VOCs degradation device based on magnetic field enhanced plasma

Abstract

The VOCs degradation device comprises a power distribution unit and a reaction unit, the power distribution unit is composed of a nanosecond pulse power source and a signal source, the reaction unit comprises a reactor shell, a reaction electrode and a permanent magnet, the reactor shell is composed of a stainless steel shell, and the two ends of the reactor shell are sealed through insulating plates and rubber rings; the reaction electrode is designed to be in a multi-row tip nail type and is composed of an electrode body and electrode needle bodies, an electrode needle body array is embedded in the electrode body, and the permanent magnet is fixedly installed outside the reactor through a 304 stainless steel pipe clamp. The electric energy loss is reduced; the magnetic field of the permanent magnet is used for promoting Larmor motion of free electrons, the ionization process of gas molecules in an ionization area is enhanced, and the degradation efficiency is improved. The device is simple in structure, convenient to install, small in occupied space and good in use value.

Description

Technical Field

[0001] The invention relates to a degradation device, in particular to a VOCs degradation device based on magnetic field enhanced plasma, belonging to the technical field of waste gas treatment. Background Art

[0002] Volatile organic compounds (VOCs) are defined as organic compounds with a boiling point below 250°C at atmospheric pressure. They pose a serious threat to human health and the environment and have attracted widespread attention. The end-of-pipe treatment of VOCs can generally be divided into two types: recovery technology and destruction technology. Recovery technology is usually used for high-concentration or expensive VOCs, including adsorption, absorption, membrane separation, and condensation. For medium and low-concentration VOCs, destruction technology is used, including combustion, photocatalytic degradation, biological methods, and low-temperature plasma technology. The treatment process of the adsorption method is relatively complicated, and the adsorbent needs to be regenerated after saturation, which will cause secondary pollution problems. The absorption range of the absorption method is limited and is not suitable for low-concentration VOCs treatment. The disadvantage of the membrane separation method is that it is highly dependent on membrane technology and membrane materials and has high requirements for membranes. The combustion method has high energy consumption and low safety. The photodegradation method has a long reaction time, low efficiency in light utilization, and the by-products formed easily deactivate the photocatalyst. The equipment of the biological method occupies a large area and has a long operating time, which is not suitable for scenarios that require rapid treatment.

[0003] As a very promising VOCs treatment technology, low-temperature plasma technology has the advantages of wide application range, low environmental requirements, and easy operation and operation of equipment. Plasma is often regarded as the fourth state of matter besides solid, liquid and gas. 99% of the matter in the universe is in the form of plasma, which contains a large number of different particles, such as positive and negative ions, electrons, free radicals, etc. Plasma can be divided into high-temperature plasma and low-temperature plasma according to the difference between electron temperature and ion temperature. When the former is much greater than the latter, it is called low-temperature plasma (NTP). By injecting energy into the reactor to form high-energy electrons, they collide and interact with gas molecules (such as electron excitation, ionization and dissociation) and produce various active substances. Then these active substances react with each other to form new active substances, promote the initiation and propagation of chemical reactions in the system and dissociate VOCs into small molecules, which are then oxidized into final products.

[0004] Existing low-temperature plasma reaction equipment mainly uses dielectric barrier discharge (DBD) to generate NTP, which degrades VOCs by generating electrons under a single electric field of sinusoidal excitation or DC excitation. However, compared with corona discharge (CD), the reactor suitable for dielectric barrier discharge is smaller and is not suitable for large-flow gas treatment applications. The energy and chemical activity of NTP generated by DC excitation or sinusoidal excitation are low, and the probability of collision between electrons and gas molecules under a single electric field is low, resulting in low VOCs degradation efficiency. The above reasons lead to the problem that the plasma reaction equipment on the market has no obvious degradation effect on VOCs and is not suitable for large-flow exhaust gas treatment. Therefore, there is an urgent need for a new solution to solve this technical problem. Summary of the invention

[0005] The present invention is aimed at the technical problems existing in the prior art, and provides a VOCs degradation device based on magnetic field enhanced plasma. The technical solution is cleverly designed and compact in structure. It uses magnetic field assistance and permanent magnets fixed at both ends of the reactor to apply a magnetic field in a certain direction, changing the trajectory of electrons in the reaction area to enhance the collision probability between electrons and VOCs molecules and improve degradation efficiency. Corona discharge is used to be suitable for large-flow gas treatment applications. Nanosecond-level high-voltage pulse power supply excitation is used to generate NTP, a substance with higher energy and stronger chemical activity. The independently designed mace-shaped rare earth tungsten electrode is used to reduce the work function of electrons and improve energy efficiency.

