A gas-liquid dispersed discharge plasma water treatment device and treatment method thereof

Abstract

The present invention provides a gas-liquid dispersed discharge plasma water treatment device and treatment method. A gas cylinder with a gas valve, a mass flow controller, and an air inlet pipe are sequentially connected via a pipeline. A hollow high-pressure needle-tube electrode is inserted into a conical dielectric tube. The upper end of the hollow high-pressure needle-tube electrode is connected to a high-voltage power supply, and the top end is connected to the air inlet pipe. The bottom end of the conical dielectric tube is inserted into the waste liquid in the water storage tank. The branch pipe of the conical dielectric tube is connected to an air guide pipe for recovering the discharge exhaust gas into the waste liquid in the water storage tank. The water storage tank is placed on a horizontally placed steel plate ground electrode. One end of a circulating pump is connected to the water outlet of the water storage tank, and the other end is connected to the water inlet of the water storage tank. The present invention uses a gas-liquid discharge excited by a high-voltage power supply, avoiding the occurrence of thermal instability and facilitating the maintenance of discharge stability. At the same time, a conical dielectric tube is used to shield the discharge space, which further concentrates the plasma energy, shields the air, improves the discharge uniformity and stability, and facilitates the mass transfer of gas-phase active species to the liquid surface.

Description

Technical Field

[0001] The present invention belongs to the technical field of low-temperature plasma, and in particular relates to a gas-liquid diffuse discharge plasma water treatment device and a treatment method thereof. Technical Background

[0002] With the extensive use of antibiotics in medicine, animal husbandry and personal care products in recent years, a large amount of antibiotic-containing water has become an important source of water pollution. The antibiotics contained in sewage are highly stable, difficult to biodegrade and have potential toxicity. If they enter the environment, they will cause serious harm to human health and the ecological environment. Therefore, there is an urgent need to adopt an effective method to treat sewage containing antibiotics to meet discharge standards. Current sewage treatment methods such as physical and chemical methods, biological methods, and electrochemical methods can effectively degrade pollutants with simple components. However, due to the wide variety and complex structure of antibiotic pollution sources in water, the application of the above methods to the degradation of antibiotics in water has encountered challenges in terms of degradation efficiency and economy. Therefore, there is an urgent need to develop new and efficient sewage treatment technologies for the degradation of difficult-to-degrade pollutants such as antibiotics in water.

[0003] Atmospheric pressure gas-liquid discharge plasma is a new type of advanced oxidation technology that has emerged in recent years and has attracted particular attention in the field of environmental pollution control. This is mainly due to the fact that discharge plasma combines multiple physical and chemical effects such as ozone oxidation, ultraviolet degradation, free radical oxidation, and high-energy electron radiation. It has strong adaptability to the treatment objects and can not only degrade pollutants with simple structures, but also has obvious advantages in treating pollutants with complex compositions such as antibiotics. Traditional discharge plasma for water treatment uses gases such as air, argon, or helium as the discharge gas. The generated plasma interacts with the liquid, resulting in unstable discharge plasma, low plasma density and energy density, low energy utilization, inability to effectively utilize free radicals in a timely manner, and insufficient contact between active particles and organic pollutants. Therefore, it is of great significance to design a new type of large-scale, uniform and stable gas-liquid discharge plasma water treatment device to achieve high wastewater degradation efficiency. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a gas-liquid dispersed discharge plasma water treatment device, which includes a high-voltage power supply, a gas distribution system, a water flow meter and a gas-liquid discharge reactor.

[0005] The high-voltage power supply is a high-voltage nanosecond pulse power supply that can output a peak voltage of more than 10kV and a pulse frequency of more than 100Hz, which is continuously adjustable. The power supply parameters can be set according to actual needs during use.

[0006] The gas distribution system consists of a mass flow controller, an air inlet pipe, a gas valve and multiple gas cylinders; the gas cylinder with the gas valve, the mass flow controller and the air inlet pipe are connected in sequence through a pipeline, and the working gas is introduced into the reactor through the air inlet pipe.

[0007] The water flow meter is used to control the flow rate of water, and can introduce the waste liquid into the gas-liquid discharge reactor at a uniform speed.

