System for degrading dichloromethane by coupling low-temperature plasma with ultraviolet-bubble tower

Abstract

The utility model discloses a system for degrading dichloromethane by coupling low-temperature plasma with an ultraviolet-bubble tower, and belongs to the technical field of chlorine-containing volatile organic compound treatment. Comprising a low-temperature plasma device and an ultraviolet-bubble tower device, a first gas outlet of the low-temperature plasma device is communicated with a second gas inlet of the ultraviolet-bubble tower device; a first air inlet and a first air outlet of the low-temperature plasma device are formed in the same side; the ultraviolet-bubbling tower device comprises a plurality of ultraviolet lamps, a plurality of layers of bubbling areas arranged along the height direction, and a solution tank arranged at the bottom; a second air outlet is formed in the top of the ultraviolet-bubble tower device. The solubility of DCM in a liquid phase is increased after low-temperature plasma treatment, the effective residence time of DCM in a system is prolonged through an ultraviolet-bubble tower, by-products are efficiently retained in the liquid phase, organic matter can be deeply degraded, and environmental pollution is avoided. In addition, the system only takes water as a medium, and the problems of catalyst deactivation, treatment and the like are not involved.

Description

Technical Field

[0001] The utility model belongs to the technical field of treating chlorine-containing volatile organic compounds, and particularly relates to a system for degrading dichloromethane by using a low-temperature plasma coupled ultraviolet-bubble tower. Background Art

[0002] With the rapid development of the chemical industry, chlorinated volatile organic compounds (VOCs) have become a key focus of air pollution control due to their widespread use. It is estimated that nearly 80% of dichloromethane produced globally is released into the atmosphere. Dichloromethane (DCM) readily produces pollutants such as phosgene and carbon monoxide when exposed to ultraviolet light, posing significant risks to the ecological environment and human health. Furthermore, inhalation of liquid and highly concentrated DCM vapor through the skin, mucous membranes, and nasal passages can cause irritation to the human body, damage the nervous system, and, in severe cases, liver and kidney damage.

[0003] Low-temperature plasma (NTP) can generate high-energy electrons and reactive free radicals that participate in the excitation and oxidation of pollutants. It is an emerging method for treating low-concentration volatile organic compounds (VOCs), but it also faces the problem of byproduct ozone emissions. Therefore, in current industrial production practice, it is necessary to combine two or more processes according to different process characteristics. Coupling NTP technology with other processes has gradually become a research hotspot. Photocatalytic oxidation is an advanced oxidation process that has been widely used in recent years to treat insoluble and difficult-to-biodegrade gases. Studies have used vacuum ultraviolet technology to degrade dichloromethane waste gas and found that the strong oxidizing species generated during the photolysis process, such as hydroxyl radicals and ozone, play a significant role in dichloromethane degradation. By introducing ultraviolet light into the liquid phase, a series of free radical reactions under UV illumination occur, producing large amounts of ·OH, which degrades organic pollutants. However, using photolysis alone as a waste gas purification process has technical drawbacks. Its biggest limitation is that ultraviolet light cannot completely degrade pollutants.

[0004] Due to the technical problems that the existing NTP technology produces ozone as a byproduct when treating DCM, and ultraviolet rays cannot completely degrade pollutants, there is an urgent need to find an economical and environmentally friendly technology to degrade low-concentration DCM and completely oxidize the residual organic matter in the water. Utility Model Content

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a system for degrading dichloromethane by coupling low-temperature plasma with ultraviolet light and bubbling tower, so as to solve the technical problems that ozone is produced as a byproduct when treating dichloromethane with low-temperature plasma technology, and that ultraviolet light cannot completely degrade pollutants.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] The utility model discloses a system for degrading dichloromethane by coupling a low-temperature plasma with an ultraviolet-bubble tower. The system comprises a low-temperature plasma device and an ultraviolet-bubble tower device. The system comprises a first air outlet of the low-temperature plasma device and a second air inlet of the ultraviolet-bubble tower device. The first air inlet and the first air outlet of the low-temperature plasma device are arranged on the same side. The ultraviolet-bubble tower device comprises a plurality of ultraviolet lamps, a plurality of bubbling zones arranged in a height direction, and a solution pool arranged at the bottom. The second air outlet is provided at the top of the ultraviolet-bubble tower device.

[0008] Preferably, the low-temperature plasma device includes a high-voltage electrode, an insulating medium and a ground electrode arranged in parallel.

[0009] Further preferably, the high-voltage electrode and the grounding electrode are equal in size; the high-voltage electrode and the grounding electrode are both made of stainless steel; the high-voltage electrode and the grounding electrode are both hollow mesh structures, with square meshes, a side length of 20 to 30 mm, and a thickness of 1 to 3 mm.