[0006] In order to achieve the above-mentioned purpose, the technical solution of the present invention is as follows: a VOCs degradation device based on magnetic field enhanced plasma, the degradation device comprising a power distribution unit and a reaction unit, the power distribution unit comprising a nanosecond pulse power supply (3) and a signal source (4), the reaction unit comprising a reactor shell (1), a reaction electrode and a permanent magnet, the reactor shell (1) is provided with a reaction electrode (2) and a permanent magnet (5), and is fixed on both sides of the reactor shell (1) using a 304 stainless steel pipe clamp (51), and the pipe clamp bracket can be adjusted up and down to adjust the position of the magnet.

[0007] Among them, the distribution unit is connected to the reaction unit through a wire to provide energy for the reaction.

[0008] The reactor shell (1) is mainly composed of a stainless steel shell (11), and its two ends are sealed by an insulating plate (12) and a rubber ring (13), and its surface is grounded. A round window (14) is installed between the stainless steel shell (11) and the insulating plate (12) to facilitate observation of discharge phenomena. The reaction electrode (2) is designed as a multi-row pointed nail type, consisting of a plurality of electrode needle bodies (21) and an electrode body (22). The electrode needle body (21) is made of rare earth tungsten alloy, and each needle is 25 mm long and 3 mm in diameter. The electrode body (22) is made of stainless steel, with a diameter of 12 mm and a length of 270 mm. The electrode needle body (21) array is embedded in the electrode body (22), and the array method is to position every 90° around the circumference, and the linear array is spaced 30 mm apart, with a total of 6 arrays.

[0009] The nanosecond pulse power supply (3) can output a peak voltage of 15 kV and a rising edge of 50 ns.

[0010] The frequency of the signal source (4) is continuously adjustable within the range of 1-3000Hz, and the pulse width can be adjusted within 0.5-1000μs. The permanent magnet (5) is composed of two magnets of the same size, each of which is mainly composed of neodymium iron boron material, and is symmetrically fixed on both sides of the reactor housing (1) using 304 stainless steel pipe clamps (51), and the pipe clamp bracket can be adjusted up and down to adjust the position of the magnet. The base is made of a customized 30*20*2cm solid paulownia wood board, and the pipe clamp is fixed by drilling screws according to the position relationship requirements or the pipe bracket is rotated to change the magnet arrangement direction. When replacing the magnet, there is no need to remove the pipe clamp, just loosen the pipe clamp screws.

[0011] The reaction electrode (2) is of a mace type and is connected to a nanosecond high-voltage pulse power supply (3) and a signal source (4).

[0012] The electrode needle body (21) mainly comprises yttrium oxide (Y2WO6), lanthanum oxide (La2WO6), cerium oxide (Ce2WO6) and tungsten, wherein tungsten occupies the main part, accounting for 98%.

[0013] Compared with the prior art, the present invention has the following advantages: 1. The scheme utilizes magnetic field to assist the reaction. The electrons assisted by the magnetic field produce Larmor motion, which can effectively increase the electron density and improve the reaction efficiency. The magnet fixing method of the present invention can adjust the angle between the magnetic field and the reactor to obtain a higher degradation efficiency, which has a certain flexibility; 2. The scheme uses nanosecond pulse high-voltage power supply discharge. The NTP generated by nanosecond pulse excitation has higher energy and more chemically active substances. The frequency of the power distribution unit used in the present invention is continuously adjustable within the range of 1-3000Hz, the pulse width can be adjusted within 0.5-1000μs, the peak voltage is 15kV, and the rising edge is 50ns, so that the treatment efficiency of the VOCs waste gas to be treated is effectively guaranteed; 3. The scheme uses self-designed multi-row tip nail-type rare earth tungsten electrodes. The electrode involved in the present invention uses a ternary rare earth tungsten functional composite material. The discharge electrode prepared with the material has excellent electron emission capability and can generate a large number of source electrons with high initial kinetic energy. These source electrons obtain more energy under the action of the electric field and accelerate to collide with other molecules in the flue gas, promote gas discharge, and are beneficial to reduce energy consumption, generate high-density low-temperature plasma, and promote the removal of pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the working structure of the present invention;

[0015] Figure 2 It is a schematic diagram of the reactor structure of the present invention;

[0016] Figure 3 It is a schematic diagram of the electrode structure of the present invention.

