A device and method for synthesizing ammonia

Abstract

The present invention relates to the technical field of ammonia synthesis, and specifically to a device and method for synthesizing ammonia, wherein the device comprises: a microwave power supply, a microwave backflow prevention device, a three-pin dispenser, a microwave coaxial resonant cavity, and a dielectric barrier discharge reactor connected in sequence; the dielectric barrier discharge reactor is connected to a nanosecond pulse power supply, and is filled with a catalyst; a nitrogen source and a hydrogen source are connected to the gas inlet of the microwave coaxial resonant cavity. A mixed gas of nitrogen and hydrogen forms an atmospheric pressure nitrogen and hydrogen microwave discharge plasma at the opening of the microwave coaxial resonant cavity; the generated atmospheric pressure nitrogen and hydrogen microwave discharge plasma acts together with the plasma generated in the dielectric barrier discharge reactor, and under the synergistic effect of the catalyst in the dielectric barrier discharge reactor, ammonia synthesis is achieved, and the gas and catalyst surface temperatures can be separately controlled, and the conversion efficiency and yield of the generated ammonia are high.

Description

Technical Field

[0001] The present invention relates to the technical field of ammonia synthesis, and in particular to a device and method for synthesizing ammonia. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Ammonia is a very important chemical substance and an important raw material for industrial and agricultural production. Ammonia also has a high energy density and hydrogen content, and is a potential hydrogen storage carrier. The Haber-Bosch process currently used in large-scale industrial ammonia synthesis consumes a lot of energy and has a negative impact on the environment. With environmental problems becoming increasingly prominent and energy shortages, it is urgent to explore a green, energy-saving and sustainable ammonia synthesis technology.

[0004] Plasma contains a large number of high-energy electrons, active particles, excited particles and free radicals, which can excite, dissociate or ionize nitrogen and hydrogen molecules under low temperature and normal pressure conditions. Plasma synthesis of ammonia uses nitrogen and hydrogen as raw materials. In combination with conventional catalytic synthesis of ammonia, it can effectively improve the yield and energy efficiency of synthetic ammonia and is an effective method for synthesizing ammonia. However, most traditional catalytic synthesis of ammonia devices cannot separately control the gas and catalyst surface temperature, resulting in low conversion efficiency and low yield. Summary of the invention

[0005] In view of the technical problems existing in the above-mentioned prior art, the purpose of the present invention is to provide an apparatus and method for synthesizing ammonia, which realizes plasma catalytic synthesis of ammonia under atmospheric pressure and low temperature conditions through the synergistic effect of microwave discharge, dielectric barrier discharge reactor and catalyst.

[0006] Specifically, the technical solution of the present invention is as follows:

[0007] In a first aspect of the present invention, there is provided a device for synthesizing ammonia, comprising:

[0008] A microwave power supply, a microwave backflow prevention device, a three-pin dispenser, a microwave coaxial resonant cavity, and a dielectric barrier discharge reactor are connected in sequence;

[0009] The dielectric barrier discharge reactor is connected to a nanosecond pulse power supply, and a catalyst is filled inside the dielectric barrier discharge reactor;

[0010] A nitrogen source and a hydrogen source are connected to the gas inlet of the microwave coaxial resonant cavity.

[0011] In a second aspect of the present invention, a method for synthesizing ammonia is provided, comprising the steps of:

[0012] A mixed gas of nitrogen and hydrogen forms an atmospheric pressure nitrogen and hydrogen microwave discharge plasma at the opening of the microwave coaxial resonant cavity;

[0013] The atmospheric pressure nitrogen and hydrogen microwave discharge plasma generated works together with the plasma generated in the dielectric barrier discharge reactor, and under the synergistic effect of the catalyst in the dielectric barrier discharge reactor, ammonia synthesis is achieved.