[0010] Further preferably, the insulating medium is made of ceramic material; the thickness is 1 to 3 mm; the distance between the high-voltage electrode and the insulating medium is equal to the distance between the insulating medium and the grounding electrode, both being 8 to 12 mm.

[0011] Further preferably, the low-temperature plasma device also includes a shell; the high-voltage electrode, the insulating medium and the grounding electrode are installed in the shell; a first air inlet and a first air outlet are provided on the shell; the first air inlet is arranged between the high-voltage electrode and the insulating medium; and the first air outlet is arranged between the insulating medium and the grounding electrode.

[0012] Preferably, a demister is provided between the ultraviolet lamp and the bubbling zone; the demister is a folded plate structure; the demister is 500 to 1000 mm away from the second air outlet; and the spacing between any two bubbling zones is 1100 to 1500 mm.

[0013] Preferably, the bubbling zone includes an overflow weir located on the side and a sieve plate located at the bottom and connected to the overflow weir; the sieve plate is provided with a plurality of evenly distributed air holes.

[0014] Further preferably, the ultraviolet lamp is installed on the upper part of the ultraviolet-bubble tower device and is fixed on the sieve plate.

[0015] Preferably, circulation pumps are provided on both sides of the bottom of the UV-bubble column device.

[0016] Further preferably, the outlet of the solution pool is connected to the inlet of the circulation pump through a liquid delivery pipeline, and the outlet of the circulation pump is connected to the bubbling area through a liquid delivery pipeline.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The utility model discloses a low-temperature plasma coupled ultraviolet-bubble tower system for degrading dichloromethane, comprising a low-temperature plasma device and an ultraviolet-bubble tower device. A first gas outlet of the low-temperature plasma device is connected to a second gas inlet of the ultraviolet-bubble tower device. Gas treated by the low-temperature plasma device can directly and unimpededly enter the ultraviolet-bubble tower device for further degradation treatment, thereby reducing gas loss during transmission and improving overall treatment efficiency. The first gas inlet and the first gas outlet of the low-temperature plasma device are arranged on the same side, which increases the residence time of the gas in the low-temperature plasma device and facilitates efficient gas treatment. The UV-bubble column apparatus comprises several UV lamps, several layers of bubbling zones arranged along its height, and a solution pool at its base. The UV lamps provide the apparatus with photocatalytic degradation capabilities, complementing the low-temperature plasma treatment and further improving the degradation efficiency of DCM. The multiple bubbling zones increase the gas-liquid contact area, allowing DCM in the gas to more fully contact and react with active components in the solution, enhancing mass transfer efficiency and degradation effectiveness. The solution pool at the base provides the necessary liquid for the bubbling zones and also collects and processes DCM and other harmful substances removed from the gas. A second gas outlet is located at the top of the UV-bubble column apparatus, ensuring smooth discharge of the treated gas, completing the entire treatment process. After the reaction is complete, VOC-free air is introduced, allowing the refractory organic pollutants in the liquid phase to be mineralized through the combined action of ozone and UV light. The utility model discloses a low-temperature plasma coupled ultraviolet-bubble tower system for degrading dichloromethane. The system utilizes high-energy electrons, active oxygen species (·OH, ·O, ·N), ozone, and other substances generated by the flat dielectric barrier discharge excitation of the low-temperature plasma device to perform primary degradation of DCM. This increases the solubility of DCM in the liquid phase, increases the mass transfer efficiency between DCM and the active components in the liquid phase, and increases the residence time of DCM in the ultraviolet-bubble tower device, thereby improving the removal efficiency and mineralization rate of DCM. The ultraviolet-bubble tower device utilizes the ultraviolet light decomposition byproduct O3 to produce ·OH, which deeply oxidizes the incompletely mineralized dichloromethane for secondary degradation. The ultraviolet-bubble tower device extends the effective residence time of DCM in the system, provides conditions for the deep degradation of organic matter, and efficiently retains the byproducts generated in the previous step in the liquid phase, avoiding pollution to the environment. Under the irradiation of ultraviolet light, the byproduct O3 generated by the low-temperature plasma acts as an oxidant, and the aerosol particles generated by the discharge are retained in the water, reducing the threat to the atmospheric environment. The combination of the high-energy electrons and active substance generation capabilities of low-temperature plasma and the photocatalytic effect of ultraviolet light makes the degradation efficiency of DCM higher. No catalyst is needed. After completion, the flow of air without DCM is stopped. Under the action of ozone + ultraviolet light, the residual organic matter in the water can be completely oxidized, and there is no problem of wastewater discharge and treatment.By introducing DCM into a low-temperature plasma-coupled UV-bubble tower system for dichloromethane degradation, it can be fully converted into CO2 and H2O, achieving efficient degradation of DCM. H2O is used only as a medium, and there are no issues such as catalyst deactivation and treatment. This system has the advantages of compact structure, high treatment efficiency, and environmental friendliness.

