Jet plasma nitrogen fixation device and method based on nanosecond pulse spark discharge

Abstract

The present invention provides a jet plasma nitrogen fixation device based on nanosecond pulsed spark discharge, comprising a reaction vessel and a plasma generator. The reaction vessel is provided with a liquid inlet and a liquid outlet. The liquid inlet is connected to a circulation pump, through which a reaction liquid is introduced into the reaction vessel. The liquid outlet is connected to a collection container. The plasma generator includes a tubular plasma generating chamber fixed to the top of the reaction vessel. The top of the plasma generating chamber is provided with a gas inlet for introducing a reaction gas into the plasma generating chamber. The reaction vessel is also provided with an exhaust gas outlet. The nitrogen fixation device of the present invention has no obstructing medium and directly breaks down the gas, resulting in a low discharge difficulty. The resulting spark discharge has a high temperature, which is more conducive to nitrogen fixation.

Description

Technical Field

[0001] The present invention relates to the technical field of nitrogen fixation, and in particular to a jet plasma nitrogen fixation device and method based on nanosecond pulse spark discharge. Background Art

[0002] Nitrogen is one of the most essential elements for plant and animal life. Although atmospheric nitrogen accounts for as much as 79%, due to the high N≡N bond energy, plants and animals cannot directly absorb and utilize nitrogen dioxide (N≡N) from the air. Instead, they must convert free nitrogen into nitrogen-containing compounds, such as ammonia, nitrogen oxides, and ammonium salts. Therefore, nitrogen fixation is necessary to convert N≡N into simpler nitrogen-containing compounds, such as ammonia and nitrogen oxides. Only a few microorganisms or lightning can fix nitrogen in nature. However, with the rapid growth of the human population, natural nitrogen fixation is far from meeting demand, making artificial nitrogen fixation the primary source.

[0003] The current mainstream method of industrial nitrogen fixation is the Haber process, which can produce 130 million tons of ammonia annually. Fertilizer production based on this process feeds 40% of the world's population. However, its production conditions are harsh and energy consumption is high. It requires the use of metal catalysts to synthesize ammonia from N2 and H2 under high temperature and high pressure conditions. It relies heavily on non-renewable fossil fuels to prepare raw material H2 as an energy provider, and emits a large amount of greenhouse gas CO2, which is not in line with the concept of low-carbon, environmental protection and sustainability.

[0004] Plasma is an efficient means of molecular activation. In a plasma environment, many physical and chemical reactions that are difficult to carry out under conventional conditions can occur. Using plasma technology to activate N2 for nitrogen fixation does not require high temperature, high pressure and catalysts. It is a potential green nitrogen fixation technology. Among them, plasma oxidation nitrogen fixation technology directly uses N2 and O2 to react to generate nitrogen oxides (NO x ), air can be directly used as raw material, which has a wide source and is easy to collect. Greenhouse gas emissions can be avoided during the nitrogen fixation process, and renewable energy can be effectively used for distributed and small-batch production. It has positive significance for reducing carbon emissions and promoting "carbon neutrality", and is an important development trend of plasma nitrogen fixation technology.

[0005] The most energy-efficient pathway for nitrogen oxide formation during plasma oxidation and nitrogen fixation is the Zeldocivh mechanism, which promotes vibrational excitation. This mechanism involves the reaction of nitrogen and oxygen molecules in their vibrational excited states, along with reactive nitrogen and oxygen atoms, to form nitric oxide, which in turn generates nitrogen dioxide. Therefore, the plasma electric field strength must be low to maximize the vibrational excitation process, and the plasma gas temperature must be high enough (greater than 1000 K) during the discharge to ensure that nitrogen and oxygen molecules break apart to produce reactive atoms.

[0006] The existing plasma nitrogen fixation methods include pure gas phase nitrogen fixation, pure liquid phase nitrogen fixation, and gas-liquid two-phase nitrogen fixation. Commonly used nitrogen fixation devices include sliding arc nitrogen fixation, single / multi-needle plate nitrogen fixation, and jet nitrogen fixation.

