge reactor is dielectric barrier discharge, and the other plasma discharge reactor is along the surface-dielectric barrier discharge.

[0051] In the present invention, preferably, the number of the plasma discharge reactors is 3 or more, and the plurality of the plasma discharge reactors are connected in series and / or in parallel. In a specific embodiment of the present invention, three plasma discharge reactors are included (represented by plasma discharge reactor 1, plasma discharge reactor 2 and plasma discharge reactor 3, respectively), and the three 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 sequentially connected in series or in parallel with each other; or, plasma discharge reactor 2 and plasma discharge reactor 3 are connected in parallel and then connected in series with plasma discharge reactor 1. According to the different waste gases to be treated, the three plasma discharge reactors can all have the same discharge mode (only surface discharge, only dielectric barrier discharge or surface-dielectric barrier composite discharge), and the three plasma discharge reactors can also have different discharge modes. Specifically, in the connection mode in which the three plasma discharge reactors are connected in series in sequence or the three plasma discharge reactors are connected in parallel, plasma discharge reactor 1 is surface discharge, and plasma discharge reactor 2 and plasma discharge reactor 3 are dielectric barrier discharge; or plasma discharge reactor 1 is dielectric barrier discharge, and plasma discharge reactor 2 and plasma discharge reactor 3 are surface discharge; or plasma discharge reactor 1 is dielectric barrier discharge, plasma discharge reactor 2 is surface discharge, and plasma discharge reactor 3 is dielectric barrier discharge; or plasma discharge reactor 1 is surface discharge, plasma discharge reactor 2 is dielectric barrier discharge, and plasma discharge reactor 3 is surface discharge. In the connection mode in which both series and parallel connection exist, plasma discharge reactor 1 is surface discharge, and plasma discharge reactor 2 and plasma discharge reactor 3 are dielectric barrier discharge; or plasma discharge reactor 1 is dielectric barrier discharge, and plasma discharge reactor 2 and plasma discharge reactor 3 are surface discharge; or plasma discharge reactor 1 is dielectric barrier discharge, plasma discharge reactor 2 is surface discharge, and plasma discharge reactor 3 is dielectric barrier discharge; or plasma discharge reactor 1 is surface discharge, plasma discharge reactor 2 is dielectric barrier discharge, and plasma discharge reactor 3 is surface discharge. For the connection mode of more than three plasma discharge reactors and their specific discharge modes, a variety of selections and combinations can be made, which will not be repeated here.

[0052] In the present invention, preferably, the second high-voltage electrode 2 is a metal coil.

[0053] In the present invention, preferably, the metal coil of the second high-voltage electrode 2 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 greater than the outer diameter of the central high-voltage electrode 1. Figure 1 As shown, the metal coil of the second high-voltage electrode 2 is arranged around the central high-voltage electrode 1 , and the inner diameter of the metal coil of the second high-voltage electrode 2 is greater than the outer diameter of the central high-voltage electrode 1 .

[0054] There is no particular limitation on the pitch of the metal coil, as long as it can achieve gas discharge to generate plasma. In the present invention, preferably, the pitch of the metal coil is 0.5-15 mm; more preferably, the pitch of the metal coil is 1-10 mm.

[0055] There is no particular limitation on the diameter of the metal coil, as long as it can achieve gas discharge to generate plasma. In the present invention, preferably, the diameter of the metal coil is 0.05-3 mm; more preferably, the diameter of the metal coil is 0.1-2 mm.

[0056] There is no particular limitation on the conductivity of the metal coil, as long as it can affect the intensity of the electric field and the concentration of active particles generated by gas ionization. In the present invention, preferably, at 25° C., the metal coil has a conductivity of 10 5 -10 8 S / m of metal; more preferably, at 25 ° C, the metal coil has a conductivity of 10 7 S / m of metal.

[0057] 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; further preferably, the metal coil is iron, copper or tungsten. In a specific embodiment of the present invention, an iron coil is selected.

[0058] There is no particular limitation on the plasma reaction tube, and it can be any conventional reaction tube with insulation performance in the art. In the present invention, preferably, 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 present invention, the plasma reaction tube is a quartz tube; in another embodiment of the present invention, the plasma reaction tube is a corundum tube.