[0019] Furthermore, the low-temperature plasma device includes a high-voltage electrode, an insulating medium and a grounding electrode arranged in parallel in sequence; the stability of the electric field and the discharge efficiency are ensured, the degradation effect of dichloromethane is improved, and the structure is simple.

[0020] Furthermore, the high-voltage electrode and the ground electrode are equal in size; both the high-voltage electrode and the ground electrode are made of stainless steel; both the high-voltage electrode and the ground electrode are hollow mesh structures, with square meshes, a side length of 20 to 30 mm, and a thickness of 1 to 3 mm; the discharge area is increased, the discharge uniformity and energy utilization are improved, and it is conducive to generating more active species to degrade dichloromethane.

[0021] Furthermore, the insulating medium is made of ceramic material with a thickness of 1 to 3 mm. The distance between the high-voltage electrode and the insulating medium is equal to the distance between the insulating medium and the grounding electrode, both of which are 8 to 12 mm. This ensures the stability and safety of the electric field while also providing good insulation performance.

[0022] Furthermore, the low-temperature plasma device also includes a shell; the high-voltage electrode, the insulating medium and the grounding electrode are installed in the shell; the shell is provided with a first air inlet and a first air outlet; the first air inlet is arranged between the high-voltage electrode and the insulating medium; the first air outlet is arranged between the insulating medium and the grounding electrode, ensuring smooth flow of gas, increasing the residence time of the gas, and improving degradation efficiency.

[0023] Furthermore, a demister is positioned between the UV lamp and the bubbling zone. The demister is a folded plate structure used to separate liquid droplets carried by the DCM. After the purified DCM flows through the demister, the liquid droplets carried by it are removed. The small droplets separated from the airflow gradually condense into larger droplets, which then slide down the demister blades into the solution pool. The demister is located 500 to 1000 mm from the second gas outlet to remove small droplets carried by the gas. The spacing between the bubbling zones is 1100 to 1500 mm. This spacing ensures that the airflow and liquid are fully mixed, resulting in a more uniform airflow distribution within the reactor.

[0024] Furthermore, the bubbling zone includes an overflow weir located on the side and a sieve plate located at the bottom and connected to the overflow weir; the sieve plate is provided with a number of evenly distributed air holes for DCM to move upward from the bottom of the tower, so that the gas can be captured by the droplets during the upward movement, thereby increasing the residence time of the gas in the system and improving the degradation efficiency.

[0025] Furthermore, the UV lamp is installed on the upper part of the UV-bubble column device and is fixed on the sieve plate to ensure that the UV light can fully irradiate the bubbling area and improve the efficiency of UV photocatalytic degradation.

[0026] Furthermore, circulation pumps are installed on both sides of the bottom of the UV-bubble column apparatus. The outlet of the solution pool is connected to the inlet of the circulation pump via a liquid delivery pipe, and the outlet of the circulation pump is connected to the bubbling zone via a liquid delivery pipe. This achieves a circulating flow of the solution, increases the gas-liquid contact area and mass transfer efficiency, and facilitates the degradation of dichloromethane and the absorption of byproducts. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the low-temperature plasma structure of the utility model;

[0028] Figure 2 This is a schematic diagram of the structure of the UV-bubble tower of the utility model;

[0029] Figure 3 Schematic diagram of the high voltage electrode and ground electrode of the low temperature plasma discharge device of the present invention;

[0030] Figure 4 This is a schematic diagram of the structure of the demister of the present utility model;

[0031] Figure 5 This is a schematic diagram of the screen plate structure of the present utility model;

[0032] Figure 6 This is a schematic diagram of the overflow weir structure of the utility model;

[0033] Figure 7 This is a schematic diagram of the system for degrading dichloromethane using a low-temperature plasma coupled UV-bubble tower according to the present invention.

