Micro-channel gas-liquid two-phase micro-discharge organic wastewater degradation device

Abstract

The application discloses a kind of micro-channel gas-liquid two-phase micro-discharge organic wastewater degradation devices, the device includes organic wastewater tank, plunger pump, micro-channel chip, gas tank, collection tank, plasma power supply, oscilloscope.Organic wastewater tank is used to store wastewater with organic pollutants;Plunger pump is used to provide power for liquid phase to transport;Micro-channel chip is the core device for degrading organic pollutants in wastewater;Gas tank is used to store ozone or oxygen or air and other gases;Collection tank is used to store organic wastewater that has been degraded;Plasma power supply is used to provide power for dielectric barrier discharge technology;Oscilloscope is used to observe the power of plasma power supply.The wave-shaped electrode of the application and the shape of dielectric barrier layer are consistent, which fully utilizes the effective discharge area of the electrode and improves the energy utilization rate;Through the flow focusing type micro-bubble generation structure in the micro-channel chip, micro-bubbles are generated in the flow channel, and the organic wastewater is treated by the combined action of micro-bubbles, hydrodynamic cavitation and gas-liquid two-phase dielectric barrier discharge, realizing efficient and rapid degradation of organic pollutants in wastewater.

Description

Technical Field

[0001] This invention relates to a microfluidic gas-liquid two-phase micro-discharge organic wastewater degradation device, belonging to the field of wastewater treatment technology. Background Technology

[0002] Organic wastewater contains a wide variety of organic matter, including oils, proteins, cellulose, and dyes. If untreated or improperly treated organic wastewater is discharged, it can cause a series of harms to the ecological environment. When organic wastewater is rich in nitrogen and phosphorus, it can lead to the overgrowth of algae and other microorganisms, thereby damaging aquatic ecosystems and weakening the water body's self-purification capacity. Organic wastewater in water relies on microorganisms for degradation, a process that consumes large amounts of dissolved oxygen, thus affecting the survival of aquatic organisms. In addition, organic wastewater also pollutes soil, damages groundwater sources, and threatens human health. With the continuous improvement of environmental protection regulations in my country, the emission standards for organic pollutants are constantly increasing. To meet these higher treatment standards, research on organic wastewater degradation technologies is essential. Therefore, the effective treatment and management of organic wastewater is a necessary measure to protect the environment, safeguard human health, and promote sustainable development.

[0003] Currently, commonly used methods for degrading organic wastewater both domestically and internationally include biological treatment, photocatalysis, and ecological engineering. Biological treatment utilizes the ability of microorganisms to convert organic matter into harmless substances to treat organic wastewater. However, this method has a long treatment time and requires a balanced environment for the microorganisms in terms of temperature, pH, oxygen, and nutrients. Photocatalysis uses ultraviolet or visible light to irradiate organic matter, causing a chemical reaction. However, this method is only suitable for some organic pollutants that are capable of chemical reactions. Ecological engineering degrades organic matter by simulating the combined effects of wetland vegetation, microorganisms, and soil in natural wetland systems. However, this method requires a large area and is only suitable for treating low to medium concentrations of organic wastewater.

[0004] Patent CN112087854A discloses a dielectric barrier discharge plasma generator. This device uses a coaxial double-layered tube as the plasma reaction tube, with high-voltage electrodes arranged in the center of the inner tube. A liquid electrode is used between the inner and outer tubes, and the working fluid in the plasma reaction tube is a single-phase gas. The liquid electrode used in this device involves a highly complex preparation process and high preparation costs, and requires more frequent maintenance to maintain the stability of electrode performance. In addition, the various active substances generated in the single-phase discharge process generally have a short existence time. Except for ozone molecules, which have a half-life on the order of minutes, the half-lives of other active substances are only on the order of milliseconds or microseconds. Many active substances are deactivated before contacting the waste liquid. In contrast, in the gas-liquid two-phase discharge process, because the bubbles and waste liquid are fully mixed in the microchannel, the active substances can immediately react with pollutants after generation. Therefore, the degradation effect and energy utilization rate of the single-phase discharge device provided by this patent are far lower than those of the gas-liquid two-phase discharge device.

[0005] Patent CN111470587A discloses a bubble-film dielectric barrier discharge plasma pollutant treatment device. This device uses a flow meter and a microporous aeration device to introduce high-pressure gas into water to form a gas film. The outer layer of the tube wall includes an insulating dielectric layer and high-voltage electrodes. The electrodes discharge high voltage onto the wastewater containing the gas film to degrade organic matter. This device prepares a gas-liquid two-phase mixture using microporous aeration. However, due to insufficient shear force of the organic wastewater on the gas, the formed bubbles are relatively large, resulting in a small specific surface area and low gas-liquid mass transfer intensity, thus reducing mass transfer efficiency and making the device less efficient at degrading organic wastewater.