[0017] In the figure: 1. reactor shell, 2. reaction electrode, 3. nanosecond pulse power supply, 4. signal source, 5. permanent magnet, 11. stainless steel shell, 12. insulating plate, 13. rubber ring, 14. round window, 15. reactor bracket, 21. electrode needle body, 22. electrode body, 51. stainless steel pipe clamp, 52. magnet bracket. DETAILED DESCRIPTION

[0018] In order to deepen the understanding of the present invention, the present embodiment is described in detail below with reference to the accompanying drawings.

[0019] Example 1: See Figure 1 , Figure 2 ,like Figure 1 The VOCs degradation device based on magnetic field enhanced plasma described in the present invention comprises five parts: a reactor shell 1, a reaction electrode 2, a nanosecond pulse power supply 3, a signal source 4 and a permanent magnet 5;

[0020] The main body of the reactor shell 1 is composed of a stainless steel shell 11, both ends of which are sealed by insulating plates 12 and rubber rings 13, and its surface is grounded; a round window 14 is installed between the stainless steel shell 11 and the insulating plate 12 to facilitate observation of discharge phenomena; the reactor shell 1 is supported by a reactor bracket 15.

[0021] The reaction electrode 2 is placed inside the reactor housing 1 and is designed as a multi-row pointed nail type, consisting of a plurality of electrode needle bodies 21 and an electrode main body 22 , wherein the electrode main body 22 is surrounded by a plurality of electrode needle bodies 21 .

[0022] The nanosecond pulse power supply 3 and the signal source 4 are connected to the reaction electrode 2 through the reactor housing 1 to provide nanosecond pulse high voltage for the reaction.

[0023] The permanent magnets 5 are symmetrically fixed in parallel on both sides of the reactor housing 1 to provide a magnetic field for the reaction. The stainless steel pipe clamps 51 used to fix the magnets are supported by the magnet brackets 52 .

[0024] Specifically, the system consists of a reactor housing 1, a reaction electrode 2, a nanosecond pulse power supply 3, a signal source 4 and a permanent magnet 5. Its working structure is as follows: Figure 1 shown.

[0025] See also Figure 3 ,like Figure 3 The reaction electrode 2 adopts a multi-row pointed nail structure: the electrode body 22 is made of stainless steel, with a diameter of 12 mm and a length of 270 mm. The needle body 21 is made of rare earth tungsten alloy, each needle is 25 mm long and 3 mm in diameter, and the array is embedded in the electrode body. The array is positioned every 90° around the circumference, the linear array is spaced 30 mm apart, and there are 6 arrays in total.

[0026] The purpose of using the above materials and structures is that rare earth tungsten electrodes have excellent electron emission capabilities, which can generate more high-energy electrons in the reactor during the discharge process. These high-energy electrons react with the active substances and benzene molecules together, thereby accelerating their degradation. The multi-row pointed nail-shaped structure is made so that the electric field intensity at the electrode needle body 21 is the highest, which can more easily overcome the binding force of gas molecules and strip the electrons in the gas molecules from atoms or molecules to form free electrons and positive ions.

[0027] The permanent magnet 5 is symmetrically fixed on both sides of the reaction shell 1 using a 304 stainless steel pipe clamp 51 to provide a magnetic field for the reaction, and the magnetic field strengthens the constraint on the electrons in the discharge area. Under the combined action of the magnetic field and the electric field, the electrons perform Larmor motion rotating around the central axis. The Larmor motion not only significantly prolongs the moving path of the electrons in the discharge area, but also greatly increases the residence time of the electrons in the area. With the extension of the electron movement path and the increase of the residence time, the electron density in the discharge area is improved. At the same time, under the action of the electric field of the high-voltage nanosecond pulse power supply, an electron avalanche is generated in the discharge area, and the positive ions generated by ionization remain behind the electron avalanche area to continue to attract electrons, forming a secondary electron avalanche on the path, and the secondary electron avalanche further develops the ionization, produces more positive ions, and under the action of the magnetic field, the electron avalanche is enhanced, and more electrons are attracted to participate in elastic collision, excitation and ionization, and the concentration of active substances in the reaction area increases accordingly. The above-mentioned active substances are used to achieve the purpose of degrading VOCs.

[0028] Performance Testing:

[0029] The system of the embodiment of the present invention can set different discharge parameters (discharge voltage, discharge frequency, rising edge, etc.) and magnetic field parameters (magnet spacing, angle of magnet arrangement direction, etc.) according to different concentrations of VOCs, give full play to the Larmor motion and electron avalanche effect of electrons, and improve degradation efficiency.