[0059] There is no particular limitation on the shape of the central high-voltage electrode 1 , and it may be any shape of electrodes conventionally used in the art. In the present invention, preferably, the central high-voltage electrode 1 is tubular or rod-shaped.

[0060] There is no particular limitation on the tubular central high-voltage electrode, and it can be any conventional tube with insulating properties in the art. In the present invention, preferably, the tubular central high-voltage electrode 1 is an insulating medium tube; the insulating medium tube is filled with a conductive metal tube or is filled with conductive metal powder. In a specific embodiment of the present invention, the insulating medium tube is filled with metal powder.

[0061] There is no particular limitation on the insulating medium tube. In the present invention, preferably, the insulating medium tube is a quartz tube, ceramic, corundum or polytetrafluoroethylene tube. In one embodiment of the present invention, the insulating medium tube is a quartz tube; in another embodiment of the present invention, the insulating medium tube is a corundum tube.

[0062] There is no particular limitation on the above-mentioned conductive metal powder. In the present invention, preferably, the conductive metal powder is one or more of iron, copper, magnesium or aluminum. In a specific embodiment of the present invention, iron powder is selected as the metal conductive powder (specifically iron powder) and filled in an insulating medium tube (specifically a quartz tube) as a central high-voltage electrode. Those skilled in the art may also select other metal powders with conductive properties to be filled in an insulating medium tube as a central high-voltage electrode as needed.

[0063] In the present invention, preferably, the central high-voltage electrode 1 is an insulating medium tube, and the insulating medium tube has a conductive metal rod or tube. In another specific embodiment of the present invention, quartz, ceramic, corundum tube or polytetrafluoroethylene can be used as an insulating tube, and a metal rod is embedded in the tube as the central high-voltage electrode; and in another specific embodiment of the present invention, a metal tube is embedded in an insulating tube as the central high-voltage electrode.

[0064] There is no particular limitation on the material of the metal rod or tube embedded in the insulating tube. For example, the material may be a material with an electrical conductivity of 10 at 25°C. 5 -10 8 In one embodiment of the present invention, an iron rod is embedded in a quartz tube and used as a central high voltage electrode.

[0065] There is no particular limitation on the tubular or rod-shaped central high-voltage electrode, and it can be any conventional high-voltage electrode in the art. In the present invention, preferably, at 25° C., the rod-shaped central high-voltage electrode 1 has a conductivity of 10 5 -10 8 S / m of metal; more preferably, at 25 ° C, the rod-shaped central high-voltage electrode 1 has a conductivity of 10 7 S / m of metal. In one embodiment of the present invention, at 25°C, the central high voltage electrode 1 has an electrical conductivity of 10 7 S / m metal.

[0066] There is no particular limitation on the ground electrode, and it may be, for example, a metal mesh or a metal sheet.

[0067] There is no limitation on the working gas in the plasma discharge reactor of the present invention, and it can be fixed air, nitrogen, helium or argon commonly used in the art, and those skilled in the art can also select one or more according to actual needs.

[0068] In a second aspect, the present invention provides a method for treating waste gas, wherein the method adopts the composite plasma discharge device. Specifically, Figure 1 In the device shown, the central high-voltage electrode 1 is located in the plasma reaction tube 4 and is coaxially arranged with the plasma reaction tube 4. The ground electrode 3 is closely 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 and is closely attached to the inner wall of the plasma reaction tube 4. The plasma reaction tube 4 is provided with a gas inlet and a gas outlet. The central high-voltage electrode 1 and the second high-voltage electrode 2 are applied with independent power supply systems, and different driving power supplies (including different voltages and frequencies, etc.) are selected respectively, so that three discharge modes can be realized: (1) when voltage is applied only to the central high-voltage electrode 1, plasma is generated in the form of dielectric barrier discharge, which is suitable for hydrocarbons such as toluene, xylene, and cyclohexane; (2) when voltage is applied only to the second high-voltage electrode 2, plasma is generated in the form of surface discharge, which is suitable for hydrocarbon derivatives such as methanol and formaldehyde; (3) when high voltage is applied to the central high-voltage electrode 1 and the second high-voltage electrode 2 at the same time, plasma is generated in the form of surface discharge and single dielectric barrier discharge coupling, which is suitable for the above two forms (1) and (2) of waste gas molecules that are not easy to degrade, such as benzene, H2S, etc.