[0008] The gas-liquid discharge reactor includes a hollow high-pressure needle tube electrode, a steel plate ground electrode, a conical dielectric tube with a branch pipe, a water tank and a circulation pump. The hollow high-pressure needle tube electrode is inserted into the conical dielectric tube, and the upper end of the hollow high-pressure needle tube electrode is connected to the high-voltage power supply via a high-voltage line, while its top end is connected to the air inlet pipe via a ferrule. The bottom end of the conical dielectric tube is inserted into the waste liquid in the water tank, and the branch pipe of the conical dielectric tube is connected to the air guide pipe for recycling the discharge exhaust gas into the waste liquid in the water tank. The water tank is placed on the horizontally placed steel plate ground electrode, the water inlet of the water tank is connected to a water flow meter, and a water valve is provided at the water outlet. One end of the circulation pump is connected to the water outlet of the water tank, and the other end is connected to the water inlet of the water tank, and is used for circulating the wastewater to achieve multiple treatments.

[0009] The orifice of the air duct must be kept above the orifice of the tapered medium tube, so that the pressure of the gas on the water in the air duct is lower than that in the tapered medium tube, ensuring that the exhaust gas is discharged from the air duct without affecting the stability of the liquid level in the tapered medium tube.

[0010] The conical medium pipe is fixed on a liftable bracket, and the depth of the conical medium pipe inserted into the waste liquid can be adjusted.

[0011] The device of the present invention is characterized by the following features: wastewater enters the water storage tank of the gas-liquid discharge reactor at a constant speed through a water flow meter. When the water level submerges the orifice of the tapered dielectric tube, it forms a shielded discharge space with the tapered dielectric tube. The gas distribution system is connected to the high-voltage electrode. After the working gas enters the discharge reactor, the control switch of the high-voltage power supply connected to the high-voltage electrode is turned on. When the high voltage breaks down the gas in the discharge space, a stable gas-liquid diffuse discharge plasma is generated between the high-voltage electrode and the liquid surface. In this process, the plasma and active substances generated by the discharge can directly react with antibiotics in the wastewater in the tapered dielectric tube. Furthermore, the large amount of insoluble active substances generated after the discharge is introduced into the wastewater through the air duct and can also react with the antibiotics in the wastewater, accelerating the degradation efficiency of the device. The wastewater in the reactor is re-introduced into the reactor via a circulation pump. After multiple treatments, the treated wastewater meets discharge standards and is then discharged from the reactor via a controlled water valve. The present invention can significantly alter the molecular structure of antibiotics such as trimethoprim in water, achieving high degradation efficiency. It can be used to treat antibiotic-containing water generated in daily life and medical applications.

[0012] The tapered dielectric tube should have a minimum inner diameter greater than 3 mm, a cone angle of 5-60°, and a height greater than 10 mm. The tapered dielectric tube and water reservoir can be made of any dielectric material, such as glass, polytetrafluoroethylene, or ceramic. The hollow high-voltage needle electrode can be made of any conductive metal or metal composite, such as stainless steel, tungsten, or copper.

[0013] The gas-liquid discharge reactor incorporates a conical dielectric tube within a hollow needle-water electrode structure. This tube forms a shielded discharge space with the liquid surface, enabling stable gas-liquid diffuse discharge plasma to be generated under atmospheric pressure. This stable gas-liquid diffuse discharge plasma exhibits advantages such as high plasma active species concentration, moderate power density, uniform energy distribution, high electron temperature, and low neutral gas temperature.

[0014] Stable gas-liquid diffuse discharge plasma has a relatively large plasma-liquid interaction area, which can efficiently transfer active species of gas-phase plasma into the liquid, achieving efficient sewage treatment effect.

[0015] When the tail gas of the discharge is introduced into the waste liquid in the water storage tank, a large number of active particles (such as ozone) that fail to enter the liquid in the discharge area and remain in the tail gas can be introduced into the waste liquid, thereby increasing the energy efficiency of the gas-liquid discharge plasma device in removing antibiotics such as trimethoprim from wastewater.

[0016] The discharge plasma generated by the device can be combined with the adsorbent to produce a plasma-adsorption synergistic effect with an enhanced effect, making full use of the attachment effect of the adsorbent and the physical and chemical effects generated by the discharge to improve the energy removal rate of the device for organic pollutants.

[0017] Before the wastewater enters the water flow meter, it should be initially filtered to remove larger particles.

[0018] Compared with existing technologies, the present device offers the following advantages: The gas-liquid discharge, stimulated by a high-voltage power supply, avoids thermal instability and helps maintain discharge stability. Furthermore, a conical dielectric tube shields the discharge space, further concentrating plasma energy and shielding the air, improving discharge uniformity and stability and facilitating mass transfer of gas-phase active species to the liquid surface. Furthermore, an air duct connected to a branch of the conical dielectric tube directs a large amount of insoluble active species generated by the discharge into the wastewater, effectively resolving the issue of insufficient contact between the plasma and organic matter in the water.