[0007] The sliding arc nitrogen fixation device, such as patent CN205133431U, uses a sliding arc discharge device to generate plasma to excite air and produce NO. X The active groups are then mixed with water to form liquid nitrogen fertilizer. This not only provides nutritional supplements for crops and improves nitrogen absorption, but also reduces costs while killing bacteria that harm plants and reducing the risk of bacterial infection. Liquid nitrogen fertilizer active substances are easily decomposed, effectively reducing environmental pollution. However, sliding arc nitrogen fixation devices suffer from unstable discharge and can only fix nitrogen within a single plane, limiting the processing area. Furthermore, reverse reactions occur, reducing product concentration, requiring large amounts of energy, and resulting in low nitrogen fixation energy efficiency.

[0008] Dielectric barrier discharge nitrogen fixation devices, such as CN202010211275.5, are based on liquid film dielectric barrier discharge devices to generate low-temperature plasma. Using nitrogen and water as raw materials, they directly react to generate nitrate ions and ammonium ions. Nitrogen fixation is achieved under mild conditions without the use of catalysts and hydrogen. It is low-carbon and environmentally friendly. The device has a simple structure, small size, and easy-to-obtain raw materials at low cost. It achieves rapid nitrogen fixation, small-scale distributed production, fast reaction speed, and high energy efficiency. For example, patent CN110327749A uses corona dielectric barrier synergistic discharge, with a low starting discharge voltage, and uses the exhaust gas treatment device to degrade NO X Using dielectric barrier discharge as a gas raw material, it simultaneously purifies the air and achieves nitrogen fixation, which is environmentally friendly and has high nitrogen fixation efficiency. However, the discharge gap of dielectric barrier discharge is small, and the treatment area is limited, which cannot achieve large-scale nitrogen fixation. The required starting discharge voltage is high, resulting in large energy loss, low energy efficiency and low synthesis rate.

[0009] The jet nitrogen fixation device, such as patent CN201911008208.7, combines electrochemistry and plasma, uses a small electrolytic cell, first passes air or a mixture of nitrogen and oxygen into the reaction device to generate a stable jet plasma, and then continuously discharges for 10 minutes before passing the reaction liquid into the electrolytic cell. After a period of reaction, NH4 is generated. +, which is environmentally friendly and improves the efficiency and rate of ammonia synthesis. For example, patent CN201721644510.8 places a high-voltage electrode in a jet discharge cavity and connects it to a high-voltage power supply. The high-voltage electrode is fixed by an insulator fixed above the liquid surface and is connected to a booster fan. The booster fan blows air into the jet discharge cavity through the air intake duct. The active particle atmosphere generated can fully react with the liquid phase, with a large contact area and high nitrogen fixation efficiency. For example, patent CN202010382065.2 uses a magnetic cyclonic jet method to generate plasma. The nitrogen oxides generated by the plasma are absorbed in a double water cycle in the gas absorption device and the absorption liquid receiving device, and are combined with the free ammonia in the organic fertilizer to form ammonium salts, thereby improving the properties of the fertilizer and converting nitrogen oxides and ammonia that cannot be absorbed and utilized by crops into absorbable ammonium nitrate, thereby enhancing the fertility of the organic fertilizer. The device is simple and convenient, with low emissions, and energy is provided by solar energy, which is in line with sustainable development. However, the traditional single jet discharge is weak and the processing capacity is very limited. The array jet can meet the needs of large-area processing, but the array jet stability is easily affected and the control is complicated. It is more common to fix nitrogen above the liquid phase, and the size of the nitrogen below the liquid phase is very small.