[0069] In the present invention, the driving power supply of the central high-voltage electrode 1 and the driving power supply of the second high-voltage electrode 2 are used separately or simultaneously. The difference in the driving power supply means that the driving power supplies of the central high-voltage electrode 1 and the second high-voltage electrode 2 are independent of each other, or the voltage and / or frequency of the two driving power supplies are different; or the voltage may be applied only to the central high-voltage electrode 1, or only to the second high-voltage electrode (2), or to the first high-voltage electrode and the second high-voltage electrode simultaneously. When the above power supplies are used separately, dielectric barrier discharge or surface discharge is formed respectively, and when the two high-voltage electrodes are driven simultaneously, a composite electric field of surface-dielectric barrier discharge is formed. Figure 2 Schematic diagram of the discharge area during surface discharge, dielectric barrier discharge and surface-dielectric barrier discharge in the plasma discharge reactor of the present invention. Figure 2 As shown, when only the driving power source HV1 of the central high voltage electrode 1 is used, the central high voltage electrode forms a dielectric barrier discharge, forming a dielectric barrier discharge electric field, such as Figure 2When only the driving power source HV2 of the second high voltage electrode is used, a surface discharge is formed between the second high voltage electrode and the plasma reaction tube, forming a surface discharge electric field, such as Figure 2 b; when the driving power source HV1 and the driving power source HV2 are used at the same time, two forms of discharge are generated at the same time, namely, the surface-dielectric barrier composite discharge, forming the surface-dielectric barrier discharge composite electric field, as shown in FIG. Figure 2 As shown in c.

[0070] There is no particular limitation on the driving power supply of the central high-voltage electrode or the second high-voltage electrode. In the present invention, preferably, the driving power supply of the central high-voltage electrode 1 or the second high-voltage electrode 2 is a direct current, an alternating current, or an alternating-direct current composite power supply. In a specific embodiment of the present invention, the driving power supply of the central high-voltage electrode 1 or the second high-voltage electrode 2 is an alternating current power supply.

[0071] There is no particular limitation on the AC power supply. In the present invention, preferably, the AC power supply has a frequency of 10 Hz-10 kHz, a voltage peak of 0.1-50 kV, and a voltage waveform of a sine wave, a pulse wave, a square wave, a triangle wave, or a sawtooth wave. In a specific embodiment of the present invention, the AC power supply has a frequency of 7 kHz, a voltage peak of 32 kV, a duty cycle of 0.3, and a sine wave.

[0072] There is no particular limitation on the DC power supply. In the present invention, preferably, the DC power supply has a positive or negative polarity and a voltage amplitude of 0.1-50 kV. In a specific embodiment of the present invention, the DC power supply has a negative polarity and a voltage amplitude of 15 kV.

[0073] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, all materials used can be obtained commercially, and unless otherwise specified, the methods used are conventional methods in the art.

[0074] Example 1

[0075] use Figure 1 In the device shown, a central high-voltage electrode 1 (specifically a stainless steel tube with an outer diameter of 10 mm) is located in a plasma reaction tube 4 (specifically a quartz tube with an inner diameter of 16 mm), and is coaxially arranged with the plasma reaction tube 4. A grounding electrode 3 (specifically a copper sheet with a length of 10 cm) is closely attached to the outer wall of the plasma reaction tube 4. A second high-voltage electrode 2 (specifically an iron coil with a pitch of 2 mm and an outer diameter of 16 mm) is arranged around the central high-voltage electrode 1. The second high-voltage electrode 2 is closely attached to the inner wall of the plasma reaction tube 4. A gas inlet and a gas outlet are provided on the plasma reaction tube 4. A high-voltage AC power supply is applied to the high-voltage electrode 1 and the high-voltage electrode 2, with a frequency of 7 kHz and a voltage of 32 kV.

[0076] The above device was used to treat exhaust gas with a flow rate of 1 L / min. The results are shown in Table 1 below.

[0077] Table 1

[0078] Exhaust gas type Discharge method Removal efficiency 200ppm Toluene Apply voltage only to the central high voltage electrode 1 95.8％ 200ppm benzene Apply voltage only to the central high voltage electrode 1 85.0％ 200ppm formaldehyde Only the voltage is applied to the second high voltage electrode 2 80.3％ 400ppm benzene Apply voltage to high voltage electrodes 1 and 2 at the same time 81.5％

[0079] Example 2

[0080] The same plasma discharge device as in Example 1 is used, except that a high voltage with different parameters is applied only to the central high-voltage electrode 1 .