[0006] In summary, most existing degradation devices degrade wastewater or waste gas by discharging a single gas without using a dielectric barrier layer. However, this discharge process results in a large amount of short-lived active substances becoming inactive before reacting with pollutants, leading to a significant waste of oxidant and thus low energy utilization and poor degradation effect. Although a few degradation devices use gas-liquid two-phase discharge to degrade wastewater or waste gas, the mixing effect of the gas and liquid phases is poor, the gas-liquid mass transfer intensity is low, and because ozone is poorly soluble in water, insufficient mixing of the gas and liquid phases leads to some ozone not being effectively utilized, thereby weakening the degradation effect.

[0007] Therefore, improving the mixing efficiency of the gas-liquid two phases and enhancing the discharge effect of the degradation device are urgent problems to be solved in the field of organic wastewater degradation. Summary of the Invention

[0008] To address the aforementioned problems, this invention provides a method and apparatus for the degradation of organic wastewater using microfluidic gas-liquid two-phase micro-discharge. Organic wastewater and air are respectively pumped into a microfluidic chip at a fixed ratio via a plunger pump and a gas tank. The liquid and gas phases are thoroughly mixed into a gas-liquid two-phase flow through the cross-structure of the microfluidic chip. The organic pollutants are then degraded into water and carbon dioxide through the multi-stage expansion and contraction structure of the microfluidic chip's reaction chamber and the discharge action of the electrodes. Considering that a single degradation cycle may not completely degrade all organic pollutants when their concentration is too high, multiple cycles can be performed using a collection tank and a second plunger pump to re-inject the wastewater into the microfluidic chip for further degradation.

[0009] In a first aspect, the present invention provides a microfluidic gas-liquid two-phase micro-discharge organic wastewater degradation device, comprising:

[0010] Organic wastewater tank, used to store organic wastewater;

[0011] A first plunger pump is connected to the organic wastewater tank;

[0012] Gas tanks are used to store and provide discharge gas for gas-liquid two-phase micro-discharge processes;

[0013] Collection tanks are used to store degraded organic wastewater;

[0014] A microfluidic chip is included, in which an organic wastewater tank, a first plunger pump, a gas tank, and a collection tank are coupled to the microfluidic chip. The microfluidic chip is configured with a mixing channel assembly and a discharge reaction chamber connecting the mixing channel assembly and the collection tank. The discharge reaction chamber includes a reaction chamber channel, a dielectric barrier layer, and a corrugated discharge electrode. The reaction chamber channel has a multi-segment continuous expanding and contracting structure with corrugated walls. The dielectric barrier layer and the corrugated discharge electrode are corrugated thin plates with identical shape and dimensions, and are tightly bonded together to form an integrated corrugated structure. The shape of the corrugated structure is identical to the shape of the reaction chamber channel wall. The discharge spacing of the wavy discharge electrodes increases as the reaction chamber flow channel expands and decreases as it contracts, forming a discharge structure with alternating spacing sizes. This configuration allows for full utilization of the effective discharge area of ​​the electrodes, enabling all discharge areas to be used for gas-liquid two-phase plasma ionization within the microchannel, significantly improving the energy utilization rate of the device. Furthermore, the alternating spacing of the wavy discharge electrodes ensures a sufficiently high electric field strength in the discharge region while preventing electrode overheating.

[0015] A plasma power supply is connected to the discharge reaction chamber of the microfluidic chip and provides electrical energy for the plasma discharge process; and

[0016] An oscilloscope, connected to the plasma power supply, is used to detect the plasma discharge power in real time.

[0017] Organic wastewater is pumped into the microfluidic chip by the first plunger pump, where a plasma degradation reaction occurs in the discharge reaction chamber inside the microfluidic chip.

[0018] Furthermore, the dielectric barrier layer is made of a ceramic layer with a high dielectric constant. Since the corrugated discharge electrode and the dielectric barrier layer are tightly bonded, the electric field strength generated by the corrugated discharge electrode is related to the external dimensions of the dielectric barrier layer and the corrugated discharge electrode. The reduced field strength expression at various points within the reaction chamber flow channel is:

[0019]

[0020] in, d 1 represents the thickness of the dielectric barrier layer; d 2 represents the thickness of the wavy discharge electrode; d g This is the gap for discharge; e g The relative permittivity of the dielectric barrier layer; e 1 represents the relative permittivity of the wastewater; U The magnitude of the voltage output by the plasma power supply; d It is the distance from any point in the reaction chamber flow channel to the positive electrode, that is, the wavy discharge electrode connected to the live wire of the plasma power supply.