[0014] The specific embodiments of the present invention have the following beneficial effects:

[0015] In an embodiment of the present invention, a nitrogen-hydrogen mixed gas passes through the interior of a microwave discharge resonant cavity and a dielectric barrier discharge reactor, and plasma catalytic synthesis of ammonia is achieved under atmospheric pressure and low temperature conditions through the synergistic effect of microwave discharge, dielectric barrier discharge reactor and catalyst. The gas and catalyst surface temperatures can be separately controlled, and the conversion rate and yield are high. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0017] Figure 1 A schematic diagram of the structure of a device for synthesizing ammonia in one or more embodiments of the present invention;

[0018] Among them, 1. microwave power supply, 2. circulator, 3. water load, 4. three-pin matcher, 5. microwave energy inlet, 6. gas inlet, 7. gas outlet, 8. microwave coaxial resonant cavity, 9. dielectric barrier discharge reactor, 10. high voltage electrode, 11. nanosecond pulse power supply, 12. infrared thermal imager, 13. gas chromatograph, 14. container with sulfuric acid solution, 15. Rogowski coil, 16. ground electrode, 17. tubular furnace, 18. oscilloscope, 19. computer, 20. nitrogen, 21. hydrogen, 22. pressure reducing valve, 23. flow meter, 24. thermocouple thermometer, 25. air heater, 26. flow equalizer, 27. catalyst. DETAILED DESCRIPTION

[0019] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in the present application have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0020] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0021] In one embodiment of the present invention, there is provided a device for synthesizing ammonia, comprising:

[0022] A microwave power supply, a microwave backflow prevention device, a three-pin dispenser, a microwave coaxial resonant cavity, and a dielectric barrier discharge reactor are connected in sequence;

[0023] The dielectric barrier discharge reactor is connected to a nanosecond pulse power supply, and a catalyst is filled inside the dielectric barrier discharge reactor;

[0024] A nitrogen source and a hydrogen source are connected to the gas inlet of the microwave coaxial resonant cavity.

[0025] Microwave power is used to drive microwave discharge; microwave discharge is a discharge plasma device that uses waveguides or transmission lines to transmit microwave energy under the excitation of microwave power to form a non-equilibrium discharge plasma in the microwave resonant cavity. Compared with other forms of gas discharge, microwave discharge has the advantages of uniformity and stability, high energy conversion efficiency, no electrode pollution, and high density of charged particles and active particles.

[0026] The microwave backflow prevention device is used to isolate the reflected waves to prevent them from damaging the microwave power supply;

[0027] The three-pin adapter performs impedance matching on the microwave transmission system;

[0028] A microwave coaxial resonant cavity is used to form an atmospheric pressure nitrogen and hydrogen microwave discharge plasma at the opening of the coaxial resonant cavity.

[0029] The dielectric barrier discharge reactor has low energy consumption, uniform and stable discharge, simple reactor structure, and can also form interactions and synergistic effects with catalysts, making it suitable for plasma catalysis under atmospheric pressure. The packed bed dielectric barrier discharge has high electric field strength and electron energy, which can cause more frequent electron impact ionization, excitation, decomposition and other plasma reactions, produce abundant charged particles, free radicals and excited state particles, and activate plasma catalysis with higher energy efficiency.

[0030] Dielectric barrier discharge plasma excited by nanosecond pulse power supply has the advantages of high field strength and low temperature, and is easy to achieve uniform discharge. The plasma can be effectively adjusted by changing the pulse parameters. By optimizing the catalyst and dielectric barrier discharge reactor combined with nanosecond pulse power supply excitation, the gas conversion rate and energy efficiency of dielectric barrier discharge plasma catalytic ammonia synthesis can be reasonably regulated.

[0031] In an embodiment of the present invention, a nitrogen-hydrogen mixed gas passes through a microwave discharge resonant cavity and a dielectric barrier discharge reactor, and plasma catalytic synthesis of ammonia is achieved under atmospheric pressure and low temperature conditions through the synergistic effect of microwave discharge, dielectric barrier discharge reactor and catalyst.

[0032] In some embodiments, the microwave backflow prevention device includes a circulator and a water load, and the inlet section and the outlet end of the circulator are respectively connected to the microwave power supply and the three-pin adapter.

