Device and method for synthesizing ammonium nitrate through underwater bubble plasma electro-catalysis

Abstract

In the device, a plurality of low-temperature plasma reactors are fixed in an absorption liquid storage tank in an array manner, a quartz tube is immersed in liquid in the absorption liquid storage tank, and a plurality of through micropores are uniformly distributed in the bottom of the quartz tube; the lower end of the connecting fastener is fixed with the orifice of the quartz tube, and the side edge of the connecting fastener is provided with an air tube; the metal electrode is fixed through the upper end of the connecting firmware and extends into the quartz tube to serve as a high-voltage electrode; the discharge power supply is connected with the metal electrode and the ground electrode, so that the low-temperature plasma reactor generates bubble plasma in liquid; the electrolytic cell is communicated with an absorption liquid storage tank through a switch pipeline, the working electrode is provided with foamy copper as an electro-catalysis material, and the working electrode, the platinum wire counter electrode and the silver / silver chloride reference electrode form a three-electrode electrochemical structure to electrocatalytically synthesize ammonium nitrate in the electrolytic cell.

Description

Technical Field

[0001] The invention relates to the technical field of atmospheric pressure plasma nitrogen fixation, in particular to a device and a method for electrocatalytic synthesis of ammonium nitrate by underwater bubble plasma. Background Art

[0002] Nitrogen fertilizer is the most widely used fertilizer in the world, playing a vital role in increasing food production and maintaining the livelihoods of about 40% of the world's population. Traditional agriculture generally uses solid nitrogen fertilizers, which are mainly produced by chemical plants and then transported to agricultural production sites. Both its production and transportation processes rely heavily on fossil fuels, causing large amounts of greenhouse gas emissions. In addition, when solid nitrogen fertilizers are applied, they inevitably seep into groundwater, resulting in a utilization rate of less than 50%. Recently, liquid fertilizers combined with precision irrigation systems have been shown to improve fertilizer utilization efficiency. Therefore, it is of great significance to develop a sustainable method for the production of liquid nitrogen fertilizers that can utilize renewable energy in a decentralized and on-demand manner.

[0003] In the existing technology, the large-scale industrial production of NH4NO3 mainly relies on the Haber-Bosch (HB) process and the Ostwald process. The energy consumed by HB ammonia synthesis accounts for 1%-2% of the world's total energy consumption, and the emission of carbon dioxide exceeds 300 million tons. On the other hand, the Ostwald process requires a strict high temperature and high pressure environment and is the largest industrial emission source of greenhouse gas N2O. People have been seeking sustainable nitrogen fixation strategies under environmental conditions to replace or supplement the traditional HB process.

[0004] The information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0005] In view of the shortcomings or defects of the prior art, a device and method for underwater bubble plasma electrocatalytic synthesis of ammonium nitrate are provided, which can stably produce ammonium nitrate fertilizer at an energy consumption of 25.3 MJ / mol, and 44.22% of the production cost is attributed to electricity consumption, highlighting the optimization potential of renewable energy integration and promoting the development of sustainable agriculture.

[0006] The purpose of the present invention is achieved through the following technical solutions.

[0007] An underwater bubble plasma electrocatalytic synthesis of ammonium nitrate device comprises:

[0008] An absorption liquid storage tank is a hollow structure for storing liquid, and a ground electrode is provided at the outer bottom of the absorption liquid storage tank;

[0009] A plurality of low-temperature plasma reactors are fixed in an array in the absorption liquid storage tank, and the low-temperature plasma reactors include:

[0010] A quartz tube, which is immersed in the liquid in the absorption liquid storage tank, and the bottom of the quartz tube is evenly distributed with a plurality of penetrating micropores;

[0011] A connecting piece, the lower end of which is fixed with the pipe opening of the quartz tube, and the side of the connecting piece is provided with an air pipe;

[0012] A metal electrode, which is fixed via the upper end of the connecting piece and extends into the quartz tube as a high-voltage electrode;

[0013] A discharge power supply connected to the metal electrode and the ground electrode so that the low-temperature plasma reactor generates bubble plasma in the liquid;

[0014] An electrolytic cell is connected to the absorption liquid storage tank via a switch pipe, and the electrolytic cell comprises:

[0015] a tank body, which receives liquid from the absorption liquid storage tank,

[0016] The working electrode is provided with copper foam as the electrocatalytic material.