[0021] Furthermore, the microfluidic chip includes a liquid inlet, an air inlet, a flow-focusing microbubble generation structure, a discharge reaction chamber, and a liquid outlet; the flow-focusing microbubble generation structure includes an air inlet channel, a first liquid inlet channel, a second liquid inlet channel, a gas-liquid cross channel, and a bubble flow output port; the first end of the first liquid inlet channel and the first end of the second liquid inlet channel are coupled to the liquid inlet, the first end of the air inlet channel is connected to the air inlet, the second end of the first liquid inlet channel, the second end of the second liquid inlet channel, and the second end of the air inlet channel are coupled to the gas-liquid cross channel, the gas-liquid cross channel is connected to the discharge reaction chamber through the bubble flow output port, and the liquid outlet is connected to the discharge reaction chamber;

[0022] After being diverted through the inlet, the organic wastewater flows through the first and second inlet channels to the gas-liquid cross-flow channel. The discharge gas flows sequentially through the inlet and inlet channel to the gas-liquid cross-flow channel. The organic wastewater and discharge gas converge at the gas-liquid cross-flow channel to form a two-phase focusing flow field. The shear force generated during the liquid phase flow cuts the continuous gas phase into multiple bubbles. The size of these bubbles is calculated using the following formula:

[0023]

[0024] in, D The diameter of the generated bubble,w For the channel width, Q c and Q d These represent the liquid phase and gas phase flow rates, respectively. m and s These represent the dynamic viscosity and surface tension of the liquid phase, respectively.

[0025] Furthermore, organic wastewater and bubbles flow into the reaction chamber channel in the form of a bubble flow outlet. The expansion and contraction structure of the reaction chamber channel includes alternating contraction and expansion sections. In the contraction section of the reaction chamber channel, the cross-sectional area of ​​the channel is relatively reduced, resulting in an increase in the bubble flow velocity and a decrease in the internal pressure of the fluid. When the pressure drops to the saturated vapor pressure of the liquid phase, the non-condensable gases originally dissolved in the liquid phase rapidly escape and form a large number of cavitation bubbles through nucleation and expansion processes. In the expansion section of the reaction chamber channel, the cross-sectional area of ​​the channel is relatively increased, resulting in a decrease in the bubble flow velocity and an increase in the internal pressure of the fluid. This disrupts the equilibrium state of the cavitation bubbles, thereby triggering their collapse. The local high temperature and vibration effects generated during the collapse process can promote gas-liquid mixing to improve degradation efficiency. In addition, the cavitation bubbles generated by the decrease in fluid pressure and the bubbles originally contained in the bubble flow will interact, triggering aeration cavitation effect, further increasing the number of cavitation bubbles and the hydraulic cavitation intensity, thereby improving the gas-liquid mass transfer intensity.

[0026] Specifically, in the expanding structure, due to the local pressure drop below the saturated vapor pressure, bubbles and cavities are generated within the gas-liquid two-phase flow. This gas-liquid two-phase flow, containing bubbles and cavities, flows from the expanding structure into the adjacent contracting structure. At this point, the bubbles and cavities in the gas-liquid two-phase flow collapse as they flow into a relatively high-pressure area. This collapse process releases a large amount of energy, placing the gas-liquid two-phase flow in a relatively high-temperature and high-pressure environment, thereby further promoting the degradation of organic pollutants. The corrugated discharge electrode significantly improves the discharge uniformity of the gas-liquid two-phase flow. Preferably, the corrugated discharge electrode can be made using an aluminum plate electrode.

[0027] Furthermore, the bubble flow output port at the connection between the flow-focusing microbubble generation structure and the microfluidic chip has a transition structure to reduce stress concentration during the gas-liquid two-phase flow transport process and improve the structural strength of the flow-focusing microbubble generation structure.

[0028] Furthermore, the pollutant degradation device also includes a second plunger pump connected to the inlet and the collection tank, which is used to transport the treated wastewater in the collection tank, which still contains a certain concentration of organic pollutants, back to the microfluidic chip for multiple cycles of degradation.

[0029] Secondly, the present invention also provides a method for pollutant degradation using microchannel gas-liquid two-phase micro-discharge, employing the aforementioned microchannel gas-liquid two-phase micro-discharge organic wastewater degradation device, the method comprising the following steps:

[0030] Step 1: The wastewater in the organic wastewater tank is pumped to the inlet of the microfluidic chip by the first plunger pump;

[0031] Step 2: Gas is delivered to the air inlet of the microfluidic chip via a gas cylinder;

[0032] Step 3: Wastewater entering through the liquid inlet of the microfluidic chip flows into the first liquid inlet channel and the second liquid inlet channel respectively. Gas entering through the air inlet of the microfluidic chip flows into the air inlet channel. The wastewater in the first liquid inlet channel and the second liquid inlet channel will form a uniformly mixed gas-liquid two-phase flow in the flow focusing microbubble generation structure, which will combine with the gas in the air inlet channel in a mixed flow form of entrained focusing.

[0033] Step 4: Connect the wavy discharge electrode of the discharge reaction chamber to the plasma power supply and turn on the oscilloscope. Adjust the power of the plasma power supply by observing the oscilloscope.

[0034] Step 5: Open the bubble flow outlet so that the gas-liquid two-phase flow flows from the flow-focusing microbubble generation structure of the microchannel chip into the discharge reaction chamber. The organic wastewater is degraded through the superposition of three technologies: microbubble, cavitation phenomenon and dielectric barrier discharge.

[0035] Step Six: The degraded wastewater flows out from the outlet of the microfluidic chip and is eventually stored in a collection tank.