[0033] Microwave backflow prevention devices are used to isolate reflected waves to prevent them from damaging microwave power supplies.

[0034] A circulator is a device that enables unidirectional circular transmission of electromagnetic waves. It is a three-port device, and the lower end is connected to a water load through a flange. The water load can adjust the water temperature through a cold water circulation pump.

[0035] Water load is a commonly used high-power microwave matching load. According to its working mode, it can be divided into two types: absorption water load and radiation water load. Both use flowing water as the microwave absorber. Water load can prevent backflow and reduce temperature at the same time.

[0036] In some embodiments, the length of the microwave coaxial resonant cavity is generally set to an odd number of quarter wavelengths, the air inlet end of the microwave coaxial resonant cavity is closed, and the air outlet end is open, that is, there is an opening, and the enhanced electric field can easily ionize the gas to form a plasma jet at the opening of the air outlet end.

[0037] In some embodiments, the dielectric barrier discharge reactor is a plate-plate electrode structure, and high-voltage electrodes are arranged on the upper and lower inner sides of the dielectric barrier discharge reactor, which are an upper high-voltage electrode and a lower high-voltage electrode respectively; the upper high-voltage electrode is connected to a nanosecond pulse power supply, and the lower high-voltage electrode is connected to a ground electrode;

[0038] In some embodiments, the nitrogen source is a nitrogen cylinder, and the hydrogen source is a hydrogen cylinder; a pressure reducing valve 22 is provided on the outlet pipes of the nitrogen cylinder and the hydrogen cylinder, and a flow meter 23 is provided downstream of the pressure reducing valve;

[0039] The nitrogen cylinder contains high-purity nitrogen gas, and the hydrogen cylinder contains high-purity hydrogen gas. The nitrogen and hydrogen gases are regulated in pressure and flow by pressure reducing valves and flow meters respectively, and are premixed to form a nitrogen-hydrogen mixed gas, which enters the interior of the microwave coaxial resonant cavity.

[0040] In some embodiments, an air heater 25 and a flow equalizer 26 are further provided between the nitrogen source and the hydrogen source and the gas inlet of the microwave coaxial resonant cavity, the nitrogen source and the hydrogen source are connected to the air heater 25, and the air heater 25 is connected to the flow equalizer 26 and the gas inlet of the microwave coaxial resonant cavity 8 in turn;

[0041] The air heater can change the temperature of the gas. According to the needs of plasma catalytic synthesis of ammonia, the nitrogen and hydrogen can be heated to a suitable temperature to improve the efficiency of plasma catalytic synthesis of ammonia. The purpose of the flow equalizer is to mix the nitrogen and hydrogen evenly.

[0042] In some embodiments, the air heater 25 is provided with a thermocouple thermometer 24;

[0043] Thermocouple thermometer is a temperature measuring instrument based on thermoelectric effect. It uses thermocouple thermometer to detect gas temperature and transmits the detected information to the computer to observe the appropriate gas temperature and adjust the gas temperature through the air heater.

[0044] In some embodiments, the synthetic ammonia device further comprises an infrared thermal imager 12, a gas chromatograph 13 and a container 14 filled with sulfuric acid; the infrared thermal imager 12 is connected to the gas outlet of the dielectric barrier discharge reactor 9, and the infrared thermal imager 12 is sequentially connected to the gas chromatograph 13 and the container 14 filled with sulfuric acid;

[0045] The infrared thermal imager is used to collect temperature information on the catalyst surface in real time; the product after nitrogen-hydrogen plasma catalytic synthesis of ammonia enters the gas chromatograph, which detects the properties of the product and transmits the test results and data to the computer; the container filled with sulfuric acid solution is used to absorb the generated ammonia.

[0046] In some embodiments, the device for synthesizing ammonia further comprises a Rogowski coil 15, an oscilloscope 18 and a computer 19, wherein the Rogowski coil 15 is located between the dielectric barrier discharge reactor 9 and the ground electrode 16, the Rogowski coil 16 is connected to the oscilloscope 18, one end of the oscilloscope 18 is connected to the gas chromatograph 13, and the other end is connected to the computer 17;

[0047] The Rogowski coil is used to detect the current signal, and the oscilloscope is used to display the current waveform.