[0017] A platinum wire counter electrode is inserted into the tank.

[0018] a silver / silver chloride reference electrode, which is inserted into the tank,

[0019] A proton exchange membrane is arranged in an electrolytic cell to isolate cathode and anode products. A working electrode, a platinum wire counter electrode and a silver / silver chloride reference electrode constitute a three-electrode electrochemical structure to electrocatalytically synthesize ammonium nitrate in the electrolytic cell.

[0020] In the device for electrocatalytic synthesis of ammonium nitrate by underwater bubble plasma, a copper foil connecting wire is attached to the outer bottom of the absorption liquid storage tank as a ground electrode.

[0021] In the device for electrocatalytic synthesis of ammonium nitrate using underwater bubble plasma, the micropores are evenly distributed around the tube wall, have a pore diameter of 100 μm, and vertically penetrate the tube wall.

[0022] In the device for underwater bubble plasma electrocatalytic synthesis of ammonium nitrate, the connecting fixture is a T-shaped variable diameter three-way joint, and the three side interfaces are respectively adapted to the diameters of the quartz tube, the metal electrode and the air pipe, and the connecting fixture is made of insulating material.

[0023] In the device for electrocatalytic synthesis of ammonium nitrate by underwater bubble plasma, threaded structures are formed on the three side interfaces on the connecting fixture, at least one ferrule structure is placed inside the threaded structure and sleeved on the outside of the quartz tube, and the quartz tube is fixed by the threaded structure to ensure air tightness.

[0024] In the device for electrocatalytic synthesis of ammonium nitrate using underwater bubble plasma, the connecting piece is made of polytetrafluoroethylene, and the threaded structure includes a nut.

[0025] In the device for electrocatalytic synthesis of ammonium nitrate using underwater bubble plasma, the metal electrode is a finely ground solid round rod with uniform thickness.

[0026] In the device for electrocatalytic synthesis of ammonium nitrate by underwater bubble plasma, the tip of the metal electrode is polished smooth to ensure stable discharge to generate plasma.

[0027] In the device for electrocatalytic synthesis of ammonium nitrate using underwater bubble plasma, the discharge power supply is a pulse power supply, the discharge voltage is at least 7 kV, and the discharge frequency is at least 3 kHz.

[0028] The synthesis method of the device for electrocatalytic synthesis of ammonium nitrate by underwater bubble plasma comprises the following steps:

[0029] Pre-activating air through a low-temperature plasma reactor to form a mixed gas including nitrogen oxides;

[0030] The mixed gas is spark-discharged at the bubble interface, and the generated nitrogen oxides are bubbled into the liquid in the form of bubbles to form nitrate and nitrite solutions;

[0031] The nitrate and nitrite solutions in the absorption liquid storage tank are introduced into the electrolytic cell as electrolyte for partial reduction, and the ammonium nitrate solution is obtained by electrolysis for a predetermined time.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The invention is low-carbon and environmentally friendly. The device can solve the problem of excessive carbon emissions in the current ammonium nitrate fertilizer production field, overcome the dependence of the ammonium nitrate fertilizer production process on fossil fuels, directly synthesize ammonium nitrate from air and water at normal temperature and pressure, and is compatible with renewable electricity, so as to achieve zero carbon emissions in the production process. Plasma discharge generates high-energy electrons through a strong electric field under mild conditions, activates nitrogen molecules and oxygen molecules, and promotes the formation of nitrogen oxides. On the other hand, electrocatalysis can selectively convert reactants (N2 or nitrogen oxide aqueous solution) into ammonia. The two basic processes of plasma-assisted activation of air to produce nitrogen oxides in solution and electrochemical conversion of the produced nitrogen oxides into ammonia are coupled. Plasma bubbles are efficient gas-liquid discharge structures that activate N2 and O2 molecules. Introducing high-density discharge in underwater bubbles can increase the gas-liquid discharge area and strengthen the mass transfer of plasma active species, thereby promoting the generation of nitrogen oxides in water bodies. The direct conversion of air and water into NH4NO3 as liquid nitrogen fertilizer has lower energy consumption and higher product yield.

