Device for degrading organic wastewater through double-medium falling film dielectric barrier discharge

Abstract

The invention relates to the technical field of low-temperature plasma, and discloses a device for degrading organic wastewater by double-medium falling film dielectric barrier discharge, which comprises an upper water tank and a lower water tank, a quartz medium outer tube is coaxially arranged between the upper water tank and the lower water tank, and a quartz medium inner tube is coaxially arranged in the quartz medium outer tube. The inner part of the quartz medium inner tube is filled with high-purity nano copper powder, the outer side of the quartz medium outer tube is wrapped with a copper strip, and a cavity between the outer side wall of the quartz medium inner tube and the inner side wall of the quartz medium outer tube wrapped with the copper strip forms a discharge area. A coaxial double-layer quartz medium tube structure is adopted, and a cylindrical baffle and a round hole arranged in the upper water tank are combined, so that organic wastewater forms a uniform, continuous and stable thin-layer liquid film along the inner wall of the quartz medium outer tube under the action of gravity, and the working efficiency is improved; and meanwhile, the flowing liquid film continuously takes away Joule heat generated by discharging in the reaction process, so that the effective utilization rate of energy is improved.

Description

Technical Field

[0001] This invention relates to the field of low-temperature plasma technology, specifically to a device for degrading organic wastewater using a dual-dielectric falling film dielectric barrier discharge. Background Technology

[0002] With the acceleration of global industrialization, water pollution has become increasingly severe. In particular, industries such as dyeing, pharmaceuticals, chemicals, and mining discharge high-concentration, non-biodegradable, toxic, and harmful organic wastewater, posing a serious threat to ecosystems and human health. This type of wastewater has complex composition and high chemical stability, and traditional water treatment methods have significant limitations: physical adsorption methods only achieve pollutant transfer and are prone to secondary pollution; chemical methods such as Fenton oxidation and ozone oxidation consume large amounts of reagents and are costly; biological methods have poor adaptability to highly toxic and high-salinity wastewater and have long treatment cycles. Therefore, developing efficient, green, and economical technologies for the degradation of organic wastewater has become a research hotspot in the field of environmental governance.

[0003] Low-temperature plasma technology, as an advanced oxidation technology, can generate highly reactive oxidizing species such as ·OH, O3, and H2O2 at room temperature and pressure, non-selectively degrading organic pollutants. It has advantages such as high reaction efficiency and no need to add large amounts of chemical reagents. Among them, dielectric barrier discharge is widely used in organic wastewater degradation research due to its uniform discharge, high energy density, and simple device structure.

[0004] However, conventional dielectric barrier discharge reactors face a core bottleneck when used for water treatment: low mass transfer efficiency of active species from the gas phase to the liquid phase. In traditional reactors, the gas-liquid contact area between wastewater and plasma is limited, and spraying or bubbling methods are usually used, resulting in high mass transfer resistance at the two-phase interface, which limits the full contact between active free radicals and pollutants. At the same time, some of the input energy is converted into heat rather than active substances, and the uneven electric field distribution leads to low energy utilization. In addition, complex organic molecules are often only partially degraded, resulting in poor operational stability. Furthermore, the high heat generated by discharge requires forced cooling, which increases the complexity of the system and energy consumption. Summary of the Invention

[0005] The purpose of this invention is to provide a device for degrading organic wastewater using a dual-dielectric falling film dielectric barrier discharge, in order to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A device for degrading organic wastewater using a dual-dielectric falling film dielectric barrier discharge includes an upper tank and a lower tank. A quartz dielectric outer tube is coaxially arranged between the upper and lower tanks. An inner quartz dielectric tube is coaxially arranged inside the outer quartz dielectric tube. The inner quartz dielectric tube is filled with high-purity nano-copper powder. A copper strip is wrapped around the outside of the outer quartz dielectric tube. A discharge region is formed by the cavity between the outer wall of the inner quartz dielectric tube and the inner wall of the copper strip wrapped around the outer quartz dielectric tube. The upper end of the high-purity nano-copper powder filling the inner quartz dielectric tube is connected to a grounding electrode via a wire. One end of the copper strip is connected to a high-voltage power supply via a wire. A coaxial cylindrical baffle is arranged inside the upper tank, outside the outer quartz dielectric tube. The cylindrical baffle has several circular holes evenly distributed in a ring shape near the upper part.