[0048] Rogowski coil, also known as differential current sensor, is a toroidal coil uniformly wound on non-ferromagnetic material. The output signal is the differential of current with respect to time; through a circuit that integrates the output voltage signal, the input current can be truly restored. An oscilloscope is an instrument used to measure the shape of alternating current or pulse current waves.

[0049] After the computer analyzes and processes the results and data obtained from the gas chromatograph, the gas conversion rate is calculated.

[0050] In some embodiments, the dielectric barrier discharge reactor 9 is located in a tube furnace 17;

[0051] The main function of the tubular furnace is to heat the catalyst. The dielectric barrier discharge reactor containing the catalyst is placed in the tubular furnace. By setting the heating of the tubular furnace, the temperature of the catalyst surface can be controlled.

[0052] In one embodiment of the present invention, a method for synthesizing ammonia is provided, comprising the following steps:

[0053] A mixed gas of nitrogen and hydrogen forms an atmospheric pressure nitrogen and hydrogen microwave discharge plasma at the opening of the microwave coaxial resonant cavity;

[0054] The atmospheric pressure nitrogen and hydrogen microwave discharge plasma generated works together with the plasma generated in the dielectric barrier discharge reactor, and under the synergistic effect of the catalyst in the dielectric barrier discharge reactor, ammonia synthesis is achieved.

[0055] In some embodiments, the microwave power source is a 2.45 GHz microwave power source;

[0056] In some embodiments, the catalyst is magnesium chloride, preferably, the catalyst is a spherical magnesium chloride catalyst;

[0057] Magnesium chloride is introduced into plasma as a catalyst that can reduce the activation energy of nitrogen and hydrogen and an absorbent for in-situ absorption of ammonia. When magnesium chloride is used as an absorbent, a critical absorption intermediate compound Mg can be formed under plasma conditions. 3 N 2 and Mg(NH 3 ) 6 Cl 2 , absorb ammonia in situ; after the ammonia synthesis is completed, take out the catalyst in the reactor, put the catalyst into water, and it will produce ammonia after dissolution. After the catalyst is taken out of the water and dried, it is put into the reactor again. The catalyst can be recycled to improve the efficiency of plasma catalytic synthesis of ammonia.

[0058] In some embodiments, the dielectric barrier discharge reactor is excited by a nanosecond pulse power supply, the frequency of which is 0-15KHz, the output amplitude is 0-15KV, the pulse rise time and the pulse fall time are 50-500ns, and the gas is ionized inside the dielectric barrier discharge reactor to generate a discharge plasma.

[0059] In some embodiments, the surface temperature of the catalyst is 700K;

[0060] In some embodiments, the gas temperature is about 250°C;

[0061] In some embodiments, the flow rate of the gas is 90 mL / min.

[0062] In order to avoid heat transfer, the gas flow rate is increased and the gas is allowed to pass through the discharge plasma reactor quickly, so that the gas and catalyst surface temperatures can be controlled separately.

[0063] Example 1

[0064] like Figure 1 As shown, a device for synthesizing ammonia comprises:

[0065] A microwave power supply 1, a microwave backflow prevention device, a three-pin adapter 4, a microwave coaxial resonant cavity 8, and a dielectric barrier discharge reactor 9 are connected in sequence;

[0066] The dielectric barrier discharge reactor 9 is connected to the nanosecond pulse power supply 11, and the dielectric barrier discharge reactor 9 is filled with a catalyst 27; the dielectric barrier discharge reactor 9 is located in the tube furnace 17;

[0067] The dielectric barrier discharge reactor 9 is provided with high-voltage electrodes 10 on the upper and lower inner sides. The high-voltage electrodes include an upper high-voltage electrode and a lower high-voltage electrode, and are filled with a catalyst 27. The upper high-voltage electrode is connected to a nanosecond pulse power supply 11, and the lower high-voltage electrode is connected to a ground electrode 16.