[0034] Convenient and safe. The existing ammonium nitrate fertilizer production method not only produces a large carbon footprint due to the production of solid NH4NO3, but also increases the risk of explosion during long-distance transportation. This device is suitable for small-scale, distributed on-site production, and can be started and stopped immediately, without the need to introduce H2, eliminating the risk of explosion, and is convenient and safe.

[0035] Low energy consumption. The energy consumption of the present invention is at least 2.5 times lower than that of HB method for nitrogen fixation. In addition, the present device introduces bubbles to promote gas-liquid mass transfer, reduce the breakdown voltage, and achieves nitrogen fixation energy consumption of 25.3 MJ / mol. It is in a leading position in the field of plasma nitrogen fixation and has the advantages of low energy consumption and high yield. The present device is driven by a nanosecond pulse power supply, which can promote ionization during the discharge start-up process and promote highly unbalanced electron energy distribution, thereby significantly improving energy efficiency.

[0036] The above description is only an overview of the technical solution of the present invention. In order to make the technical means of the present invention clearer and to achieve the extent that those skilled in the art can implement it according to the contents of the specification, and in order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are exemplified below. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of illustrating the preferred embodiments and are not considered to be limitations of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work. Moreover, the same reference numerals are used to represent the same components throughout the drawings.

[0038] In the attached picture:

[0039] Figure 1 It is a structural schematic diagram of the device of the present invention;

[0040] Figure 2 The overall process diagram of producing ammonium nitrate fertilizer using the device of the present invention is as follows;

[0041] Figure 3 A statistical diagram showing the variation of the output of nitrogen-containing compounds generated by the plasma part of the device of the present invention with the frequency of the pulse power supply;

[0042] Figure 4 A statistical graph showing the change in the output of ammonium nitrate produced by the electrocatalytic part of the device of the present invention over time;

[0043] Figure 5 The present invention is a hydroponic experiment of Chinese cabbage using the ammonium nitrate fertilizer produced by the device of the present invention.

[0044] The present invention is further explained below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0045] The specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0046] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the attached claims.

[0047] To facilitate understanding of the embodiments of the present invention, several specific embodiments will be further explained below with reference to the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.

[0048] For a better understanding, Figures 1 to 5 As shown, an underwater bubble plasma electrocatalytic synthesis of ammonium nitrate device comprises:

[0049] The absorption liquid storage tank 2 is a hollow structure for storing liquid, and a ground electrode is provided at the outer bottom of the absorption liquid storage tank 2;

[0050] A plurality of low-temperature plasma reactors 1 are fixed in an array in the absorption liquid storage tank 2. The low-temperature plasma reactor 1 comprises:

[0051] A quartz tube 4, which is immersed in the liquid in the absorption liquid storage tank 2, and a plurality of penetrating micropores are evenly distributed on the bottom of the quartz tube 4;

[0052] A connecting piece 5, the lower end of which is fixed with the pipe opening of the quartz tube 4, and a gas pipe is provided on the side of the connecting piece 5;

[0053] A metal electrode 6, which is fixed via the upper end of the connecting piece 5 and extends into the quartz tube 4 as a high-voltage electrode;

[0054] A discharge power supply, which is connected to the metal electrode 6 and the ground electrode, so that the low-temperature plasma reactor 1 generates bubble plasma in the liquid;

[0055] The electrolytic cell 3 is connected to the absorption liquid storage tank 2 via a switch pipe 7. The electrolytic cell 3 includes:

[0056] A tank body, which contains liquid from the absorption liquid storage tank 2,

[0057] The working electrode is provided with copper foam as the electrocatalytic material.