[0008] As a further embodiment of the present invention: the upper and lower ends of the outer quartz medium tube are respectively connected to the upper water tank and the lower water tank, the lower end of the inner quartz medium tube is a closed end, and the upper end of the inner quartz medium tube is an open end, and the inner quartz medium tube extends upward through the inner side of the upper water tank.

[0009] As a further embodiment of the present invention: a fixing frame is provided at the lower part between the inner side of the outer tube of the quartz medium and the outer side of the inner tube of the quartz medium, and an acrylic cover is provided on the outer side of the upper water tank and the lower water tank for fixing.

[0010] As a further embodiment of the present invention: an air inlet is provided at the upper end of the outer side of the upper water tank, and one end of the air inlet is connected to an air blower through an air pipe; an air outlet is provided at the upper end of the outer side of the lower water tank.

[0011] As a further embodiment of the present invention: a water inlet is provided at the lower end of the outer side of the upper water tank, and a water outlet is provided at the lower end of the outer side of the lower water tank; a peristaltic pump is connected between the water inlet and the water outlet via a water pipe.

[0012] As a further embodiment of the present invention: the copper strip is wrapped around the outside of the quartz medium outer tube with epoxy resin adhesive, the spacing of the copper strip on the outside of the quartz medium outer tube is 1-1.5cm, and the end of the copper strip not connected to the wire is arc-shaped.

[0013] As a further aspect of the present invention: a monitoring device for acquiring circuit parameters is also connected between the grounding electrode and the high-voltage power supply via a wire. The monitoring device includes a high-voltage probe, a low-voltage probe, a current probe, and a digital storage oscilloscope.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] This invention employs a coaxial double-layer quartz media tube structure, combined with a cylindrical baffle and uniformly spaced circular holes inside the upper water tank. This allows organic wastewater to form a uniform, continuous, and stable thin liquid film along the inner wall of the outer quartz media tube under gravity. This significantly increases the gas-liquid contact area, enabling highly oxidizing active species generated by plasma to be efficiently transferred from the gas phase to the liquid phase, overcoming the bottleneck of low mass transfer efficiency in traditional DBD reactors. Simultaneously, the flowing liquid film continuously carries away the Joule heat generated by the discharge during the reaction process, maintaining the low temperature of the reaction system, reducing ozone decomposition and energy loss caused by high temperatures, and significantly improving energy utilization efficiency.

[0016] By sealing high-purity nano-copper powder, which serves as the grounding electrode, inside the inner quartz tube, the conductive components are physically isolated from the highly corrosive organic wastewater, thus avoiding the risk of electrode corrosion. The copper strip wrapped around the outer wall of the outer quartz tube is fixed by an epoxy resin vacuum degassing and potting process, which effectively eliminates air bubbles in the encapsulation layer, avoiding the problems of local breakdown and reduced insulation performance caused by air bubbles, and greatly enhancing the corrosion resistance and long-term operational stability of the device. Attached Figure Description

[0017] Figure 1 A schematic diagram of a device for degrading organic wastewater using a dual-dielectric falling film dielectric barrier discharge.

[0018] Figure 2 This is a top view schematic diagram of the upper water tank in a device for degrading organic wastewater using a dual-dielectric falling film dielectric barrier discharge.

[0019] Figure 3 This is a schematic diagram of the upper and lower water tanks in a device for degrading organic wastewater using a dual-dielectric falling film dielectric barrier discharge.

[0020] In the diagram: 1. Upper water tank; 2. Lower water tank; 3. Aeration device; 4. Peristaltic pump; 5. Water inlet; 6. Water outlet; 7. Inner tube of quartz medium; 8. Outer tube of quartz medium; 9. High-purity nano copper powder; 10. Air inlet; 11. Air outlet; 12. Grounding electrode; 13. Discharge area; 14. Copper strip; 15. Monitoring equipment; 16. High-voltage power supply; 17. Fixing frame; 18. Acrylic cover; 19. Cylindrical baffle; 20. Circular hole. Detailed Implementation