[0034] Among them: 1-UV lamp; 2-demister; 3-overflow weir; 4-air hole; 5-solution pool; 6-circulation pump; 7-second air inlet; 8-second air outlet; 9-sieve plate; 10-housing; 11-high-voltage electrode; 12-insulating medium; 13-ground electrode; 14-first air inlet; 15-first air outlet. DETAILED DESCRIPTION

[0035] In order to help those skilled in the art better understand the present invention, the following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0036] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0037] The present invention is described in further detail below with reference to the accompanying drawings:

[0038] See also Figure 1 This is a schematic diagram of the low-temperature plasma structure of the present invention. As can be seen from the figure, the dielectric barrier discharge flat-plate reactor adopts a plate-type structure. It consists of a housing 10, a high-voltage electrode 11, an insulating dielectric 12, and a grounding electrode 13. The high-voltage electrode 11, insulating dielectric 12, and grounding electrode 13 are mounted within the housing 10. The housing 10 is provided with a first air inlet 14 and a first air outlet 15. The first air inlet 14 is positioned between the high-voltage electrode 11 and the insulating dielectric 12, while the first air outlet 15 is positioned between the insulating dielectric 12 and the grounding electrode 13. The high-voltage electrode 11 and the grounding electrode 13 are of equal size, each measuring 900 mm by 500 mm. During operation, the output voltage is set to 15 to 30 kV. The dimensions of the high-voltage electrode 11 and the grounding electrode 13 can also be adjusted according to specific circumstances.

[0039] Figure 2This is a schematic diagram of the UV-bubble tower structure of the present invention. As can be seen from the figure, a UV lamp 1 is fixed to a sieve plate 9 and installed at the top of the UV-bubble tower. A demister 2 is located between the UV lamp 1 and the bubbling zone. A second gas outlet 8 is provided at the top of the UV-bubble tower. After degrading DCM, it is defogged by the demister 2 and discharged directly into the atmosphere through the second gas outlet 8 at the top of the UV-bubble tower. A solution reservoir 5 is located at the bottom. The wavelength of the UV lamp 1 is 185-254 nm. The UV-bubble tower is equipped with four UV lamps 1 and three bubbling zones. From top to bottom, the UV-bubble tower is equipped with the second gas outlet 8, UV lamp 1, demister 2, bubbling zone, air inlet 7, solution reservoir 5, and circulation pump 6. The bubbling zone consists of an overflow weir 3, a sieve plate 9, and the solution on the sieve plate 9. The sieve plate 9 is provided with air holes 4. The spacing between the two bubbling zones is 1100 to 1500 mm. The provision of bubbling zones can, on the one hand, increase the gas-liquid contact area and improve the ability to capture DCM, and on the other hand, prolong the reaction time and thus improve the degradation ability of DCM. The spacing between the bubbling zones is used to fully mix the airflow and liquid, making the airflow distribution in the reactor more uniform.

[0040] Figure 3 This is a schematic diagram of the high-voltage electrode and grounding electrode of the low-temperature plasma discharge device of the present invention. As can be seen from the figure, the high-voltage electrode 11 and the grounding electrode 13 are made of stainless steel and both have a hollow mesh structure, consisting of a rectangular stainless steel frame and stainless steel wires interwoven within the stainless steel frame. The mesh is a square mesh with a side length of 25mm. The electrode thickness is about 2mm. The insulating medium 12 is made of ceramic material with a thickness of 2mm. The distance between the high-voltage electrode 11 and the insulating medium 12 and the distance between the insulating medium 12 and the grounding electrode 13 are both 10mm. The power supply is an AC power supply with a voltage of 20kV, a frequency of 5kHz, and an airflow velocity of 500m 3 / h.

[0041] Figure 4 The following is a schematic diagram of the demister structure of the present invention. As can be seen, the lower end of the folded plate demister 2 is the air inlet 7, and the upper end is the air outlet 8. The demister 2 is used to separate liquid droplets carried by DCM. After the purified DCM flows through the demister 2, the liquid droplets carried by it are removed. The small droplets separated from the airflow gradually agglomerate into larger droplets, which then slide down the demister blades 2 and fall into the solution pool 5. The demister 2 is located 500-1000 mm from the second air outlet 8 to remove small droplets carried by the gas.

[0042] Figure 5This is a schematic diagram of the sieve plate structure of the present invention. As can be seen from the figure, the sieve plate 9 is evenly provided with multiple air holes 4 for DCM to move upward from the bottom of the tower. The number of air holes 4 can be set according to the liquid-gas ratio and the specific amount of gas to be processed. The air holes 4 on the sieve plate 9 are evenly arranged.

[0043] Figure 6 This is a schematic diagram of the overflow weir structure of the utility model; it can be seen from the figure that the design and position of the overflow weir 3 are crucial to the efficiency and stability of the gas-liquid mass transfer exchange in the tower. The main function is to transport the DCM from the circulation pump 6 to the sieve plate 9 through the pipeline and mix it with the DCM rising through the pores. When the liquid accumulates to a certain extent, the liquid is evenly overflowed from the overflow weir and flows into the solution pool 5. A solution pool 5 is set at the bottom of the UV-bubble tower device, and the outlet of the solution pool 5 is connected to the inlet of the circulation pump 6 through a liquid delivery pipeline, and the outlet of the circulation pump 6 is connected to the three bubbling areas through a liquid delivery pipeline.