[0010] Compared with other discharge forms such as dielectric barrier discharge, spark discharge uses bare electrodes, has low discharge breakdown voltage and low electric field strength, which can well promote vibration excitation reactions in plasma; at the same time, the gas temperature of the plasma during the duration of the spark discharge is often between 1000-3000 K, which can effectively ensure the generation of active nitrogen and oxygen atoms. Therefore, the use of spark discharge can greatly improve the yield and energy efficiency of nitrogen oxides. However, the relatively high gas temperature will reduce the layout of the vibrational excited state through vibration-translational relaxation (i.e., the collision between the vibrational excited state and the ground state molecule). Therefore, it is necessary to quickly cool the plasma in the discharge afterglow stage to maintain high vibration excitation of nitrogen oxide molecules. Based on this, the present invention designs a jet plasma nitrogen fixation device and method based on nanosecond pulsed spark discharge, and combines it with gas-liquid discharge, using plasma-liquid interaction to quickly cool the plasma afterglow area outside the jet nozzle, and at the same time directly dissolve the generated nitrogen oxides in the liquid phase to form NO3 - 、NO2 - The ionic form exists in the liquid phase, promoting the formation reaction of nitrogen oxides in the gas phase, and the resulting nitrogen-rich solution can be directly used in application scenarios such as agricultural drip irrigation systems. Summary of the Invention

[0011] The object of the present invention is to provide a jet plasma nitrogen fixation device and method based on nanosecond pulsed spark discharge to solve the above technical problems.

[0012] To achieve the above objectives, the present invention provides a jet plasma nitrogen fixation device and method based on nanosecond pulsed spark discharge.

[0013] A jet plasma nitrogen fixation device based on nanosecond pulse spark discharge, comprising a reaction vessel and a plasma generating device;

[0014] The reaction vessel is provided with a liquid inlet and a liquid outlet; the liquid inlet is connected to a circulation pump; the reaction liquid is introduced into the reaction vessel through the circulation pump; the liquid outlet is connected to a collection container;

[0015] The plasma generating device includes a tubular plasma generating chamber; the plasma generating chamber is fixed on the top of the reaction vessel; a gas inlet is provided on the top of the plasma generating chamber; the gas inlet is used to introduce reaction gas into the plasma generating chamber; an exhaust gas outlet is also provided on the reaction vessel, and the exhaust gas outlet is connected to the exhaust gas absorption detection device; a flow equalizing plate is provided in the plasma generating chamber; an alumina ceramic ring is detachably installed in the plasma generating chamber below the flow equalizing plate; the alumina ceramic ring consists of an outer ring body and an inner ring body; electrode plates are provided on the top and bottom of the inner ring body; one of them is a high-voltage electrode plate and the other is a ground electrode plate; both the high-voltage electrode plate and the ground electrode plate are provided with openings for the reaction gas to pass through; the high-voltage electrode plate is connected to a nanosecond pulse power supply; and the ground electrode plate is grounded.

[0016] Furthermore, the plasma generating chamber is made of high temperature resistant material, preferably nylon or polytetrafluoroethylene.

[0017] Furthermore, the gas inlet is connected to a gas flow meter.

[0018] Furthermore, the plasma generating chamber is composed of an upper sleeve and a lower sleeve; the lower sleeve is sleeved on the bottom of the upper sleeve, and a ring-shaped flange is provided on the inner side of the bottom of the lower sleeve; the alumina ceramic ring is clamped between the flange and the upper sleeve.

[0019] Furthermore, the lower casing is provided with a high-voltage line inlet and a ground line inlet.

[0020] Furthermore, the exhaust gas absorption detection device includes a cold trap and a detection system, and the exhaust gas enters the detection system after being absorbed by the cold trap.

[0021] Preferably, the aperture of the openings on the high-voltage electrode plate is 1-1.5 mm; the number of openings on the high-voltage electrode plate is 1-17.

[0022] Preferably, the diameter of the openings on the ground electrode plate is 0.6-1 mm, and the number of openings on the ground electrode plate is 1-17.