[0081] The above device was used to treat 300 ppm toluene waste gas at a flow rate of 1 L / min. The results are shown in Table 2 below.

[0082] Table 2

[0083] High voltage parameters 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％ Triangle 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％

[0084] Example 3

[0085] The same plasma discharge device as in Example 1 was used, and high voltage electrodes 1 and 2 were simultaneously supplied with high voltage AC power, sinusoidal wave, frequency of 7kHz, voltage of 34kV, and duty cycle of 0.3. The above device was used to treat waste gas containing benzene with a concentration of 200ppm at different flow rates. The results are shown in Table 3 below.

[0086] Table 3

[0087] Exhaust gas flow Removal efficiency 1L / min 96.2％ 10L / min 94.0％ 15L / min 92.0％

[0088] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A composite plasma discharge device, characterized in that: 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) coaxially arranged with the plasma reaction tube (4), a grounding electrode (3) closely attached to the outer wall of the plasma reaction tube (4), and a second high-voltage electrode (2) closely attached to the inner wall of the plasma reaction tube (4).

2. The composite plasma discharge device according to claim 1, wherein: The number of the plasma discharge reactors is 2, and the two plasma discharge reactors are connected in series or in parallel.

3. The composite plasma discharge device according to claim 1, wherein: The number of the plasma discharge reactors is 3 or more, and the 3 or more plasma discharge reactors are connected in series and / or in parallel.

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

5. The 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).

6. The composite plasma discharge device according to claim 5, wherein: The inner diameter of the metal coil of the second high-voltage electrode (2) is greater than the outer diameter of the central high-voltage electrode (1).

7. The 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.

8. The composite plasma discharge device according to claim 4, wherein: The pitch of the metal coil of the second high-voltage electrode (2) is 1-10 mm.

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

10. The composite plasma discharge device according to claim 4, wherein: The diameter of the metal coil of the second high-voltage electrode (2) is 0.1-2 mm.

11. The composite plasma discharge device according to claim 4, wherein: At 25°C, the second high voltage electrode (2) metal coil has an electrical conductivity of 10 5 -10 8 S / m of metal.

12. The composite plasma discharge device according to claim 4, wherein: The metal is a high temperature resistant conductive metal.

13. The composite plasma discharge device according to any one of claims 1 to 12, wherein: The plasma reaction tube (4) is an insulating medium tube.

14. The composite plasma discharge device according to claim 13, wherein: The insulating medium is quartz, ceramic, corundum or polytetrafluoroethylene.

15. The composite plasma discharge device according to any one of claims 1 to 12, wherein: The central high-voltage electrode (1) is in a tubular or rod shape.

16. The composite plasma discharge device according to claim 15, wherein: The tubular central high-voltage electrode (1) is an insulating medium tube, and the insulating medium tube is filled with conductive metal powder.

17. The composite plasma discharge device according to claim 16, wherein: A conductive metal rod is arranged inside the insulating medium tube.

18. The composite plasma discharge device according to claim 16, wherein: The insulating medium tube is provided with a conductive metal tube.

19. The composite plasma discharge device according to claim 16, wherein: The insulating medium tube is made of quartz, ceramic, corundum or polytetrafluoroethylene.

20. The composite plasma discharge device according to any one of claims 1 to 12, at 25°C, wherein: The central high voltage electrode (1) has an electrical conductivity of 10 5 -10 8 S / m of metal.

21. A method for treating waste gas, characterized in that: The treatment method adopts the composite plasma discharge device described in any one of claims 1-20.

22. The method for treating waste gas according to claim 21, 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).

23. The method for treating waste gas according to claim 22, wherein: The driving power source of the central high-voltage electrode (1) or the second high-voltage electrode (2) is a direct current, alternating current, or an alternating current and direct current composite power source.

24. The method for treating waste gas according to claim 23, wherein: The frequency of the AC power supply is 10 Hz-10 kHz, the voltage peak is 0.1-50 kV, and the voltage waveform is a sine wave, a pulse wave, a square wave, a triangle wave or a sawtooth wave.

25. The method for treating waste gas according to claim 23, wherein: The DC power supply has a positive or negative polarity and a voltage amplitude of 0.1-50 kV.

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