[0019] A treatment method of a gas-liquid dispersed discharge plasma water treatment device includes the following steps:

[0020] Step 1: Place the water tank on a horizontally placed steel plate ground electrode, which is grounded; waste liquid enters the water tank at a uniform speed through a water flow meter; a conical dielectric tube is fixed on a liftable bracket, and the lower end of the tube is inserted into the waste liquid; a hollow high-pressure needle tube electrode is inserted into the conical dielectric tube, with the upper end connected to the high-voltage power supply, the top end connected to the air inlet pipe through a ferrule, and the lower end placed on the horizontal line of the bottom end of the straight tube portion of the conical dielectric tube.

[0021] Step 2: Use tubing to connect the gas cylinder with a valve and the mass flow controller. Connect the inlet tube to the hollow high-pressure needle electrode through a ferrule. Adjust the mass flow controller to maintain a gas flow rate of more than 10 mL / min.

[0022] Step 3: Sewage is introduced into a water storage tank, and the flow rate is controlled by a water flow meter. Once the sewage submerges the lower end of the tapered medium tube, the high-voltage power supply is turned on. By adjusting the power supply voltage and frequency, as well as the gas flow rate and composition, a stable gas-liquid dispersed discharge plasma is achieved, which is then used to degrade organic pollutants in the water.

[0023] Step 4: Connect the branch of the tapered dielectric tube to an air duct. The other end of the air duct is inserted into the wastewater in the water storage tank. This duct circulates the plasma gas from the tapered dielectric tube back into the wastewater, increasing the reaction efficiency between the plasma active particles and pollutants in the wastewater. Note that the opening of the air duct remains above the opening of the tapered dielectric tube to ensure smooth exhaust discharge.

[0024] Step 5: The water outlet and water inlet of the water storage tank are connected through a pipeline with a circulation pump, which can circulate the waste liquid for multiple times to ensure that the treated waste liquid meets the discharge standards.

[0025] Step 6: After the waste liquid treated in the gas-liquid discharge reactor meets the discharge standard, the water is discharged from the outlet by controlling the water valve.

[0026] Step 7: After the processing is completed, turn off the high-voltage power switch first, and then turn off the water flow meter, high-voltage power supply and mass flow controller in sequence.

[0027] The beneficial effects of the present invention are:

[0028] In the process of the present invention, a conical dielectric tube is added to the hollow needle tube-water electrode structure to achieve a stable gas-liquid diffuse discharge plasma. It has the advantages of high concentration of plasma active species, moderate power density, uniform energy distribution, high electron temperature and low neutral gas temperature. It can efficiently transfer gas-phase plasma active species into the liquid, thereby achieving efficient sewage treatment effect.

[0029] The gas-liquid dispersed discharge plasma water treatment device of the present invention realizes long-term stable operation of gas-liquid discharge plasma under atmospheric pressure conditions. It has a long operating time, low manufacturing cost and treatment cost, meets the needs of sewage treatment, and can be used for large-scale industrial use.

[0030] By recycling the tail gas of the discharge reactor into the treated waste liquid, a large number of active particles that are not easily soluble in water (such as ozone) can be introduced into the waste liquid, increasing the contact efficiency between the active particles generated by discharge and organic pollutants, and improving the degradation efficiency of the discharge device on antibiotics in water.

[0031] The treatment process of the gas-liquid diffuse discharge plasma water treatment device of the present invention is realized under closed conditions, which can fully utilize the treatment effects of high-energy electrons, free radicals and ultraviolet radiation generated during the discharge process on sewage, and can achieve high-efficiency degradation of antibiotics such as trimethoprim in water. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the structure of the device of the present invention.

[0033] Figure 2 This is a diagram showing the efficiency of the device of the present invention in treating liquid containing the antibiotic trimethoprim. DETAILED DESCRIPTION

[0034] The present invention will be described in detail below with reference to the accompanying drawings. The examples given are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0035] A gas-liquid dispersed discharge plasma water treatment device mainly consists of a high-voltage power supply 1, a water flow meter 10, a gas-liquid discharge reactor and a gas distribution system.

[0036] The high voltage power supply 1 can output a peak voltage of more than 10 kV and a frequency of more than 100 Hz, which can be continuously adjustable. The power supply parameters can be set according to actual needs during use.