[0044] Figure 7 This is a schematic diagram of the low-temperature plasma-coupled UV-bubble column system for dichloromethane degradation according to the present invention. As can be seen from the figure, it includes a low-temperature plasma device and a UV-bubble column device connected in sequence, with the first gas outlet 15 of the low-temperature plasma device communicating with the second gas inlet 7 of the UV-bubble column device. If the UV-bubble column is connected in series with an NTP and then used to degrade DCM, the water solubility of DCM after low-temperature plasma treatment is increased. UV light can utilize the byproduct O3 produced by the NTP degradation of DCM as an oxidant to produce a large amount of ·OH (redox potential 2.8 mV), not only utilizing the byproduct but also deeply oxidizing the DCM and improving its treatment efficiency.

[0045] Example 1

[0046] A low-temperature plasma-coupled UV-bubble column system for degrading dichloromethane (DCM) comprises two components: a low-temperature plasma device and a UV-bubble column. The low-temperature plasma device's first air outlet 15 is connected to the UV-bubble column's second air inlet 7; the low-temperature plasma device's first air inlet 14 and first air outlet 15 are located on the same side. The UV-bubble column comprises four UV lamps 1, three bubbling zones arranged along its height, and a solution reservoir 5 at its base. A second air outlet 8 is located at the top of the UV-bubble column. Combining the high-energy electron and active substance generation capabilities of the low-temperature plasma with the photocatalytic effect of UV light, the degradation efficiency of DCM is enhanced, eliminating the need for catalysts. Upon completion, the introduction of DCM-free air is stopped, and the ozone and UV light combine to completely oxidize any residual organic matter in the water, eliminating wastewater discharge and disposal issues.

[0047] Example 2

[0048] A low-temperature plasma-coupled UV-bubble column system for dichloromethane degradation comprises two components: a low-temperature plasma device and a UV-bubble column. The low-temperature plasma device's first gas outlet 15 is connected to the UV-bubble column device's second gas inlet 7; the low-temperature plasma device's first gas inlet 14 and first gas outlet 15 are located on the same side. The UV-bubble column device comprises four UV lamps 1, three bubbling zones arranged along its height, and a solution reservoir 5 at its base. A second gas outlet 8 is located at the top of the UV-bubble column device. The low-temperature plasma device comprises a high-voltage electrode 11, an insulating dielectric 12, and a grounding electrode 13 arranged in parallel. This ensures electric field stability and discharge efficiency, improving dichloromethane degradation efficiency while maintaining a simple structure. The high-voltage electrode 11 and the ground electrode 13 are equal in size and made of stainless steel. Both electrodes have a hollow mesh structure with square meshes, 20 mm on a side, and 1 mm thick. This increases the discharge area, improves discharge uniformity and energy efficiency, and facilitates the generation of more active species for dichloromethane degradation. The insulating medium 12 is made of ceramic and is 1 mm thick. The distance between the high-voltage electrode 11 and the insulating medium 12 is equal to the distance between the insulating medium 12 and the ground electrode 13, both being 8 mm. This ensures electric field stability and safety while also providing excellent insulation performance. The low-temperature plasma device also includes a housing 10; a high-voltage electrode 11, an insulating medium 12, and a grounding electrode 13 are mounted within the housing 10; a first gas inlet 14 and a first gas outlet 15 are defined in the housing 10; the first gas inlet 14 is positioned between the high-voltage electrode 11 and the insulating medium 12; and the first gas outlet 15 is positioned between the insulating medium 12 and the grounding electrode 13. This ensures smooth gas flow, increases gas residence time, and improves degradation efficiency. By introducing DCM into the low-temperature plasma-coupled UV-bubble column system for dichloromethane degradation, it is fully converted into CO2 and H2O, achieving efficient DCM degradation. This system uses H2O as a medium, avoiding issues such as catalyst deactivation and disposal. The system has the advantages of a compact structure, high treatment efficiency, and environmental friendliness.