[0068] The nitrogen source is a nitrogen cylinder, and the hydrogen source is a hydrogen cylinder; a pressure reducing valve 22 is respectively provided on the outlet pipes of the nitrogen cylinder and the hydrogen cylinder, and a flow meter 23 is respectively provided downstream of the pressure reducing valve;

[0069] An air heater 25 and a flow equalizer 26 are also provided between the nitrogen gas cylinder and the hydrogen gas cylinder and the gas inlet of the microwave coaxial resonant cavity 8. The nitrogen gas cylinder and the hydrogen gas cylinder are respectively connected to the air heater 25 through pipelines, and the air heater 25 is connected to the flow equalizer 26 and the gas inlet of the microwave coaxial resonant cavity 8 in turn; a thermocouple thermometer 24 is provided in the air heater 25;

[0070] The synthetic ammonia device further comprises an infrared thermal imager 12, a gas chromatograph 13 and a container 14 filled with sulfuric acid; the infrared thermal imager 12 is connected to the gas outlet of the dielectric barrier discharge reactor 9, and the infrared thermal imager 12 is connected to the gas chromatograph 13 and the container 14 filled with sulfuric acid in sequence;

[0071] The device for synthesizing ammonia also includes a Rogowski coil, an oscilloscope and a computer. The Rogowski coil is located between the dielectric barrier discharge reactor and the grounding electrode. The Rogowski coil is connected to the oscilloscope. One end of the oscilloscope is connected to the gas chromatograph, and the other end is connected to the computer.

[0072] Example 2

[0073] A method for synthesizing ammonia comprises the following steps:

[0074] A mixed gas of nitrogen and hydrogen in a volume ratio of 2:1 is heated to 250°C and flows evenly into a microwave coaxial resonant cavity, forming an atmospheric pressure nitrogen and hydrogen microwave discharge plasma at the opening of the microwave coaxial resonant cavity. The ejected microwave discharge plasma enters a dielectric barrier discharge reactor, and the microwave discharge plasma and the plasma generated in the dielectric barrier discharge reactor work together, and under the action of the catalyst in the dielectric barrier discharge reactor, ammonia synthesis is achieved;

[0075] The dielectric barrier discharge reactor is excited by a nanosecond pulse power supply with a frequency of 3KHz, an output amplitude of 14KV, a pulse rise time and a pulse fall time of 100ns; the catalyst in the dielectric barrier discharge reactor is a spherical magnesium chloride catalyst, the catalyst surface temperature is 700K, and the mixed gas flow rate is 90mL / min.

[0076] After testing, the NH at the gas outlet of the synthetic ammonia device 3 The concentration reaches 17500ppm.

[0077] Example 3

[0078] A method for synthesizing ammonia comprises the following steps:

[0079] A mixed gas of nitrogen and hydrogen in a volume ratio of 2:1 is heated to 250°C and flows evenly into a microwave coaxial resonant cavity, forming an atmospheric pressure nitrogen and hydrogen microwave discharge plasma at the opening of the microwave coaxial resonant cavity. The ejected microwave discharge plasma enters a dielectric barrier discharge reactor, and the microwave discharge plasma and the plasma generated in the dielectric barrier discharge reactor work together, and under the action of the catalyst in the dielectric barrier discharge reactor, ammonia synthesis is achieved;

[0080] The dielectric barrier discharge reactor is excited by a nanosecond pulse power supply with a frequency of 5KHz, an output amplitude of 10KV, a pulse rise time and a pulse fall time of 150ns;