[0036] The beneficial effects of this invention are:

[0037] (1) The present invention improves the energy utilization rate of the discharge process by using an integrally installed dielectric barrier layer and a corrugated discharge electrode. Since the shape of the corrugated discharge electrode is perfectly matched with the shape of the reaction chamber flow channel, the effective discharge area of ​​the electrode is fully utilized, and all the discharge area is used for gas-liquid two-phase plasma in the microchannel, which significantly improves the energy utilization rate of the discharge process.

[0038] (2) This invention improves the heat dissipation of the electrode by using a wave-shaped discharge electrode with alternating discharge gap sizes, while ensuring the effective degradation of pollutants. The discharge gap of the electrode varies with the width of the expansion and contraction of the flow channel. At smaller discharge gaps, the reduction field strength is high and the degradation effect is good, but overheating is easily caused, which will damage the active material and affect the service life of the microfluidic chip. The discharge structure with alternating discharge gap sizes can ensure that the discharge area has a sufficiently high electric field strength and expand the heat dissipation area of ​​the electrode, effectively avoiding electrode overheating.

[0039] (3) This invention utilizes the shearing action of the liquid phase on the gas-liquid flow channel cross structure of the flow-focusing microbubble generation structure to generate microbubbles, thereby achieving thorough mixing of the gas and liquid phases. The microfluidic chip diverts the input organic wastewater, and the two streams of liquid shear the gas at the cross junction of the microfluidic chip, forming a gas-liquid two-phase flow with a high mixing ratio; at the same time, the output port of the cross junction has a smooth transition, which reduces the stress concentration of the gas-liquid two-phase flow on the microfluidic chip and improves the stability of the microfluidic chip structure.

[0040] (4) This invention achieves gas-liquid two-phase micro-discharge by delivering a fixed ratio of wastewater and air into the microfluidic chip, thereby improving the degradation effect and energy utilization rate. In the pure gas-phase discharge process commonly used in the prior art, a large number of short-half-lived active substances do not have enough time to react with pollutant molecules; while in the gas-liquid two-phase discharge process used in this invention, due to the full contact between the gas and liquid phases, all active substances can react with pollutant molecules immediately after being generated, avoiding the waste of active substances, thus resulting in better degradation effect and higher energy utilization rate.

[0041] (5) This invention uses a multi-stage expansion and contraction channel structure to induce a hydraulic cavitation effect, thereby significantly improving the gas-liquid mass transfer effect in the gas-liquid two-phase flow and thus improving the degradation effect of organic wastewater. When the gas-liquid two-phase flow enters the contraction channel, the flow velocity of the gas-liquid two-phase flow increases and the pressure decreases. When the local pressure is lower than its saturated vapor pressure, cavitation bubbles will be generated inside the gas-liquid two-phase flow. When the cavitation bubbles enter the expansion channel, the high pressure will cause the bubbles or cavities to collapse suddenly. This process will release a large amount of energy, resulting in extremely high pressure and temperature, which improves the degradation rate of organic pollutants.

[0042] The organic wastewater degradation device designed in this invention, which is based on microfluidic gas-liquid two-phase micro-discharge, firstly improves the gas-liquid mixing effect of wastewater and air through the cross-junction of the microfluidic chip, and then, through the expansion and contraction structure of the microfluidic chip reaction chamber and the electrode discharge effect, with the help of the dual effects of cavitation and plasma, it can ultimately significantly degrade organic pollutants in wastewater. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of an organic wastewater degradation device with microchannel gas-liquid two-phase micro-discharge in one embodiment of the present invention.

[0044] Figure 2 This is a schematic diagram of the structure of a microchannel chip in one embodiment of the present invention.

[0045] Figure 3 This is a schematic diagram of the structure of the hybrid flow channel group in a microfluidic chip according to one embodiment of the present invention.

[0046] Figure 4 This is a schematic diagram of the discharge reaction chamber in a microfluidic chip according to one embodiment of the present invention.

[0047] In the diagram, 1. Organic wastewater tank; 2. First plunger pump; 3. Microfluidic chip; 4. Gas tank; 5. Collection tank; 6. Plasma power supply; 7. Oscilloscope; 8. Second plunger pump; 31. Liquid inlet; 32. Air inlet; 33. Flow-focused microbubble generation structure; 34. Discharge reaction chamber; 343. Corrugated discharge electrode; 35. Liquid outlet; 331. Air inlet channel; 332. First liquid inlet channel; 333. Second liquid inlet channel; 334. Gas-liquid cross channel; 335. Bubble flow outlet; 341. Reaction chamber channel; 342. Dielectric barrier layer. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] In this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0050] In this invention, the terms "first" and "second" are used only to distinguish similar components / parts in different positions or with different characteristics, and have no other limiting meaning; "upper" refers to the direction in which each component is away from the ground, and "lower" refers to the direction in which each component is away from the ground.