[0049] Example 3

[0050] A low-temperature plasma-coupled UV-bubble column system for dichloromethane degradation comprises two components: a low-temperature plasma device and a UV-bubble column device. The low-temperature plasma device's first gas outlet 15 is connected to the UV-bubble column device's second gas inlet 7; the low-temperature plasma device's first gas inlet 14 and first gas outlet 15 are located on the same side. The UV-bubble column device comprises five UV lamps 1, four bubbling zones arranged along its height, and a solution reservoir 5 at its bottom. A second gas outlet 8 is located at the top of the UV-bubble column device. The low-temperature plasma device comprises a high-voltage electrode 11, an insulating medium 12, and a grounding electrode 13, arranged in parallel. The high-voltage electrode 11 and the grounding electrode 13 are of equal size and made of stainless steel. Both electrodes have a hollow mesh structure with square meshes, 30 mm sides, and a thickness of 3 mm. The insulating medium 12 is made of ceramic and has a thickness of 3 mm. The distance between the high-voltage electrode 11 and the insulating medium 12 is equal to the distance between the insulating medium 12 and the ground electrode 13, both being 12 mm. The low-temperature plasma device also includes a housing 10; the high-voltage electrode 11, the insulating medium 12, and the ground electrode 13 are mounted within the housing 10. The housing 10 is provided with a first air inlet 14 and a first air outlet 15; the first air inlet 14 is located between the high-voltage electrode 11 and the insulating medium 12; and the first air outlet 15 is located between the insulating medium 12 and the ground electrode 13. A demister 2 is located between the UV lamp 1 and the bubbling zone. The demister 2 is a folded plate structure that separates liquid droplets carried by the DCM. After the purified DCM passes through the demister 2, the liquid droplets carried along with it are removed. The small droplets separated from the airflow gradually coalesce into larger droplets, which then slide down the demister 2 blades into the solution pool. The demister 2 is located 8500 mm from the second gas outlet, and the spacing between the bubbling zones is 1100 mm. This ensures thorough mixing of the airflow and liquid, resulting in more uniform airflow distribution within the reactor. The bubbling zone includes a lateral overflow weir 3 and a sieve plate 9 at the bottom connected to the overflow weir 3. The sieve plate 9 is equipped with 56 evenly spaced air holes 4. This allows the gas to be captured by the droplets during its upward movement, increasing the gas's residence time in the system and improving degradation efficiency. The UV lamp 1 is mounted on the upper portion of the UV-bubbling column and is fixed through the sieve plate 9. This ensures that UV light can fully reach the bubbling zone, improving the efficiency of UV-catalytic degradation. Circulation pumps 6 are installed on both sides of the bottom of the UV-bubbling tower apparatus. The outlet of the solution reservoir 5 is connected to the inlet of the circulation pump 6 via a liquid delivery pipe, and the outlet of the circulation pump 6 is connected to the bubbling zone via a liquid delivery pipe. This achieves a circulating flow of the solution, increases the gas-liquid contact area and mass transfer efficiency, and facilitates the degradation of dichloromethane and the absorption of byproducts.

[0051] Example 4

[0052] A low-temperature plasma-coupled UV-bubble column system for degrading dichloromethane comprises two components: a low-temperature plasma device and a UV-bubble column device. The low-temperature plasma device's first gas outlet 15 is connected to the UV-bubble column device's second gas inlet 7; the low-temperature plasma device's first gas inlet 14 and first gas outlet 15 are located on the same side. The UV-bubble column device comprises four UV lamps 1, three bubbling zones arranged along its height, and a solution reservoir 5 at its bottom. A second gas outlet 8 is located at the top of the UV-bubble column device. The low-temperature plasma device comprises a high-voltage electrode 11, an insulating medium 12, and a grounding electrode 13, arranged in parallel. The high-voltage and grounding electrodes 11 and 13 are of equal size and are both made of stainless steel. Both electrodes 11 and 13 have a hollow mesh structure with square meshes, 25 mm on each side, and 2 mm thick. The insulating medium 12 is made of ceramic material and has a thickness of 2 mm. The distance between the high-voltage electrode 11 and the insulating medium 12 is equal to the distance between the insulating medium 12 and the ground electrode 13, both being 10 mm. The low-temperature plasma device also includes a housing 10; the high-voltage electrode 11, the insulating medium 12, and the ground electrode 13 are mounted within the housing 10; the housing 10 is provided with a first air inlet 14 and a first air outlet 15; the first air inlet 14 is located between the high-voltage electrode 11 and the insulating medium 12; and the first air outlet 15 is located between the insulating medium 12 and the ground electrode 13. A demister 2 is provided between the UV lamp 1 and the bubbling zone; the demister 2 is a folded plate structure; the demister 2 is 1000 mm from the second air outlet; and the spacing between two bubbling zones is 1500 mm. The bubbling zone includes an overflow weir 3 located on the side and a sieve plate 9 connected to the overflow weir 3 at the bottom; the sieve plate 9 is provided with 56 evenly distributed air holes 4. UV lamp 1 is mounted on the top of the UV-bubble column apparatus and is fixed to sieve plate 9. Circulation pumps 6 are provided on both sides of the bottom of the UV-bubble column apparatus. The outlet of solution reservoir 5 is connected to the inlet of circulation pump 6 via a liquid delivery pipe, and the outlet of circulation pump 6 is connected to the bubbling zone via a liquid delivery pipe.