[0021] Please see Figures 1-3In this embodiment of the invention, a device for degrading organic wastewater by dual-dielectric falling film dielectric barrier discharge includes an upper water tank 1 and a lower water tank 2, both of which are 3D printed. A quartz dielectric outer tube 8 is coaxially arranged between the upper water tank 1 and the lower water tank 2. A quartz dielectric inner tube 7 is coaxially arranged inside the quartz dielectric outer tube 8. The interior of the quartz dielectric inner tube 7 is filled with high-purity nano-copper powder 9. A copper strip 14 is wrapped around the outside of the quartz dielectric outer tube 8. The cavity between the outer wall of the quartz dielectric inner tube 7 and the copper strip 14 wrapped around the outside of the quartz dielectric outer tube 8 forms a discharge region 1. 3; The upper end of the high-purity nano copper powder 9 filled inside the quartz inner tube 7 is connected to the grounding electrode 12 through a wire, and one end of the copper strip 14 is connected to the high-voltage power supply 16 through a wire. The peak-to-peak voltage of the high-voltage power supply 16 is 18 to 28 kV, and the discharge frequency of the power supply is 6000 to 8000 Hz. The optimal peak voltage and the optimal discharge frequency can be selected according to the actual situation. Inside the upper water tank 1, a coaxial cylindrical baffle 19 is set outside the quartz outer tube 8. Near the upper part of the cylindrical baffle 19, several circular holes 20 are evenly opened in a ring. For example, the upper water tank 1 and the lower water tank 2 have a diameter of 90mm, a height of 65mm, and a wall thickness of 5mm; the outer quartz medium tube 8 has an inner diameter of 20mm, a length of 300mm, and a wall thickness of 1mm; the inner quartz medium tube 7 has an inner diameter of 15mm, a length of 400mm, and a wall thickness of 1mm; the cylindrical baffle 19 has an inner diameter of 40mm, a height of 45mm, and a wall thickness of 5mm; therefore, the diameter of the circular hole 20 is 2mm, and the distance between the circular hole 20 and the top of the cylindrical baffle 19 is 6mm, with a 2mm interval between the inner sides of two adjacent circular holes. The specific calculation method for the device's degradation efficiency is: the ratio of the difference between the initial concentration of wastewater before degradation and the concentration of wastewater after treatment to the initial concentration.

[0022] exist Figure 1 and Figure 3In this system, the upper and lower ends of the quartz dielectric outer tube 8 are connected to the upper water tank 1 and the lower water tank 2, respectively. A uniform water film overflowing from the circular hole 20 on the upper water tank 1 flows along its inner wall into the discharge area 13 through the opening at the upper inner end of the quartz dielectric outer tube 8. Wastewater from the completed discharge reaction flows into the lower water tank 2 through the opening at the lower inner end of the quartz dielectric outer tube 8. The lower end of the quartz dielectric inner tube 7 is closed, and the upper end is open. The quartz dielectric inner tube 7 extends upwards through the inner side of the upper water tank 1. Since the quartz dielectric inner tube 7 itself is an insulator, it must rely on its internal... High-purity nano-copper powder 9 serves as a conductor and is connected to the grounding electrode 12. Therefore, high-purity nano-copper powder 9 can be filled into the inner tube 7 of the quartz medium through the open end and compacted, and then sealed. The closed end at the bottom can prevent wastewater or gas from entering the tube and corroding the copper powder, and at the same time, it acts as a dielectric barrier layer to participate in the discharge. When high voltage is applied to the outer tube 8 of the quartz medium, the electric field must penetrate this layer of quartz glass to act on the discharge area 13. The closed end ensures that only the quartz material (not the metal) directly faces the discharge plasma, thereby achieving uniform and stable discharge and preventing arc discharge.

[0023] exist Figure 1 and Figure 3 In the middle, a fixing frame 17 is provided at the lower part between the inner side of the outer quartz medium tube 8 and the outer side of the inner quartz medium tube 7. The fixing frame 17 can securely fix the inner quartz medium tube 7 inside the outer quartz medium tube 8 and ensure that the inner quartz medium tube 7 and the outer quartz medium tube 8 are coaxial, so as not to cause the discharge area 13 to be wider on one side and narrower on the other, so as to prevent unnecessary arc discharge due to excessive electric field concentration caused by excessively small local gaps. An acrylic cover 18 is provided on the outer side of the upper water tank 1 and the lower water tank 2 for fixing. The acrylic cover 18 supports the upper water tank 1 and the lower water tank 2 to prevent instability after they are filled with water.