[0081] The catalyst in the dielectric barrier discharge reactor is a spherical magnesium chloride catalyst, the catalyst surface temperature is 700K, and the mixed gas flow rate is 90mL / min.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A device for synthesizing ammonia, characterized in that: include: A microwave power supply, a microwave backflow prevention device, a three-pin dispenser, a microwave coaxial resonant cavity, and a dielectric barrier discharge reactor are connected in sequence; The dielectric barrier discharge reactor is connected to a nanosecond pulse power supply, and a catalyst is filled inside the dielectric barrier discharge reactor; A nitrogen source and a hydrogen source are connected to a gas inlet of the microwave coaxial resonant cavity; The length of the microwave coaxial resonant cavity is set to an odd number of quarter wavelengths; The dielectric barrier discharge reactor is a plate-plate electrode structure, and high-voltage electrodes are arranged on the upper and lower inner sides of the dielectric barrier discharge reactor, and the high-voltage electrodes include an upper high-voltage electrode and a lower high-voltage electrode; The upper high-voltage electrode is connected to a nanosecond pulse power supply, and the lower high-voltage electrode is connected to a ground electrode; The dielectric barrier discharge reactor is arranged in a tubular furnace; an air heater is also arranged between the nitrogen source and the hydrogen source and the gas inlet of the microwave coaxial resonant cavity.

2. The device for synthesizing ammonia according to claim 1, characterized in that: The microwave backflow prevention device comprises a circulator and a water load, wherein the inlet section and the outlet end of the circulator are respectively connected to a microwave power supply and a three-pin distributor.

3. The device for synthesizing ammonia according to claim 1, characterized in that: The nitrogen source is a nitrogen cylinder, and the hydrogen source is a hydrogen cylinder; pressure reducing valves are respectively arranged on the outlet pipes of the nitrogen cylinder and the hydrogen cylinder, and flow meters are respectively arranged downstream of the pressure reducing valves.

4. The device for synthesizing ammonia according to claim 1, characterized in that: A flow equalizer is also arranged between the nitrogen source and the hydrogen source and the gas inlet of the microwave coaxial resonant cavity. The nitrogen source and the hydrogen source are connected to an air heater, and the air heater is connected to the flow equalizer and the gas inlet of the microwave coaxial resonant cavity in turn.

5. The device for synthesizing ammonia according to claim 1, characterized in that: A thermocouple thermometer is arranged in the air heater.

6. The device for synthesizing ammonia according to claim 1, characterized in that: The device for synthesizing ammonia also includes an infrared thermal imager, a gas chromatograph and a container containing sulfuric acid; The infrared thermal imager is connected to the gas outlet of the dielectric barrier discharge reactor, and the infrared thermal imager is connected to the gas chromatograph and the container filled with sulfuric acid in sequence.

7. The device for synthesizing ammonia according to claim 1, characterized in that: The device for synthesizing ammonia also includes a Rogowski coil, an oscilloscope and a computer; The Rogowski coil shown is located between the dielectric barrier discharge reactor and the ground electrode. The Rogowski coil is connected to an oscilloscope. One end of the oscilloscope is connected to a gas chromatograph, and the other end is connected to a computer.

8. A method for synthesizing ammonia, using the apparatus for synthesizing ammonia as claimed in claim 1, characterized in that: The steps include: A mixed gas of nitrogen and hydrogen forms an atmospheric pressure nitrogen and hydrogen microwave discharge plasma at the opening of the microwave coaxial resonant cavity; The atmospheric pressure nitrogen and hydrogen microwave discharge plasma generated works together with the plasma generated in the dielectric barrier discharge reactor, and under the synergistic effect of the catalyst in the dielectric barrier discharge reactor, ammonia synthesis is achieved.

9. The method for synthesizing ammonia according to claim 8, characterized in that: The microwave power supply is a 2.45 GHz microwave power supply; Alternatively, the frequency of the nanosecond pulse power supply is 0-15KHz, the output amplitude is 0-15KV, and the pulse rise time and pulse fall time are 50-500ns.

10. The method for synthesizing ammonia according to claim 8, characterized in that: The catalyst is magnesium chloride; Alternatively, the surface temperature of the catalyst is 700°C, Alternatively, the gas temperature is 200°C Alternatively, the flow rate of the gas is 90 mL / min.

11. The method for synthesizing ammonia according to claim 8, characterized in that: The catalyst is a spherical magnesium chloride catalyst.

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