[0058] A platinum wire counter electrode is inserted into the tank.

[0059] a silver / silver chloride reference electrode, which is inserted into the tank,

[0060] The proton exchange membrane is arranged in the electrolytic cell 3 to isolate the cathode and anode products. The working electrode, the platinum wire counter electrode and the silver / silver chloride reference electrode constitute a three-electrode electrochemical structure to electrocatalytically synthesize ammonium nitrate in the electrolytic cell 3. The left half of the electrolytic cell is the cathode, which is inserted with the reference electrode and the working electrode; ammonium nitrate is produced at the cathode; the bubble plasma in the absorption liquid storage tank plays a role in improving gas-liquid mass transfer, reducing breakdown voltage and reducing energy consumption.

[0061] In a preferred embodiment of the device for electrocatalytic synthesis of ammonium nitrate by underwater bubble plasma, a copper foil connecting wire is attached to the outer bottom of the absorption liquid storage tank 2 as a ground electrode.

[0062] In a preferred embodiment of the device for underwater bubble plasma electrocatalytic synthesis of ammonium nitrate, the micropores are evenly distributed around the tube wall, have a pore diameter of 100 μm and vertically penetrate the tube wall.

[0063] In a preferred embodiment of the device for underwater bubble plasma electrocatalytic synthesis of ammonium nitrate, the connecting fixture 5 is a T-shaped variable diameter three-way joint, and the three side interfaces are respectively adapted to the diameters of the quartz tube 4, the metal electrode 6 and the air pipe, and the connecting fixture 5 is made of insulating material.

[0064] In a preferred embodiment of the device for underwater bubble plasma electrocatalytic synthesis of ammonium nitrate, a threaded structure is formed on the three-side interfaces on the connecting fixture 5, and at least one ferrule structure is placed inside the threaded structure and sleeved on the outside of the quartz tube 4, and the quartz tube 4 is fixed by the threaded structure to ensure air tightness.

[0065] In a preferred embodiment of the device for electrocatalytic synthesis of ammonium nitrate by underwater bubble plasma, the connecting piece 5 is made of polytetrafluoroethylene, and the threaded structure includes a nut.

[0066] In a preferred embodiment of the device for electrocatalytic synthesis of ammonium nitrate by underwater bubble plasma, the metal electrode 6 is a finely ground solid round rod with uniform thickness.

[0067] In a preferred embodiment of the device for electrocatalytic synthesis of ammonium nitrate by underwater bubble plasma, the tip of the metal electrode 6 is polished smooth to ensure stable discharge to generate plasma.

[0068] In a preferred embodiment of the device for electrocatalytic synthesis of ammonium nitrate using underwater bubble plasma, the discharge power supply is a pulse power supply, the discharge voltage is at least 7 kV, and the discharge frequency is at least 3 kHz.

[0069] The synthesis method of the device for electrocatalytic synthesis of ammonium nitrate by underwater bubble plasma comprises the following steps:

[0070] Pre-activating air through a low-temperature plasma reactor 1 to form a mixed gas including nitrogen oxides;

[0071] The mixed gas is spark-discharged at the bubble interface, and the generated nitrogen oxides are bubbled into the liquid in the form of bubbles to form nitrate and nitrite solutions;

[0072] The nitrate and nitrite solutions in the absorption liquid storage tank 2 are introduced into the electrolytic cell 3 as electrolyte for partial reduction, and the ammonium nitrate solution is obtained by electrolysis for a predetermined time.

[0073] In one embodiment, the nitrogen oxides include NO and NO2.