[0023] Preferably, the openings on the high-voltage electrode plate or the ground electrode plate are asymmetrically arranged.

[0024] Preferably, the inner ring body of the alumina ceramic ring has a thickness of 1 to 6 mm.

[0025] The jet plasma nitrogen fixation method based on nanosecond pulsed spark discharge includes:

[0026] S1: The reaction liquid is continuously introduced into the reaction vessel through a circulation pump, and the reaction liquid flows out through the liquid outlet; the liquid level of the reaction liquid is maintained in one of the following two states:

[0027] 1) The liquid level is 3~5mm below the bottom of the lowest electrode plate;

[0028] 2) The liquid level does not exceed the bottom electrode plate;

[0029] S2: introducing reaction gas into the plasma generating chamber through the gas inlet;

[0030] S3: Turning on the nanosecond pulse power switch generates a spark discharge between the high-voltage electrode plate and the ground electrode plate. The reaction gas generates plasma in the spark discharge area. The plasma flows with the reaction gas, forms a jet or bubble through the opening on the bottom electrode plate, enters the reaction liquid, and reacts with the reaction liquid to form nitrate and nitrite, which dissolve in the reaction liquid.

[0031] S4: After the reaction is completed, turn off the nano pulse power supply and circulation pump, and stop introducing the reaction gas.

[0032] Furthermore, the reaction gas is a mixture of nitrogen and oxygen, air or pure nitrogen.

[0033] Preferably, the flow rate of the reaction gas is 3-8 L / min.

[0034] Preferably, the reaction liquid is water.

[0035] Preferably, the nanosecond pulse power supply voltage is 9 kV, the frequency is 2000 Hz, the pulse width is 500 ns, and the rising edge and the falling edge are both 50 ns.

[0036] Beneficial effects:

[0037] 1. Nitrogen fixation devices utilize no barrier dielectric, directly breaking down the gas. This reduces discharge difficulty, and the resulting spark discharge, with its high temperature, is particularly beneficial for nitrogen fixation. Compared to other discharge methods, such as dielectric barrier discharge, spark discharge utilizes bare electrodes, resulting in a low breakdown voltage and electric field strength, which effectively promotes vibrational excitation reactions in the plasma. During the duration of the spark discharge, the plasma gas temperature typically ranges from 1000 to 3000 K, effectively ensuring the generation of reactive nitrogen and oxygen atoms, significantly improving nitrogen oxide yield and energy efficiency.

[0038] 2. This device uses air, pure nitrogen or a mixture of nitrogen and oxygen as raw materials, with low pollution, no greenhouse gas emissions and low energy consumption.

[0039] 3. When the reaction liquid level exceeds the bottom electrode plate, dense small bubbles form at the bottom electrode plate, dividing the entire reaction zone into three parts: the gas phase, the gas-liquid mixed zone, and the liquid phase. First, gas discharge occurs in the gas phase, generating high-energy metastable particles. Driven by the airflow, these particles enter the gas-liquid mixed zone and react with water molecules. The products enter the liquid phase in the form of bubbles, forming the final product aqueous solution. This ensures plasma utilization while generating more plasma, greatly increasing the yield of nitrogen-containing compounds.

[0040] 4. The removable alumina ceramic ring allows for easy replacement of the high-voltage and ground electrode plates. By replacing alumina ceramic rings of varying specifications, the discharge gap between the high-voltage and ground electrode plates, i.e., the thickness of the inner ring, can be controlled. The relative position of the circular holes on the two plates can be controlled, thereby controlling the intensity and uniformity of the generated jet. The jet length can be easily controlled by the gas flow rate.

[0041] 5. The position of the nitrogen fixation device relative to the liquid phase can be changed. By controlling the composition of the reaction liquid, the main target product generated can be controlled to achieve multiple uses. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The invention discloses a jet plasma nitrogen fixation device based on nanosecond pulse spark discharge.

[0043] Figure 2 It is a structural schematic diagram of the plasma generating chamber of the present invention.