[0051] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0052] Example 1

[0053] like Figure 1-Figure 4 As shown, the present invention provides a microfluidic gas-liquid two-phase micro-discharge organic wastewater degradation device, comprising:

[0054] Organic wastewater tank 1 is used to store wastewater containing organic pollutants, which is the target object that needs to be degraded.

[0055] The first plunger pump 2 is connected to the organic wastewater tank 1;

[0056] Gas tank 4 is used to store and provide discharge gas for the gas-liquid two-phase micro-discharge process. The discharge gas can be ozone, oxygen or air.

[0057] Collection tank 5 is used to store degraded organic wastewater;

[0058] The microfluidic chip 3 is coupled to the organic wastewater tank 1, the first plunger pump 2, the gas tank 4, and the collection tank 5. The microfluidic chip 3 is configured with a mixing channel assembly and a discharge reaction chamber 34 connecting the mixing channel assembly and the collection tank 5. The discharge reaction chamber 34 includes a reaction chamber channel 341, a dielectric barrier layer 342, and a corrugated discharge electrode 343. The reaction chamber channel 341 is a multi-segment continuous expansion and contraction structure with corrugated walls. The dielectric barrier layer 342 and the corrugated discharge electrode 343 are corrugated thin plates with identical shape and dimensions, and are tightly bonded together to form an integrated corrugated structure. The shape of the corrugated structure is similar to... The wall shape of the reaction chamber channel 341 is perfectly matched. The discharge spacing of the wavy discharge electrode 343 increases as the reaction chamber channel 341 expands and decreases as it contracts, forming a discharge structure with alternating spacing sizes. This arrangement allows the effective discharge area of ​​the electrode to be fully utilized, and all the discharge area is used for gas-liquid two-phase plasma ionization in the microchannel, greatly improving the energy utilization rate of the device. Furthermore, the discharge spacing of the wavy discharge electrode increases as the reaction chamber channel expands and decreases as it contracts, forming a discharge structure with alternating spacing sizes, which can ensure that the discharge area has a sufficiently high electric field strength and also avoid electrode overheating.

[0059] Plasma power supply 6 is connected to the discharge reaction chamber 34 of the microfluidic chip 3 and provides electrical energy for the plasma discharge process; and

[0060] Oscilloscope 7 is connected to the plasma power supply 6 and is used to detect the plasma discharge power in real time.

[0061] Organic wastewater is pumped into the microfluidic chip 3 by the first plunger pump 2, where a plasma degradation reaction occurs in the discharge reaction chamber 34 inside the microfluidic chip 3.

[0062] Plasma power supply 6 is connected to the discharge reaction chamber 34 of the microfluidic chip 3 and provides electrical energy; and

[0063] An oscilloscope 7 is connected to the plasma power supply 6 to observe the electrical power released by the plasma power supply 6, thereby adjusting the electrical power released by the plasma power supply 6.

[0064] The microfluidic chip 3 includes a liquid inlet 31, an air inlet 32, a flow-focusing microbubble generation structure 33, a discharge reaction chamber 34, and a liquid outlet 35. The flow-focusing microbubble generation structure 33 includes an air inlet channel 331, a first liquid inlet channel 332, a second liquid inlet channel 333, a gas-liquid cross channel 334, and a bubble flow outlet 335. The first end of the first liquid inlet channel 332 and the first end of the second liquid inlet channel 333 are coupled to the liquid inlet 31. The first end of the air inlet channel 331 is connected to the air inlet 32. The second ends of the first liquid inlet channel 332, the second liquid inlet channel 333, and the second end of the air inlet channel 331 are coupled to the gas-liquid cross channel 334. The gas-liquid cross channel 334 is connected to the discharge reaction chamber 34 through the bubble flow outlet 335, and the liquid outlet 35 is connected to the discharge reaction chamber 34.

[0065] After being diverted through inlet 31, the organic wastewater flows through the first inlet channel 332 and the second inlet channel 333 to the gas-liquid cross channel 334; the discharge gas flows sequentially through inlet 32 ​​and inlet channel 331 to the gas-liquid cross channel 334; the organic wastewater and discharge gas converge at the gas-liquid cross channel 334 to form a gas-liquid two-phase focusing flow field. The shear force generated during the liquid phase flow cuts the continuous gas phase into multiple bubbles, and the size of the bubbles is calculated using the following formula:

[0066]

[0067] in, D The diameter of the generated bubble, w For the channel width, Q c and Q d These represent the liquid phase and gas phase flow rates, respectively. m and s These represent the dynamic viscosity and surface tension of the liquid phase, respectively.