[0074] In one embodiment, the metal electrode 6 is connected to the positive pole of the power supply, and good contact is ensured by means of wire winding, metal clips, etc. The electrode is placed in the quartz tube 4, and the distance between the bottom of the electrode and the bottom of the quartz tube 4 is slightly greater than the distance between the micropore and the bottom of the quartz tube 4. The absorption liquid storage tank 2 should be of a fixed shape. Preferably, a double-layer jacket container can be selected to pass cooling water to ensure constant temperature during the discharge process. The absorption liquid storage tank 2 is airtight to ensure maximum product selectivity and yield. The electrocatalytic partial reaction device consists of an electrochemical workstation and an H-type electrolyzer. The electrochemical workstation is a CHI potentiostat (CHI760E), and the electrocatalytic process is carried out in an H-type electrolyzer. The cathode and the anode are separated by a proton exchange membrane. A three-electrode electrochemical configuration is adopted, including a working electrode (WE), a platinum wire counter electrode (CE) and a silver / silver chloride reference electrode. WE is equipped with foamed copper as an electrocatalytic material.

[0075] In one embodiment, the low-temperature plasma reactor 1 activates air to form a mixed gas composed of nitrogen oxides such as NO and NO2; then the mixed gas is bubbled into water in the form of bubbles to form nitrate and nitrite solutions; the nitrite solution in the absorption liquid storage tank 2 is passed into the electrolytic cell 3 as an electrolyte for electrolysis for a certain period of time to obtain an ammonium nitrate solution. The final product can be directly used as a liquid nitrogen fertilizer for irrigating farmland. To solve the problem of excessive carbon emissions in the current ammonium nitrate fertilizer production field, overcome the dependence of the ammonium nitrate fertilizer production process on fossil fuels, and directly synthesize ammonium nitrate from air and water, renewable electricity can be compatible with this process in the future, and zero carbon emissions can be achieved in the production process.

[0076] In one embodiment, the gas introduced through the gas pipe can be external gas or a gas cylinder, and a gas mass flow controller is required to control the flow rate to be small and stable. In a preferred embodiment of the present invention, the gas flow rate is controlled at 1 L / min.

[0077] The metal electrode 6 in the device can be made of common metals, including but not limited to 304 stainless steel, tungsten steel, etc. It should be noted that the metal electrode 6 should have a smooth surface to ensure uniform and stable tip discharge and extend its service life.

[0078] The power supply that provides voltage for discharge is a nanosecond pulse power supply, and its voltage should be above 7kV and its frequency should be above 3kHz.

[0079] In addition, the absorption liquid storage tank 2 herein includes any form of barrels, bottles, boxes, cans, barrels, tubes, cups, and other fixed-shape containers that can hold liquid.

[0080] The practical effects of a specific embodiment of the present invention are listed below:

[0081] According to the above specific implementation manner, the input gas is air, and the gas flow rate is 1L / min. Figure 3 The results of plasma oxidation products in the solution are shown in Figure 2. It can be seen that with the increase of power frequency, the output of liquid nitrogen oxides continues to increase, reaching the highest at 5kHz, reaching 200μmol. Figure 4 The results of the ammonium nitrate reduction products produced by the electrocatalytic part are shown in Figure 2. Based on the measurement results of the liquid phase concentration, it can be inferred that ammonium nitrate is formed in the solution between 25 and 30 minutes of electrolysis. In order to verify the effectiveness of plasma electrocatalytic ammonium nitrate fertilizer, we conducted a hydroponic experiment using Chinese cabbage. The results are shown in Figure 2. Figure 5As shown. We found that the growth rate of the fertilized group was significantly accelerated, and the difference in leaf size and stem length between the fertilized and unfertilized groups became more and more obvious over time. On the 21st day, the stem length and leaf length of the experimental group reached 3.5 cm and 3.28 cm, respectively, while the control group was 1.83 cm and 2.12 cm, respectively, with the stem length and leaf length increasing by about 91.26% and 54.72%, respectively. From the growth photos, it can be seen that the plants in the experimental group grew faster and had larger and more lush leaves. In addition, comparing the growth status of the two groups of plants at 17 and 21 days, the leaves of the control group appeared dull and yellow at the edges, while the leaves of the experimental group remained bright green. This may be because our liquid fertilizer provides the nitrogen required for leaf growth, while the control group has yellowing leaves due to a long-term lack of sufficient nitrogen. These results show that the liquid ammonium nitrate fertilizer produced in our study has a positive effect on the growth of agricultural plants.