[0044] Figure 3 Schematic diagram of the structure of the alumina ceramic ring of the present invention.

[0045] Figure 4 Schematic diagram of the exhaust gas absorption detection device of the present invention.

[0046] Figures 5 to 10 Schematic diagram of the structure of high-voltage electrode plates or ground electrode plates with different numbers of holes and hole diameters of the present invention.

[0047] Figure 11 This is a current and voltage waveform diagram of Example 2 of the present invention.

[0048] Figure 12 This is a current and voltage waveform diagram of Example 3 of the present invention.

[0049] Figure 13 This is a current and voltage waveform diagram of Example 4 of the present invention.

[0050] Figure 14 This is a current and voltage waveform diagram of Example 5 of the present invention. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meanings understood by people with ordinary skills in the field to which the present invention belongs. The words "including" and similar words used in this article mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0052] In response to the problems existing in the prior art, embodiments of the present invention provide a jet plasma nitrogen fixation device and method based on nanosecond pulsed spark discharge.

[0053] Example 1

[0054] like Figures 1-3 As shown, the jet plasma nitrogen fixation device based on nanosecond pulsed spark discharge includes a reaction vessel 1 and a plasma generating device 2;

[0055] The reaction vessel 1 is provided with a liquid inlet 3 and a liquid outlet 4; the liquid inlet 3 is connected to a circulation pump; the reaction liquid is introduced into the reaction vessel 1 through the circulation pump; the liquid outlet 4 is connected to a collection container;

[0056] The plasma generator 2 includes a tubular plasma generating chamber 5, which is fixed to the top of the reaction vessel 1. A gas inlet 6 is provided at the top of the plasma generating chamber 5. The gas inlet 6 is used to introduce reactant gas into the plasma generating chamber 5. The reaction vessel 1 also has an exhaust gas outlet 7, which is connected to an exhaust gas absorption and detection device. A flow equalizing plate 8 is provided within the plasma generating chamber 5. An alumina ceramic ring 9 is removably mounted within the plasma generating chamber below the flow equalizing plate 8. The alumina ceramic ring 9 consists of an outer ring body 9-1 and an inner ring body 9-2. A high-voltage electrode plate 10 is mounted on the top of the inner ring body 9-2, and a ground electrode plate 11 is mounted on the bottom of the inner ring body 9-2. Both the high-voltage electrode plate 10 and the ground electrode plate 11 have openings for the reactant gas to pass through. The high-voltage electrode plate 10 is connected to a nanosecond pulse power supply, and the ground electrode plate 11 is grounded. The alumina ceramic ring prevents electrical creepage.

[0057] The plasma generating chamber 5 is made of high temperature resistant material, usually nylon or polytetrafluoroethylene.

[0058] The gas inlet 6 is connected to a gas flow meter.

[0059] The plasma generating chamber 5 is composed of an upper sleeve 5-1 and a lower sleeve 5-2; the lower sleeve 5-2 is sleeved on the bottom of the upper sleeve 5-1, and a ring-shaped flange is provided on the inner side of the bottom of the lower sleeve 5-2; the alumina ceramic ring 9 is clamped between the flange and the upper sleeve.

[0060] The lower bushing 5 - 2 is provided with a high voltage line inlet 12 and a ground line inlet 13 .

[0061] like Figure 4 As shown, the exhaust gas absorption detection device includes a cold trap 14 and a detection system. After the exhaust gas is absorbed by the cold trap, it enters the detection system. Specifically, the detection system includes a Fourier transform infrared spectrometer 15, an ozone monitoring device 16 and an MRU emission monitoring system 17.

[0062] like Figures 5 to 10 As shown, the diameter of the openings on the high-voltage electrode plate 10 is 1-1.5 mm; the number of openings on the high-voltage electrode plate 10 is 1-17.