[0068] Organic wastewater and bubbles flow into the reaction chamber channel 341 through the bubble flow outlet 335 in the form of a bubble flow. The expansion and contraction structure of the reaction chamber channel 341 includes alternating contraction and expansion sections. In the contraction section of the reaction chamber channel 341, the cross-sectional area of ​​the channel is relatively reduced, resulting in an increase in the bubble flow velocity and a decrease in the internal pressure of the fluid. When the pressure drops to the saturated vapor pressure of the liquid phase, the non-condensable gases originally dissolved in the liquid phase rapidly escape and form a large number of cavitation bubbles through nucleation and expansion processes. In the expansion section of the reaction chamber channel 341, the cross-sectional area of ​​the channel is relatively increased, resulting in a decrease in the bubble flow velocity and an increase in the internal pressure of the fluid. This disrupts the equilibrium state of the cavitation bubbles, thereby triggering the collapse of the cavitation bubbles. The local high temperature and vibration effects generated during the collapse process can promote gas-liquid mixing to improve degradation efficiency. In addition, the cavitation bubbles generated by the decrease in fluid pressure and the bubbles originally contained in the bubble flow will interact to trigger a ventilation cavitation effect, further increasing the number of cavitation bubbles and the hydraulic cavitation intensity, thereby improving the gas-liquid mass transfer intensity.

[0069] The bubble flow output port 335 at the connection between the flow-focusing microbubble generation structure 33 and the microfluidic chip 3 has a transition structure to reduce stress concentration during the gas-liquid two-phase flow transport process and improve the structural strength of the flow-focusing microbubble generation structure.

[0070] The pollutant degradation device also includes a second plunger pump 8 connected to the inlet 31 and the collection tank 5, which is used to transport the treated wastewater in the collection tank 5, which still contains a certain concentration of organic pollutants, back to the microchannel chip 3 for multiple cycles of degradation.

[0071] Example 2

[0072] This embodiment demonstrates the derivation of the expression for the reduced field strength at various points in the reaction chamber flow channel 341 described in Embodiment 1. The dielectric barrier layer 342 is made of a ceramic layer with a high dielectric constant. Since the wavy discharge electrode 343 and the dielectric barrier layer 342 are closely attached, the electric field strength generated by the wavy discharge electrode 343 is related to the external dimensions of the dielectric barrier layer 342 and the wavy discharge electrode 343.

[0073] The gas-liquid mixing effect in the microfluidic chip 3 can be analyzed using the capillary number. The capillary number represents the relative importance of the viscous force and surface tension of the gas and liquid phases. The smaller the capillary number, the better the mixing effect of the gas-liquid two-phase flow. The value of the capillary number falls between 0.01 and 10. The mathematical expression of the capillary number is as follows:

[0074]

[0075] in, Capillary number The viscosity of a continuous liquid phase. This represents the average velocity of the continuous liquid phase.

[0076] Furthermore, to improve the degradation rate of the gas-liquid two-phase flow in the discharge reaction chamber 34 of the microfluidic chip 3, it is necessary to reduce the size of the air bubbles in the gas-liquid two-phase flow and increase the number of bubbles. The mathematical expression for bubble size is:

[0077]

[0078] in, For bubble size, The dimensions of the liquid inlet 31 and the air inlet 32, For the volumetric flow rate of organic wastewater, For air volumetric flow rate, - - It is a constant related to the microchannel size.

[0079] The mathematical expression for bubble frequency is:

[0080]

[0081] in, For the frequency of bubble generation, - - This is a constant related to the microchannel size. Based on multiple experimental tests... At this time, small and numerous bubbles can be generated. The flow rate of organic wastewater is 300 μL / min, and the flow rate of air is 100 μL / min.

[0082] Furthermore, the discharge reaction chamber 34 in the microfluidic chip 3 will perform dielectric barrier discharge based on the cavitation effect of the gas-liquid two-phase flow. To ensure uniform discharge of the gas-liquid two-phase flow in the discharge reaction chamber 34, a corrugated plate electrode with the same structure as the reaction chamber 34 is designed. The electric field expression at various points in the discharge reaction chamber 34 is as follows:

[0083]

[0084] in, d 1 represents the thickness of the dielectric barrier layer; d 2 represents the thickness of the wavy discharge electrode; d g This is the gap for discharge; e g The relative permittivity of the dielectric barrier layer; e 1 represents the relative permittivity of the wastewater; U The magnitude of the voltage output by the plasma power supply; dIt is the distance from any point in the reaction chamber flow channel to the positive electrode, that is, the wavy discharge electrode 343 connected to the live wire of the plasma power supply.

[0085] Furthermore, during the micro-discharge process in the discharge reaction chamber 34, electrons gain sufficient energy to excite oxygen into oxygen atoms, thereby generating ozone bubbles. The strong oxidizing effect of ozone can effectively decompose organic pollutants in wastewater by breaking carbon-carbon double bonds and other components in organic matter, thus decomposing them.

[0086] Furthermore, the air inside the microbubbles in the discharge reaction chamber 34 undergoes an ionization reaction to generate ozone. The microbubbles can effectively improve the gas-liquid mass transfer intensity between ozone and wastewater, thereby promoting the hydrolysis of ozone to generate a large number of hydroxyl radicals. The oxidation potential of hydroxyl radicals is 2.8 eV, significantly higher than that of ozone (2.07 eV). Furthermore, the reaction rate between hydroxyl radicals and organic pollutant molecules is 3-6 orders of magnitude higher than that between ozone and organic pollutant molecules, thus significantly enhancing the degradation effect. The generation process is as follows:

[0087]

[0088]

[0089]

[0090]

[0091]

[0092] Furthermore, the gas-liquid two-phase flow containing organic pollutants undergoes a double effect of cavitation and discharge, resulting in the significant degradation of the organic pollutants. The treated gas-liquid two-phase flow then flows into treatment tank 5.