[0030] According to the parameter values ​​in Table 1 below, eight groups of devices were set up and their degradation efficiencies were tested respectively. It can be seen that both the power supply parameters and the magnet parameters have an impact on the degradation efficiency of toluene.

[0031] Table 1: Performance test of reaction system under different high voltage pulse power supply parameters and permanent magnet parameters

[0032]

[0033]

[0034] In a preferred embodiment, the nanosecond pulse power supply 3 and the signal source 4 are set according to the following parameters: the pulse discharge frequency is 3kHz, the pulse width is 500ns, and the discharge voltage is 14kV;

[0035] In a preferred embodiment, the permanent magnet 5 is composed of two pieces of neodymium iron boron material, fixed in parallel between the reactor shell 1, and the magnet spacing is 81 mm.

[0036] It should be noted that the above embodiments are not intended to limit the protection scope of the present invention, and equivalent changes or substitutions made on the basis of the above technical solutions all fall within the protection scope of the claims of the present invention.

Claims

1. A VOCs degradation device based on magnetic field enhanced plasma, characterized in that: The degradation device comprises a power distribution unit and a reaction unit, wherein the power distribution unit is composed of a nanosecond pulse power supply (3) and a signal source (4), and the reaction unit comprises a reactor shell (1), a reaction electrode (2) and a permanent magnet (5), wherein the reaction electrode (2) is arranged in the reactor shell (1), and the permanent magnet (5) is fixed on both sides of the reactor shell (1), and the power distribution unit is connected to the reaction unit via a wire to provide energy for the reaction.

2. The VOCs degradation device based on magnetic field enhanced plasma according to claim 1 is characterized in that: The reactor shell (1) is mainly composed of a stainless steel shell (11), the two ends of which are sealed by an insulating plate (12) and a rubber ring (13), and the surface is grounded. A round window (14) is provided between the stainless steel shell (11) and the insulating plate (12) to facilitate observation of discharge phenomena.

3. The VOCs degradation device based on magnetic field enhanced plasma according to claim 2 is characterized in that: The reaction electrode (2) is designed as a multi-row pointed nail type, consisting of a plurality of electrode needle bodies (21) and an electrode main body (22), wherein the electrode needle body (21) is made of a rare earth tungsten alloy, and the electrode main body (22) is made of stainless steel. The electrode needle body (21) array is embedded in the electrode main body (22), and the array is positioned every 90° around the circumference, and the linear array is spaced 30 mm apart, with a total of 6 arrays.

4. The VOCs degradation device based on magnetic field enhanced plasma according to claim 1, characterized in that: The nanosecond pulse power supply (3) can output a peak voltage of 15 kV and a rising edge of 50 ns.

5. The VOCs degradation device based on magnetic field enhanced plasma according to claim 1, characterized in that: The frequency of the signal source (4) can be continuously adjusted within the range of 1-3000 Hz, and the pulse width can be adjusted within the range of 0.5-1000 μs.

6. The VOCs degradation device based on magnetic field enhanced plasma according to claim 2, characterized in that: The permanent magnet (5) is composed of two magnets of the same size, each of which is mainly composed of neodymium iron boron material. The two magnets are symmetrically fixed on both sides of the reactor shell (1) using 304 stainless steel pipe clamps (51), and the pipe clamp bracket can be adjusted up and down to adjust the position of the magnet. The base is made of solid Paulownia wood board, and the pipe clamp is fixed by drilling screws according to the position relationship requirements or the pipe bracket is rotated to change the magnet arrangement direction. When replacing the magnet, there is no need to remove the pipe clamp, and only the pipe clamp screws need to be loosened.

7. The VOCs degradation device based on magnetic field enhanced plasma according to claim 3, characterized in that: The reaction electrode (2) is of a mace shape and is connected to a nanosecond high-voltage pulse power supply (3) and a signal source (4).

8. The VOCs degradation device based on magnetic field enhanced plasma according to claim 3, characterized in that: The electrode needle body (21) mainly comprises yttrium oxide (Y2WO6), lanthanum oxide (La2WO6), cerium oxide (Ce2WO6) and tungsten, wherein tungsten occupies the main part, accounting for 98%.

9. The VOCs degradation device based on magnetic field enhanced plasma according to claim 2, characterized in that: The reactor shell (1) is supported by a reactor support (15), and the permanent magnet (5) and the stainless steel pipe clamp (51) are supported by a magnet support (52).

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