[0063] The diameter of the openings on the ground electrode plate 11 is 0.5-1 mm, and the number of the openings on the ground electrode plate 11 is 1-17.

[0064] The openings on the high-voltage electrode plate 10 or the ground electrode plate 11 are asymmetrically arranged.

[0065] The thickness of the inner ring body 9 - 2 of the alumina ceramic ring 9 is 1 to 6 mm, that is, the discharge gap between the high-voltage electrode plate 10 and the ground electrode plate 11 is 1 to 6 mm.

[0066] Example 2

[0067] A jet plasma nitrogen fixation method based on nanosecond pulsed spark discharge, based on the nitrogen fixation device of Example 1, comprises:

[0068] S1: Water is continuously introduced into the reaction vessel through a circulation pump, and the water flows out through the liquid outlet; the water level is 3-5 mm below the ground electrode plate;

[0069] Number of ground electrode selection holes: 6 holes ( Figure 8 ), aperture 1mm; the number of holes for high voltage electrode selection is 16 holes ( Figure 10 The aperture is 1 mm. The inner ring of the alumina ceramic ring is 2 mm thick. The ground electrode and high-voltage electrode are embedded below and above the alumina ceramic ring, respectively.

[0070] S2: nitrogen or air at a flow rate of 5 L / min is introduced into the plasma generating chamber through the gas inlet;

[0071] S3: Turn on the nanosecond pulse power switch, and spark discharge is generated between the high-voltage electrode plate and the electrode plate; the reaction gas generates plasma in the spark discharge area; the plasma flows with the reaction gas, forms a jet through the opening of the ground electrode plate, enters the reaction liquid and reacts with the reaction liquid to form nitrate and nitrite, which dissolve in the reaction liquid; in addition, obvious ozone is generated, which promotes the further oxidation of nitrite to nitrate.

[0072] S4: After the reaction is completed, turn off the nano pulse power supply and circulation pump, and stop introducing the reaction gas.

[0073] Experimental results: The measured current and voltage waveforms are as follows: Figure 11 shown.

[0074] The product concentration (mg / L) was obtained under the conditions of 9kV nanosecond pulse power supply voltage, 2000Hz frequency, 500ns pulse width, 50ns rising and falling edges.

[0075]

[0076] Example 3

[0077] A plasma nitrogen fixation method based on nanosecond pulsed spark discharge, based on the nitrogen fixation device of Example 1, comprising:

[0078] S1: Water is continuously introduced into the reaction vessel through a circulation pump, and the water flows out through the liquid outlet; the water level is 1-2 mm above the ground electrode plate;

[0079] Ground electrode selection 5 holes ( Figure 7 ), aperture 1mm; the number of holes for high voltage electrode selection is 16 holes ( Figure 10 The aperture is 1 mm. The inner ring of the alumina ceramic ring is 2 mm thick. The ground electrode and high-voltage electrode are embedded below and above the alumina ceramic ring, respectively.

[0080] S2: nitrogen or air at a flow rate of 5 L / min is introduced into the plasma generating chamber through the gas inlet;

[0081] S3: Turn on the nanosecond pulse power switch, and spark discharge is generated between the high-voltage electrode plate and the electrode plate; the reaction gas generates plasma in the spark discharge area; the plasma flows with the reaction gas, forms bubbles through the openings of the ground electrode plate, enters the reaction liquid and reacts with the reaction liquid to form nitrate and nitrite, which dissolve in the reaction liquid; in addition, obvious ozone is generated, which promotes the further oxidation of nitrite to nitrate.

[0082] S4: After the reaction is completed, turn off the nano pulse power supply and circulation pump, and stop introducing the reaction gas.

[0083] Experimental results: The measured current and voltage waveforms are as follows: Figure 12 shown

[0084] The product concentration (mg / L) was obtained under the conditions of 9kV nanosecond pulse power supply voltage, 2000Hz frequency, 500ns pulse width, 50ns rising and falling edges.