[0093] Furthermore, when the concentration of organic pollutants in the untreated organic wastewater is too high in the initial condition, and a high concentration still exists after one round of degradation, the wastewater in the treatment tank 5 is re-transported to the microfluidic chip 3 by the plunger pump 2 to carry out multiple rounds of degradation in order to improve the degradation rate of organic pollutants.

[0094] Example 3

[0095] This invention also provides a method for pollutant degradation using microchannel gas-liquid two-phase micro-discharge, applying the microchannel gas-liquid two-phase micro-discharge organic wastewater degradation device described in Examples 1 and 2. The method includes the following steps:

[0096] Step 1: The wastewater in the organic wastewater tank 1 is pumped to the inlet 31 of the microchannel chip 3 by the first plunger pump 2;

[0097] Step 2: Gas is delivered to the air inlet 32 ​​of the microfluidic chip 3 through the gas tank 4;

[0098] Step 3: Wastewater entering through the inlet 31 of the microfluidic chip 3 flows into the first inlet channel 332 and the second inlet channel 333 respectively. Gas entering through the air inlet of the microfluidic chip flows into the air inlet channel 331. The wastewater in the first inlet channel 332 and the second inlet channel 333 will form a uniformly mixed gas-liquid two-phase flow in the flow focusing microbubble generation structure 33, which will combine with the gas in the air inlet channel 331 in a mixed flow form of entrained focusing.

[0099] Step 4: Connect the wavy discharge electrode 343 of the discharge reaction chamber 34 to the plasma power supply 6 and turn on the oscilloscope 7. Adjust the power of the plasma power supply 6 by observing the oscilloscope 7.

[0100] Step 5: Open the bubble flow outlet 335 so that the gas-liquid two-phase flow flows from the flow focusing microbubble generation structure 33 of the microchannel chip 3 and the bubble flow outlet 335 into the discharge reaction chamber 34. The organic wastewater is degraded through the superposition of three technologies: microbubble, cavitation phenomenon and dielectric barrier discharge.

[0101] Step 6: The degraded wastewater flows out from the outlet 35 of the microfluidic chip 3 and is eventually stored in the collection tank 5. The treated wastewater in the collection tank 5, which still contains some organic pollutants, can be transported back to the microfluidic chip 3 for multiple cycles of degradation through the second plunger pump 8.

[0102] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A microfluidic gas-liquid two-phase micro-discharge organic wastewater degradation device, characterized in that, include: Organic wastewater tank (1), used to store organic wastewater; The first plunger pump (2) is connected to the organic wastewater tank (1); Gas tank (4) is used to store and provide discharge gas for the gas-liquid two-phase micro-discharge process; Collection tank (5) is used to store degraded organic wastewater; The microfluidic chip (3) is coupled to the organic wastewater tank (1), the first plunger pump (2), the gas tank (4), and the collection tank (5). The microfluidic chip (3) is equipped with a mixing channel group and a discharge reaction chamber (34) connecting the mixing channel group and the collection tank (5). The discharge reaction chamber (34) includes a reaction chamber channel (341), a dielectric barrier layer (342), and a wave-shaped discharge electrode (343). The reaction chamber channel (341) is a multi-segment continuous expansion and contraction structure with a wave-shaped wall. The dielectric barrier layer (342) and the wave-shaped discharge electrode (343) The two are corrugated thin plates with the same shape and size, and are closely attached to form an integrated corrugated structure. The effective discharge area of ​​the corrugated discharge electrode (343) is fully utilized. All discharge areas are used for gas-liquid two-phase plasma in the microchannel, which greatly improves the energy utilization rate of the device. The shape of the corrugated structure is completely matched with the wall shape of the reaction chamber channel (341). The discharge spacing of the corrugated discharge electrode (343) increases as the spacing of the reaction chamber channel (341) expands and decreases as the spacing of the reaction chamber channel (341) contracts, forming a discharge structure with alternating spacing sizes. Plasma power supply (6) is connected to the discharge reaction chamber (34) of the microfluidic chip (3) and provides electrical energy for the plasma discharge process; and An oscilloscope (7) is connected to the plasma power supply (6) to detect the plasma discharge power in real time. Organic wastewater is pumped into the microfluidic chip (3) by the first plunger pump (2), and a plasma degradation reaction occurs in the discharge reaction chamber (34) inside the microfluidic chip (3); The microfluidic chip (3) includes a liquid inlet (31), an air inlet (32), a flow-focusing microbubble generation structure (33), a discharge reaction chamber (34), and a liquid outlet (35); the flow-focusing microbubble generation structure (33) includes an air inlet channel (331), a first liquid inlet channel (332), a second liquid inlet channel (333), a gas-liquid cross channel (334), and a bubble flow outlet (335); the first end of the first liquid inlet channel (332) and the second liquid inlet... The first end of the inlet channel (333) is coupled to the liquid inlet (31), the first end of the air inlet channel (331) is connected to the air inlet (32), the second end of the first liquid inlet channel (332), the second end of the second liquid inlet channel (333), and the second end of the air inlet channel (331) are coupled to the gas-liquid cross channel (334), the gas-liquid cross channel (334) is connected to the discharge reaction chamber (34) through the bubble flow outlet (335), and the liquid outlet (35) is connected to the discharge reaction chamber (34). After the organic wastewater is diverted through the inlet (31), it flows through the first inlet channel (332) and the second inlet channel (333) to the gas-liquid cross channel (334); the discharge gas flows through the inlet (32) and the inlet channel (331) to the gas-liquid cross channel (334); the organic wastewater and the discharge gas converge at the gas-liquid cross channel (334) to form a gas-liquid two-phase focusing flow field, and the shear force generated when the liquid phase flows cuts the continuous gas phase into multiple bubbles.