[0053] The specific process of degrading dichloromethane using a low-temperature plasma coupled ultraviolet-bubble tower degrading dichloromethane system disclosed in the utility model includes:

[0054] 1) DCM is first introduced into a flat-plate dielectric barrier discharge reactor for primary degradation, and then the undegraded DCM and the by-product O3 are introduced into a UV-bubble column for further reaction;

[0055] 2) DCM enters the UV-bubble column from the air inlet 7 and moves upward through the air holes 4 on the sieve plate 9. It is gradually captured by the droplets on the sieve plate 9 transported by the circulation pump 6 and then directly oxidized by O3 or indirectly oxidized by the hydroxyl radicals generated by the decomposition of O3;

[0056] 3) The circulating pump 6 sends the aqueous solution in the tank to the top of the overflow weir in front of the sieve plate 9, and then overflows from the front end of the overflow weir, captures the gas, and then returns to the solution tank 5; the air flow passes through the pores 4 at the bottom of the overflow weir through the liquid layer in the form of bubbles, and dichloromethane dissolves in the liquid phase and reacts. The stirring effect of the bubbles can fully mix the liquid phase.

[0057] 4) The folded plate demister 2 is fixed at the top of the UV-bubble tower to separate the gas and liquid of the purified DCM. Its basic principle is that the droplets in the airflow flow in a tortuous manner in the baffles, continuously collide with the wall and condense into large droplets. Then, under the action of gravity, they slide down along the blades of the demister 2 to the solution pool 5, thereby removing the droplets carried by the airflow.

[0058] 5) The UV lamp 1 is fixed on the sieve plate 9 and installed on the upper part of the UV-bubble tower;

[0059] 6) After the reaction is completed, air is continued to be introduced, and the undegraded organic matter in the liquid phase is further oxidized by using ozone + ultraviolet light.

[0060] The utility model discloses a low-temperature plasma coupled ultraviolet-bubble tower system for degrading dichloromethane. The working principle includes:

[0061] 1) DCM first enters a low-temperature plasma reactor for primary degradation. During the high-voltage discharge process, the high-energy electrons generated react with nitrogen, oxygen, and water vapor in the air, generating reactive species such as hydroxyl radicals, excited gas molecules, reactive oxygen species, and O₃. These reactive species further decompose DCM into small organic molecules. Low-temperature plasma treatment significantly improves the solubility of DCM in liquid phases.

[0062] 2) The gas emitted by the low-temperature plasma enters the UV-bubble tower system. When the gas flows upward, it will be captured by the droplets. Therefore, the residence time in the bubble tower system will be longer.

[0063] 3) There are two degradation pathways of DCM in the liquid phase: the most important is indirect oxidation by UV light decomposition of ozone to produce hydroxyl radicals; the second is direct oxidation by ozone attacking the H-Cl and C-Cl bonds of DCM.

[0064] 4) After the reaction is completed, air is continued to be introduced, and the DCM and intermediate organic matter that are not completely degraded in the liquid phase are further oxidized using O3+UV.

[0065] The utility model discloses a low-temperature plasma coupled ultraviolet-bubble tower system for degrading dichloromethane, which has the following advantages:

[0066] 1. Under the irradiation of ultraviolet lamps, the by-product O3 generated by low-temperature plasma is used as an oxidant, and the aerosol particles generated by discharge are retained in the water, reducing the threat to the atmospheric environment.

[0067] 2. Pretreatment of DCM with low-temperature plasma can increase the water solubility of DCM and increase the residence time of DCM in the UV-bubble tower device, thereby improving the removal efficiency and mineralization rate of DCM.

[0068] 3. No catalyst is needed. After completion, stop introducing air without DCM. Under the action of ozone + ultraviolet rays, the residual organic matter in the water can be completely oxidized without the problem of wastewater discharge and treatment.