[0085] <![CDATA[NO3 - ]]> <![CDATA[NO2 - ]]> <![CDATA[H202]]> 722 3 50

[0086] Example 4

[0087] A plasma nitrogen fixation method based on nanosecond pulsed spark discharge, comprising:

[0088] S1: The high-voltage electrode and the ground electrode in Example 1 are interchanged, with other conditions remaining unchanged. Water is continuously introduced into the reaction vessel via a circulation pump, and the water flows out through the liquid outlet; the water level is 3-5 mm below the high-voltage electrode.

[0089] High voltage electrode selection 6 holes ( Figure 8 ), aperture 1mm; the number of holes selected for the ground electrode is 16 holes ( Figure 10 The aperture is 1 mm. The inner ring of the alumina ceramic ring is 2 mm thick. The ground electrode and high-voltage electrode are embedded above and below the alumina ceramic ring, respectively.

[0090] S2: nitrogen or air at a flow rate of 5 L / min is introduced into the plasma generating chamber through the gas inlet;

[0091] S3: Turn on the nanosecond pulse power switch, and spark discharge is generated between the high-voltage electrode plates. The reaction gas generates plasma in the spark discharge area. The plasma flows with the reaction gas, forms a jet through the openings of the high-voltage electrode plates, enters the reaction liquid, and reacts with the reaction liquid to form nitrate and nitrite, which dissolve in the reaction liquid. In addition, obvious ozone is generated, which promotes the further oxidation of nitrite to nitrate.

[0092] S4: After the reaction is completed, turn off the nano pulse power supply and circulation pump, and stop introducing the reaction gas.

[0093] Experimental results: The measured current and voltage waveforms are as follows: Figure 13 shown

[0094] The product concentration (mg / L) was obtained under the conditions of 9kV nanosecond pulse power supply voltage, 2000Hz frequency, 500ns pulse width, 50ns rising and falling edges.

[0095]

[0096] Example 5

[0097] A plasma nitrogen fixation method based on nanosecond pulsed spark discharge, comprising:

[0098] S1: The high-voltage electrode and the ground electrode of Example 1 are interchanged. Under the condition that other conditions remain unchanged, water is continuously introduced into the reaction vessel through a circulation pump, and the water flows out through the liquid outlet; the water level is 1-2 mm above the high-voltage electrode plate.

[0099] High voltage electrode selection 5 holes ( Figure 7 ), aperture 1mm; the number of holes selected for the ground electrode is 16 holes ( Figure 10 The aperture is 1 mm. The inner ring of the alumina ceramic ring is 2 mm thick. The ground electrode and high-voltage electrode are embedded above and below the alumina ceramic ring, respectively.

[0100] S2: nitrogen or air at a flow rate of 5 L / min is introduced into the plasma generating chamber through the gas inlet;

[0101] S3: Turn on the nanosecond pulse power switch, and spark discharge is generated between the high-voltage electrode plate and the electrode plate; the reaction gas generates plasma in the spark discharge area; the plasma flows with the reaction gas, forms a jet through the opening of the ground electrode plate, enters the reaction liquid, and reacts with the reaction liquid to form nitrate and nitrite, which dissolve in the reaction liquid;

[0102] S4: After the reaction is completed, turn off the nano pulse power supply and circulation pump, and stop introducing the reaction gas.

[0103] Experimental results: The measured current and voltage waveforms are as follows: Figure 14 shown

[0104] The product concentration (mg / L) was obtained under the conditions of 9kV nanosecond pulse power supply voltage, 2000Hz frequency, 500ns pulse width, 50ns rising and falling edges.

[0105]

[0106] While the embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations of these embodiments are possible. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as set forth in the claims. Furthermore, the invention described herein is susceptible to other embodiments and may be practiced or implemented in a variety of ways.