2. The organic wastewater degradation device based on microfluidic gas-liquid two-phase micro-discharge according to claim 1, characterized in that, Organic wastewater and bubbles flow into the reaction chamber channel (341) through the bubble flow outlet (335) in the form of a bubble flow. The expansion and contraction structure of the reaction chamber channel (341) includes alternating contraction and expansion sections. In the contraction section of the reaction chamber channel (341), the cross-sectional area of ​​the channel is relatively reduced, which increases the flow velocity of the bubble flow and reduces the internal pressure of the fluid. When the pressure drops to the saturated vapor pressure of the liquid phase, the non-condensable gases originally dissolved in the liquid phase escape rapidly and form a large number of cavitation bubbles through nucleation and expansion processes. In the expansion section of the reaction chamber channel (341), the cross-sectional area of ​​the channel is relatively increased, which reduces the flow velocity of the bubble flow and increases the internal pressure of the fluid, which disrupts the equilibrium state of the cavitation bubbles and causes them to collapse. The local high temperature and vibration effect generated during the collapse process can promote gas-liquid mixing to improve degradation efficiency. In addition, the cavitation bubbles generated by the decrease in fluid pressure and the bubbles originally contained in the bubble flow will interact to induce aeration cavitation effect, further increasing the number of cavitation bubbles and the hydraulic cavitation intensity, thereby improving the gas-liquid mass transfer intensity.

3. The organic wastewater degradation device based on microchannel gas-liquid two-phase micro-discharge according to claim 2, characterized in that, The bubble flow outlet (335) at the connection between the flow-focusing microbubble generation structure (33) and the microfluidic chip (3) has a transition structure to reduce stress concentration during the gas-liquid two-phase flow transport process and improve the structural strength of the flow-focusing microbubble generation structure.

4. The microfluidic gas-liquid two-phase micro-discharge organic wastewater degradation device according to claim 3, characterized in that, The organic wastewater degradation device also includes a second plunger pump (8) connected to the inlet (31) and the collection tank (5) to transport the treated wastewater in the collection tank (5) that still contains a certain concentration of organic pollutants to the microchannel chip (3) for multiple cycles of degradation.

5. A method for pollutant degradation via microchannel gas-liquid two-phase micro-discharge, using the microchannel gas-liquid two-phase micro-discharge organic wastewater degradation device as described in claim 4, the method comprising the following steps: Step 1: The wastewater in the organic wastewater tank (1) is pumped to the inlet (31) of the microfluidic chip (3) by the first plunger pump (2). Step 2: Gas is delivered to the air inlet (32) of the microfluidic chip (3) through the gas tank (4); Step 3: Wastewater entering through the inlet (31) of the microfluidic chip (3) flows into the first inlet channel (332) and the second inlet channel (333) respectively. Gas entering through the air inlet (32) of the microfluidic chip (3) flows into the air inlet channel (331). The wastewater in the first inlet channel (332) and the second inlet channel (333) forms a uniformly mixed bubble flow in the flow focusing microbubble generation structure (33) with the gas in the air inlet channel (331) in a mixed flow form of entrained focusing. Step 4: Connect the wave-shaped discharge electrode (343) of the discharge reaction chamber (34) to the plasma power supply (6) and turn on the oscilloscope (7). Adjust the power of the plasma power supply (6) by observing the oscilloscope (7). Step 5: Open the bubble flow outlet (335) so that the gas-liquid two-phase flow flows from the flow-focusing microbubble generation structure (33) of the microchannel chip (3) into the discharge reaction chamber (34). The organic wastewater is degraded by the superposition of three technologies: microbubble, cavitation phenomenon and dielectric barrier discharge. Step 6: The degraded wastewater flows out from the outlet (35) of the microfluidic chip (3) and is eventually stored in the collection tank (5).

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