[0069] The utility model discloses a low-temperature plasma coupled ultraviolet-bubble tower system for degrading dichloromethane, which is an economical and environmentally friendly system for degrading low-concentration DCM. DCM is introduced into the low-temperature plasma coupled ultraviolet-bubble tower system for degrading dichloromethane, so that it is fully converted into CO2 and H2O. The primary degradation mainly utilizes high-energy electrons, active oxygen species (·OH, ·O, ·N), ozone and other substances generated by the excitation of a flat dielectric barrier discharge to carry out primary oxidation of DCM. The secondary degradation mainly utilizes ultraviolet light to decompose the byproduct O3 produced by the primary degradation to produce ·OH to deeply oxidize the incompletely mineralized dichloromethane. After low-temperature plasma treatment, the solubility of DCM in the liquid phase can be increased, and the mass transfer efficiency between it and the active components in the liquid phase can be increased, which is conducive to its absorption and mineralization. In addition, the design of the ultraviolet-bubble tower not only prolongs the effective residence time of DCM in the system and provides conditions for the deep degradation of organic matter, but also can efficiently retain the byproducts generated in the previous step in the liquid phase, thereby avoiding pollution to the environment. After the reaction is complete, DCM-free air is introduced, allowing the recalcitrant organic pollutants in the liquid phase to be mineralized under the combined action of ozone and UV light. Therefore, this system only uses H₂O as a medium and does not involve issues such as catalyst deactivation and treatment.

[0070] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A system for degrading dichloromethane by low-temperature plasma coupled with ultraviolet-bubble tower, characterized in that: The invention comprises a low-temperature plasma device and an ultraviolet-bubble tower device; the first gas outlet (15) of the low-temperature plasma device is connected to the second gas inlet (7) of the ultraviolet-bubble tower device; the first gas inlet (14) and the first gas outlet (15) of the low-temperature plasma device are arranged on the same side; the ultraviolet-bubble tower device comprises a plurality of ultraviolet lamps (1), a plurality of bubbling zones arranged in a height direction, and a solution pool (5) arranged at the bottom; and the second gas outlet (8) is opened at the top of the ultraviolet-bubble tower device.

2. The system for degrading dichloromethane by low-temperature plasma coupled ultraviolet-bubble tower according to claim 1, characterized in that: The low-temperature plasma device comprises a high-voltage electrode (11), an insulating medium (12) and a grounding electrode (13) which are sequentially arranged in parallel.

3. The system for degrading dichloromethane by low-temperature plasma coupled ultraviolet-bubble tower according to claim 2, characterized in that: The high-voltage electrode (11) and the grounding electrode (13) are of equal size; the high-voltage electrode (11) and the grounding electrode (13) are both made of stainless steel; the high-voltage electrode (11) and the grounding electrode (13) are both hollow mesh structures, with square meshes, a side length of 20 to 30 mm, and a thickness of 1 to 3 mm.

4. The system for degrading dichloromethane by low-temperature plasma coupled ultraviolet-bubble tower according to claim 2, characterized in that: The insulating medium (12) is made of ceramic material and has a thickness of 1 to 3 mm. The distance between the high-voltage electrode (11) and the insulating medium (12) is equal to the distance between the insulating medium (12) and the grounding electrode (13), both of which are 8 to 12 mm.

5. The system for degrading dichloromethane by low-temperature plasma coupled ultraviolet-bubble tower according to claim 2, characterized in that: The low-temperature plasma device further comprises a shell (10); the high-voltage electrode (11), the insulating medium (12) and the grounding electrode (13) are installed in the shell (10); a first air inlet (14) and a first air outlet (15) are provided on the shell (10); the first air inlet (14) is arranged between the high-voltage electrode (11) and the insulating medium (12); and the first air outlet (15) is arranged between the insulating medium (12) and the grounding electrode (13).

6. The system for degrading dichloromethane by low-temperature plasma coupled ultraviolet-bubble tower according to claim 1, characterized in that: A demister (2) is arranged between the ultraviolet lamp (1) and the bubbling zone; the demister (2) is a folded plate structure; the demister (2) is 500 to 1000 mm away from the second air outlet (8); and the spacing between two bubbling zones is 1100 to 1500 mm.

7. The system for degrading dichloromethane by low-temperature plasma coupled ultraviolet-bubble tower according to claim 1, characterized in that: The bubbling zone comprises an overflow weir (3) located at the side and a sieve plate (9) located at the bottom and connected to the overflow weir (3); the sieve plate (9) is provided with a plurality of evenly arranged air holes (4).

8. The system for degrading dichloromethane by low-temperature plasma coupled ultraviolet-bubble tower according to claim 7, characterized in that: The ultraviolet lamp (1) is installed on the upper part of the ultraviolet-bubble tower device and penetrates and is fixed on the sieve plate (9).

9. The system for degrading dichloromethane by low-temperature plasma coupled ultraviolet-bubble tower according to claim 1, characterized in that: Circulation pumps (6) are arranged on both sides of the bottom of the UV-bubble tower device.

10. The system for degrading dichloromethane by low-temperature plasma coupled ultraviolet-bubble tower according to claim 9, characterized in that: The outlet of the solution pool (5) is connected to the inlet of the circulation pump (6) through a liquid delivery pipeline, and the outlet of the circulation pump (6) is connected to the bubbling area through a liquid delivery pipeline.

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