[0024] exist Figure 1 and Figure 3 In this system, an air inlet 10 is provided at the upper outer end of the upper water tank 1, and one end of the air inlet 10 is connected to an aeration device 3, such as an air pump, via an air pipe; an air outlet 11 is provided at the upper outer end of the lower water tank 2; the gas is pumped into the upper water tank 1 by the aeration device 3 and then into the discharge area 13. On the one hand, the gas molecules are ionized under the action of a strong electric field to form a low-temperature plasma containing high-energy electrons, free radicals (such as oxygen atoms), excited-state particles, etc. On the other hand, the gas flows into the discharge area from the air inlet 10 at one end of the upper water tank 1 and is finally discharged from the air outlet 11 at one end of the lower water tank 2. This flow process ensures the renewal of the gas composition inside the discharge area 13, avoids gas depletion or excessively high local temperature due to long-term discharge, and efficiently transports the active substances generated in the discharge area 13 to the liquid film surface, thereby realizing the continuous and efficient degradation of organic wastewater.

[0025] exist Figure 1 and Figure 3 In the upper water tank 1, an inlet hole 5 is provided at the lower outer end, and an outlet hole 6 is provided at the lower outer end of the lower water tank 2. A peristaltic pump 4 is connected between the inlet hole 5 and the outlet hole 6 by a water pipe. The peristaltic pump 4 accurately extracts the organic wastewater to be treated or partially treated from the lower water tank 2 and transports it to the higher upper water tank 1 through the water pipe. The flow rate of the liquid entering the upper water tank 1 is controlled. When the water level in the upper water tank 1 reaches a certain height, the wastewater flows into the discharge area 13 in the form of a liquid film from the circular hole 20 on the cylindrical baffle 19 inside the upper water tank 1 under the action of gravity. Since the degradation of organic wastewater is usually not completed in one flow, the peristaltic pump 4 makes the liquid form a closed loop: lower water tank 2 → peristaltic pump 4 → upper water tank 1 → discharge area 13 → lower water tank 2.

[0026] If the flow rate is too high, the liquid film will be too thick or even form a water column, which will damage the discharge stability. If the flow rate is too low, the liquid film may be discontinuous, resulting in a dry area in the discharge region 13, which may damage the inner tube 7 and the outer tube 8 of the quartz medium or reduce the treatment efficiency. Therefore, the precise flow rate provided by the peristaltic pump 4 ensures that the wastewater can form a uniform, continuous and stable thin liquid film at this circular hole 20 and flow slowly down the inner wall of the outer tube 8 of the quartz medium.

[0027] Preferably, the copper strip 14 is wrapped around the outside of the quartz dielectric outer tube 8 with epoxy resin adhesive. The spacing between the copper strips 14 on the outside of the quartz dielectric outer tube 8 is 1-1.5 cm, and the end of the copper strip 14 not connected to the wire is arc-shaped. The arc shape increases the radius of curvature of the edge of the copper strip 14, reducing unnecessary corona discharge. With a spacing of 1-1.5 cm, the copper strips 14 maintain a certain insulation distance, and through the edge effect of adjacent copper strips 14, a continuous and uniform electric field superposition area is formed on the surface of the quartz dielectric outer tube 8. This allows the gas in the discharge area 13 to be uniformly ionized, rather than being violently discharged only at certain points. The number of turns of the copper strip 14 can be 4.5 turns to ensure that the copper strip 14 can completely cover the main reaction area through which the liquid film flows.

[0028] The process of winding the copper strip 14 around the outside of the quartz dielectric outer tube 8 is as follows:

[0029] First, take a certain amount of epoxy resin A glue (main glue), add half the weight of A glue B glue (fixing agent), and slowly stir along the container wall in the same direction for 2-3 minutes until the glue becomes transparent. Then put the prepared glue into a vacuum drying oven and evacuate it to about 0.9 kPa for 10-15 minutes to eliminate air bubbles.

[0030] Use transparent tape to stick to both sides of an A4 sheet of paper. Wrap this A4 sheet around the outside of the quartz medium outer tube 8 with the copper strip 14, with a fixing device at the bottom and a gap in the middle. Pour the bubble-removing glue along the outer wall of the quartz medium outer tube 8 into the space between the A4 sheet and the glue. Then, put the quartz medium outer tube 8 into a vacuum drying oven and evacuate it to 0.9 kPa. Maintain the temperature at about 25°C for 18 to 24 hours. This will fix the copper strip 14 to the quartz medium outer tube 8, and there will be no air bubbles in the epoxy resin glue.

[0031] exist Figure 1 In the circuit, a monitoring device 15 for acquiring circuit parameters is connected between the grounding electrode 12 and the high-voltage power supply 16 via a wire. The monitoring device 15 includes a high-voltage probe, a low-voltage probe, a current probe, and a digital storage oscilloscope.