[0082] The basic principles of the present application are described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, effects, etc. mentioned in the present application are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. are required by each embodiment of the present application. In addition, the specific details disclosed above are only for the purpose of illustration and ease of understanding, not for limitation, and the above details do not limit the present application to being implemented by adopting the above specific details.

[0083] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although multiple example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

Claims

1. A device for electrocatalytic synthesis of ammonium nitrate by underwater bubble plasma, characterized in that: These include, An absorption liquid storage tank is a hollow structure for storing liquid, and a ground electrode is provided at the outer bottom of the absorption liquid storage tank; A plurality of low-temperature plasma reactors are fixed in an array in the absorption liquid storage tank, and the low-temperature plasma reactors include: A quartz tube, which is immersed in the liquid in the absorption liquid storage tank, and the bottom of the quartz tube is evenly distributed with a plurality of penetrating micropores; A connecting piece, the lower end of which is fixed with the pipe opening of the quartz tube, and the side of the connecting piece is provided with an air pipe; A metal electrode, which is fixed via the upper end of the connecting piece and extends into the quartz tube as a high-voltage electrode; A discharge power supply connected to the metal electrode and the ground electrode so that the low-temperature plasma reactor generates bubble plasma in the liquid; An electrolytic cell is connected to the absorption liquid storage tank via a switch pipe, and the electrolytic cell comprises: a tank body, which receives liquid from the absorption liquid storage tank, The working electrode is provided with copper foam as the electrocatalytic material. A platinum wire counter electrode is inserted into the tank. a silver / silver chloride reference electrode, which is inserted into the tank, A proton exchange membrane is arranged in an electrolytic cell to isolate cathode and anode products. A working electrode, a platinum wire counter electrode and a silver / silver chloride reference electrode constitute a three-electrode electrochemical structure to electrocatalytically synthesize ammonium nitrate in the electrolytic cell.

2. The device for underwater bubble plasma electrocatalytic synthesis of ammonium nitrate according to claim 1, characterized in that: Preferably, a copper foil connecting wire is attached to the outer bottom of the absorption liquid storage tank as a ground electrode.

3. The device for underwater bubble plasma electrocatalytic synthesis of ammonium nitrate according to claim 1, characterized in that: The pore size of the micropores is 100 μm.

4. The device for electrocatalytic synthesis of ammonium nitrate by underwater bubble plasma according to claim 1, characterized in that: The connecting piece is made of insulating material.

5. The device for underwater bubble plasma electrocatalytic synthesis of ammonium nitrate according to claim 1, characterized in that: The connecting parts are made of polytetrafluoroethylene.

6. The device for underwater bubble plasma electrocatalytic synthesis of ammonium nitrate according to claim 1, characterized in that: The metal electrode is a finely ground solid round rod with uniform thickness.

7. The device for electrocatalytic synthesis of ammonium nitrate by underwater bubble plasma according to claim 1, characterized in that: The tip of the metal electrode is polished and smooth to ensure stable discharge and generate plasma.

8. The device for underwater bubble plasma electrocatalytic synthesis of ammonium nitrate according to claim 1, characterized in that: The discharge voltage is at least 7 kV.

9. A method for synthesizing the device for electrocatalytic synthesis of ammonium nitrate using underwater bubble plasma as described in any one of claims 1 to 8.

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