[0037] The gas-liquid discharge reactor is to fix the water tank 12 on the grounded steel plate ground electrode 14, and then vertically insert the conical dielectric tube 3 into the waste liquid of the water tank 12, and then insert the hollow high-pressure needle tube electrode 2 into the conical dielectric tube 3. The hollow high-pressure needle tube electrode 2 is connected to the high-voltage power supply 1, and its upper end is connected to the ferrule 4 and the air inlet pipe 5 in turn to connect to the gas distribution system. The water inlet of the water tank 12 is connected to the water flow meter 10, and the treated water flows out from the water outlet. One end of the circulation pump 9 is connected to the water outlet of the water tank 12, and the other end is connected to the water inlet of the water tank 12, and is used for the circulation flow treatment of the waste liquid. One end of the gas guide tube 11 is connected to the branch pipe of the tapered dielectric tube 3, and the other end is inserted into the waste liquid in the water storage tank 12, and the pipe opening of the gas guide tube 11 is ensured to be higher than the pipe opening of the tapered dielectric tube 3; after the gas entering the gas-liquid discharge reactor is broken down by high voltage, a gas-liquid diffuse discharge is generated between the high-voltage electrode and the liquid surface. At the same time, the discharge plasma gas can also be introduced into the waste liquid through the gas guide tube 11.

[0038] The gas distribution system consists of a mass flow controller 6, an air inlet pipe 5, a gas valve 7, and multiple gas cylinders 8. Multiple gas cylinders 8 with gas valves 7 are connected to the mass flow controller 6. One end of the air inlet pipe 5 is connected to the mass flow controller 6, and the other end is connected to the hollow high-pressure needle electrode 2 via a steel ferrule 4. The gas in the gas cylinders 8 can be nitrogen, argon, oxygen, or helium. The gas distribution system uses the mass flow controller 6 to control the gas flow rate, and all gases are mixed to form the working gas entering the reactor. The working gas used in this device is nitrogen, argon, or a mixture of helium and oxygen, with a gas flow rate controlled at above 10 mL / min.

[0039] The present invention provides a gas-liquid dispersed discharge plasma water treatment device, and the specific use method is as follows:

[0040] Step 1: Turn on the water flow meter 10, and wastewater flows into the water storage tank 12 at a uniform speed through the water flow meter 10. When the water level injected into the water storage tank 12 submerges the pipe mouth of the tapered medium tube 3, the tapered medium tube 3 and the liquid surface form a shielded discharge space.

[0041] Step 2: Open the gas valve 7 and adjust the gas flow rate by controlling the mass flow controller 6. The gas enters the discharge reactor through the hollow high-pressure needle tube electrode 2, and then is guided back to the waste liquid in the water storage tank 12 through the gas guide pipe 11 connected to the branch pipe of the conical medium tube 3.

[0042] Step 3: Turn on the circulation pump 9 to achieve the circulation of the waste liquid.

[0043] Step 4: After checking the above steps, turn on the high voltage power supply 1, and adjust the voltage and frequency of the power supply as well as the gas flow rate and composition to achieve a stable gas-liquid dispersed discharge plasma and act on the waste liquid; in addition, the discharge plasma gas generated in the conical medium tube 3 is also introduced into the waste liquid through the gas guide tube 11 to act on the antibiotics in the waste liquid. For example, Figure 2 As shown, the device of the present invention can achieve 100% removal of the antibiotic trimethoprim by using air as the working gas.

[0044] Step 6: After the processing is completed, first turn off the high-voltage power supply 1 and then turn off the high-voltage power supply 1, the air valve 7 and the water flow meter 10 in sequence.

[0045] In the present invention, the hollow high-voltage needle electrode 2 has an inner diameter of 2 mm and an outer diameter of 3 mm. The material of the hollow high-voltage needle electrode 2 can be any conductive metal or metal composite, such as stainless steel, tungsten, or copper. The tapered portion of the conical dielectric tube 3 should have a minimum inner diameter greater than 3 mm, a taper angle of 5-60°, and a height greater than 10 mm. The tapered dielectric tube 3 and water storage tank 12 can be made of any dielectric material, such as glass, polytetrafluoroethylene, or ceramic.