[0032] High-voltage probes, such as the Tektronix P6015A, are used to determine whether the power supply output meets the experimental settings, such as 18–28 kV, and to analyze the discharge initiation voltage and breakdown characteristics.

[0033] Low-voltage probes, such as the Tektronix TPP0201, are used to monitor the synchronous signal output of the power supply, measure the signal of the low-voltage control circuit inside the power supply, and measure the electrical signals of other auxiliary equipment at non-high-voltage measurement points.

[0034] Current probes, such as the Pearson model 411, are used to accurately capture current pulse waveforms in the microsecond or even nanosecond range during dielectric barrier discharge. By observing the current waveform, it is possible to determine whether the discharge is a uniform glow discharge or a filamentary streamer discharge (micro-discharge), thereby assessing the intensity and uniformity of the discharge.

[0035] Digital storage oscilloscopes, such as the Agilent DSO-X4054A, receive signals from high-voltage and current probes, display voltage-current waveforms in real time, and calculate discharge power, frequency, and phase difference.

[0036] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A device for degrading organic wastewater by dual-dielectric falling film dielectric barrier discharge, comprising an upper water tank (1) and a lower water tank (2), characterized in that, A quartz medium outer tube (8) is coaxially arranged between the upper water tank (1) and the lower water tank (2). A quartz medium inner tube (7) is coaxially arranged inside the quartz medium outer tube (8). The interior of the quartz medium inner tube (7) is filled with high-purity nano copper powder (9). A copper strip (14) is wrapped around the outside of the quartz medium outer tube (8). The cavity between the outer wall of the quartz medium inner tube (7) and the inner wall of the copper strip (14) wrapped around the outside of the quartz medium outer tube (8) A discharge region (13) is formed; the upper end of the high-purity nano copper powder (9) filled inside the quartz dielectric inner tube (7) is connected to the grounding electrode (12) through a wire, and one end of the copper strip (14) is connected to the high-voltage power supply (16) through a wire. A coaxial cylindrical baffle (19) is provided inside the upper water tank (1) on the outside of the quartz dielectric outer tube (8). The cylindrical baffle (19) has several circular holes (20) evenly opened in a ring near the upper part.

2. The apparatus for degrading organic wastewater by dual-dielectric falling film dielectric barrier discharge according to claim 1, characterized in that, The upper and lower ends of the outer quartz medium tube (8) are connected to the upper water tank (1) and the lower water tank (2) respectively. The lower end of the inner quartz medium tube (7) is a closed end, and the upper end of the inner quartz medium tube (7) is an open end. The inner quartz medium tube (7) extends upward through the inner side of the upper water tank (1).

3. The device for degrading organic wastewater by dual-dielectric falling film dielectric barrier discharge according to claim 1, characterized in that, A fixing frame (17) is provided at the lower part between the inner side of the outer tube of the quartz medium (8) and the outer side of the inner tube of the quartz medium (7), and an acrylic cover (18) is provided on the outer side of the upper water tank (1) and the lower water tank (2).

4. The apparatus for degrading organic wastewater by dual-dielectric falling film dielectric barrier discharge according to claim 1, characterized in that, An air inlet (10) is provided at the upper end of the outer side of the upper water tank (1), and one end of the air inlet (10) is connected to an air blower (3) through an air pipe. An air outlet (11) is provided at the upper end of the outer side of the lower water tank (2).

5. The apparatus for degrading organic wastewater by dual-dielectric falling film dielectric barrier discharge according to claim 1, characterized in that, The upper water tank (1) has an inlet hole (5) at the lower outer end, and the lower water tank (2) has an outlet hole (6) at the lower outer end. A peristaltic pump (4) is connected between the inlet hole (5) and the outlet hole (6) by a water pipe.

6. The apparatus for degrading organic wastewater by dual-dielectric falling film dielectric barrier discharge according to claim 1, characterized in that, The copper strip (14) is wrapped around the outside of the quartz medium outer tube (8) with epoxy resin glue. The spacing of the copper strip (14) on the outside of the quartz medium outer tube (8) is 1-1.5cm, and the end of the copper strip (14) that is not connected to the wire is arc-shaped.

7. The apparatus for degrading organic wastewater by dual-dielectric falling film dielectric barrier discharge according to claim 1, characterized in that, The grounding electrode (12) and the high-voltage power supply (16) are also connected by a wire to a monitoring device (15) for acquiring circuit parameters. The monitoring device (15) includes a high-voltage probe, a low-voltage probe, a current probe and a digital storage oscilloscope.

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