Claims

1. A method for nitrogen fixation using a jet plasma based on nanosecond pulsed spark discharge, comprising a device for nitrogen fixation using a jet plasma based on nanosecond pulsed spark discharge, the device comprising a reaction vessel and a plasma generating device; The reaction vessel is provided with a liquid inlet and a liquid outlet; the liquid inlet is connected to a circulation pump; the reaction liquid is introduced into the reaction vessel through the circulation pump; the liquid outlet is connected to a collection container; The plasma generating device includes a tubular plasma generating chamber; the plasma generating chamber is fixed on the top of the reaction vessel; a gas inlet is provided on the top of the plasma generating chamber; the gas inlet is used to introduce reaction gas into the plasma generating chamber; the reaction vessel is also provided with an exhaust gas outlet, and the exhaust gas outlet is connected to the exhaust gas absorption detection device; a flow equalizing plate is provided in the plasma generating chamber; an alumina ceramic ring is detachably installed in the plasma generating chamber below the flow equalizing plate; the alumina ceramic ring consists of an outer ring body and an inner ring body; electrode plates are provided on the top and bottom of the inner ring body; one of them is a high-voltage electrode plate and the other is a ground electrode plate; openings for the reaction gas to pass through are provided on the high-voltage electrode plate and the ground electrode plate; the high-voltage electrode plate is connected to a nanosecond pulse power supply; and the ground electrode plate is grounded; The plasma generating chamber is composed of an upper sleeve and a lower sleeve; the lower sleeve is sleeved on the bottom of the upper sleeve, and a ring-shaped flange is provided on the inner side of the bottom of the lower sleeve; an alumina ceramic ring is clamped between the flange and the upper sleeve; The tail gas absorption detection device includes a cold trap and a detection system, and the tail gas enters the detection system after being absorbed by the cold trap; Also includes at least one of the following technical features: 1): The aperture of the opening on the high-voltage electrode plate is 1~1.5mm; the number of openings on the high-voltage electrode plate is 1~17; 2): The diameter of the openings on the ground electrode plate is 0.6~1mm, and the number of openings on the ground electrode plate is 1~17; 3): The openings on the high-voltage electrode plate or the ground electrode plate are asymmetrically arranged; 4): The inner ring body thickness of the alumina ceramic ring is 1~6mm; It is characterized by: The method comprises: S1: The reaction liquid is continuously introduced into the reaction vessel through a circulation pump, and the reaction liquid flows out through the liquid outlet; the liquid level of the reaction liquid is maintained in one of the following two states: 1) The liquid level is 3~5mm below the bottom of the lowest electrode plate; 2) The liquid level does not exceed the bottom electrode plate; S2: introducing reaction gas into the plasma generating chamber through the gas inlet; S3: Turning on the nanosecond pulse power switch generates a spark discharge between the high-voltage electrode plate and the ground electrode plate. The reaction gas generates plasma in the spark discharge area. The plasma flows with the reaction gas, forms a jet or bubble through the opening on the bottom electrode plate, enters the reaction liquid, and reacts with the reaction liquid to form nitrate and nitrite, which dissolve in the reaction liquid. S4: After the reaction is completed, turn off the nano pulse power supply and circulation pump, and stop introducing the reaction gas.

2. The jet plasma nitrogen fixation method based on nanosecond pulsed spark discharge according to claim 1, characterized in that: The reaction gas is a mixture of nitrogen and oxygen, air or pure nitrogen.

3. The jet plasma nitrogen fixation method based on nanosecond pulsed spark discharge according to claim 2, characterized in that: The flow rate of the reaction gas is 3-8 L / min.

4. The jet plasma nitrogen fixation method based on nanosecond pulsed spark discharge according to claim 3, characterized in that: The reaction liquid is water.

5. The jet plasma nitrogen fixation method based on nanosecond pulsed spark discharge according to claim 4, characterized in that: The nanosecond pulse power supply voltage is 9 kV, the frequency is 2000 Hz, the pulse width is 500 ns, and the rising edge and the falling edge are both 50 ns.

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