Claims

1. A gas-liquid dispersed discharge plasma water treatment device, characterized in that: It includes a high-voltage power supply (1), a gas distribution system, a water flow meter (10) and a gas-liquid discharge reactor; The gas distribution system comprises a mass flow controller (6), an air inlet pipe (5), an air valve (7) and a plurality of gas cylinders (8); the gas cylinder (8) with the air valve (7), the mass flow controller (6) and the air inlet pipe (5) are sequentially connected through a pipeline, and the working gas is introduced into the gas-liquid discharge reactor through the air inlet pipe (5); The gas-liquid discharge reactor comprises a hollow high-voltage needle tube electrode (2), a steel plate ground electrode (14), a conical medium tube with a branch pipe (3), a water storage tank (12) and a circulation pump (9); the hollow high-voltage needle tube electrode (2) is inserted into the conical medium tube (3), the upper end of the hollow high-voltage needle tube electrode (2) is connected to the high-voltage power supply (1) through a high-voltage line, and the top end thereof is connected to the air inlet pipe (5) through a ferrule (4); the bottom end of the conical medium tube (3) is inserted into the water storage tank (12) In the waste liquid, a branch pipe of the conical medium pipe (3) is connected to the air guide pipe (11) for recovering the discharge tail gas into the waste liquid of the water storage tank (12); the water storage tank (12) is placed on a horizontally placed steel plate ground electrode (14); the water inlet of the water storage tank (12) is connected to the water flow meter (10), and the water outlet is provided with a water valve (13); one end of the circulation pump (9) is connected to the water outlet of the water storage tank (12), and the other end is connected to the water inlet of the water storage tank (12), for circulating the waste water to achieve multiple treatments; The orifice of the air guide tube (11) is maintained above the orifice of the tapered medium tube (3).

2. A gas-liquid dispersed discharge plasma water treatment device according to claim 1, characterized in that: The conical medium pipe (3) is fixed on a liftable bracket, and the depth of the conical medium pipe (3) inserted into the waste liquid is adjusted.

3. A gas-liquid dispersed discharge plasma water treatment device according to claim 1, characterized in that: The high-voltage power supply (1) is a high-voltage nanosecond pulse power supply that can output a peak voltage of more than 10 kV and a pulse frequency of more than 100 Hz and is continuously adjustable.

4. A gas-liquid dispersed discharge plasma water treatment method, characterized in that: Using the gas-liquid dispersed discharge plasma water treatment device according to any one of claims 1 to 3, the method comprises the following steps: Step 1: Place the water storage tank (12) on a horizontally placed steel plate ground electrode (14), which is grounded; waste liquid flows into the water storage tank (12) at a uniform speed through a water flow meter (10); a conical medium tube (3) is fixed on a liftable bracket, and the lower end of the tube is inserted into the waste liquid; a hollow high-pressure needle tube electrode (2) is inserted into the conical medium tube (3), the upper end of which is connected to the high-voltage power supply (1), the top end of which is connected to the air inlet pipe (5) through a ferrule (4), and the bottom end of which is placed on the horizontal line of the bottom end of the straight tube portion of the conical medium tube (3); Step 2: Use a pipeline to connect the gas cylinder (8) with the gas valve (7) and the mass flow controller (6) in sequence, and connect the gas inlet pipe (5) to the hollow high-pressure needle electrode (2) through the ferrule (4); control the gas flow rate by adjusting the mass flow controller (6); Step 3: The sewage is introduced into the water storage tank (12), and the water flow rate is controlled by the water flow meter (10); when the sewage submerges the bottom end of the conical medium tube (3), the high-voltage power supply (1) is turned on, and by adjusting the voltage and frequency of the power supply as well as the gas flow rate and composition and other parameters, a stable gas-liquid diffuse discharge plasma is achieved, and is used to degrade organic pollutants in the water; Step 4: The branch pipe of the conical medium pipe (3) is connected to the air guide pipe (11), and the other end of the air guide pipe (11) is inserted into the waste liquid in the water storage tank (12) to circulate the discharge plasma gas in the conical medium pipe (3) into the waste liquid to increase the reaction efficiency of the plasma active particles and the pollutants in the waste liquid; the pipe opening of the air guide pipe (11) is kept above the pipe opening of the conical medium pipe (3) to ensure smooth discharge of the exhaust gas; Step 5: The water outlet and water inlet of the water storage tank (12) are connected through a pipeline with a circulation pump (9), and the waste liquid is circulated for multiple times to ensure that the waste liquid meets the discharge standards after treatment; Step 6: After the waste liquid treated in the gas-liquid discharge reactor reaches the discharge standard, the water is discharged from the outlet by controlling the water valve (13); Step 7: After the treatment is completed, first turn off the high-voltage power supply (1) switch, and then turn off the water flow meter (10), the high-voltage power supply (1) and the mass flow controller (6) in sequence.

Images