CN114205986A - Magnetically enhanced microwave plasma nitrogen fixation method and device - Google Patents
Magnetically enhanced microwave plasma nitrogen fixation method and device Download PDFInfo
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title claims abstract description 88
- 229910052757 nitrogen Inorganic materials 0.000 title claims abstract description 43
- 238000000034 method Methods 0.000 title claims abstract description 22
- 239000007789 gas Substances 0.000 claims abstract description 82
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 58
- 230000005540 biological transmission Effects 0.000 claims abstract description 53
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims abstract description 32
- 229910021529 ammonia Inorganic materials 0.000 claims abstract description 28
- 239000011797 cavity material Substances 0.000 claims description 90
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- 229910000831 Steel Inorganic materials 0.000 claims description 14
- 239000010959 steel Substances 0.000 claims description 14
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 12
- 239000001257 hydrogen Substances 0.000 claims description 12
- 229910052739 hydrogen Inorganic materials 0.000 claims description 12
- 239000007787 solid Substances 0.000 claims description 12
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- 239000010949 copper Substances 0.000 claims description 10
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- 238000003786 synthesis reaction Methods 0.000 claims description 7
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 claims description 6
- 230000002194 synthesizing effect Effects 0.000 claims description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 5
- 239000001301 oxygen Substances 0.000 claims description 5
- 229910052760 oxygen Inorganic materials 0.000 claims description 5
- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical group [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 4
- 229910052582 BN Inorganic materials 0.000 claims description 4
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 claims description 4
- 239000000919 ceramic Substances 0.000 claims description 4
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- 238000006243 chemical reaction Methods 0.000 abstract description 13
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- 238000003199 nucleic acid amplification method Methods 0.000 abstract 1
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- 244000005700 microbiome Species 0.000 description 2
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- IGLNJRXAVVLDKE-UHFFFAOYSA-N rubidium atom Chemical compound [Rb] IGLNJRXAVVLDKE-UHFFFAOYSA-N 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 239000010409 thin film Substances 0.000 description 2
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- 229910010413 TiO 2 Inorganic materials 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
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- 229910045601 alloy Inorganic materials 0.000 description 1
- 125000004429 atom Chemical group 0.000 description 1
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- 125000004433 nitrogen atom Chemical group N* 0.000 description 1
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 1
- YPJKMVATUPSWOH-UHFFFAOYSA-N nitrooxidanyl Chemical compound [O][N+]([O-])=O YPJKMVATUPSWOH-UHFFFAOYSA-N 0.000 description 1
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- 238000005507 spraying Methods 0.000 description 1
- 238000000629 steam reforming Methods 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
- H05H1/00—Generating plasma; Handling plasma
- H05H1/24—Generating plasma
- H05H1/46—Generating plasma using applied electromagnetic fields, e.g. high frequency or microwave energy
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C1/00—Ammonia; Compounds thereof
- C01C1/02—Preparation, purification or separation of ammonia
- C01C1/04—Preparation of ammonia by synthesis in the gas phase
- C01C1/0405—Preparation of ammonia by synthesis in the gas phase from N2 and H2 in presence of a catalyst
- C01C1/0417—Preparation of ammonia by synthesis in the gas phase from N2 and H2 in presence of a catalyst characterised by the synthesis reactor, e.g. arrangement of catalyst beds and heat exchangers in the reactor
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
- H05H1/00—Generating plasma; Handling plasma
- H05H1/24—Generating plasma
- H05H1/2406—Generating plasma using dielectric barrier discharges, i.e. with a dielectric interposed between the electrodes
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- Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Chemistry (AREA)
- Electromagnetism (AREA)
- Analytical Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Physical Or Chemical Processes And Apparatus (AREA)
Abstract
The invention discloses a magnetically enhanced microwave plasma nitrogen fixation method and a device. Wherein the outer layer gas discharge cavity is a plasma generation area, and a nitrogen fixation reaction area is formed after working gas is filled through the upper and lower ventilation holes. One end of the nitrogen fixation device is connected with the microwave source system through a microwave transmission line joint, and the other end is a microwave short-circuit port. Microwave energy generated by a microwave source system is transmitted into the inner microwave transmission cavity through the microwave transmission line joint, enters the gas discharge cavity through the inner pipe wall to excite working gas, and continuously generates uniform plasma in a surface wave discharge mode, so that a nitrogen fixation reaction is generated. According to the coaxial-structure microwave discharge nitrogen fixation reactor, the microwave transmission area and the gas discharge area are separated in parallel by designing the coaxial double-layer structure, the environment adaptability is good, nitrogen oxide or ammonia can be directly and efficiently generated, the structure is simple, the operation is convenient and fast, and the amplification is easy.
Description
Technical Field
The invention belongs to the field of chemical nitrogen fixation research, and particularly relates to a magnetically enhanced microwave plasma nitrogen fixation method and a device.
Background
Ammonia (NH)3) Is an inorganic compound with a simple molecular structure, but is widely applied to the industries of agriculture, food, pharmacy and war industry, and is an intermediate chemical product related to civil life. Ammonia is not only a resource, has the advantages of environmental protection, easy storage and transportation and the like, is a well-known chemical carrier of hydrogen energy, has special advantages in the aspects of hydrogen storage and transportation, hydrogen supply and hydrogen replacement, is regarded as a liquid energy source and can be called as ammonia energy. Because of concerns about civil life and development, the demand of synthetic ammonia products is extremely large globally, and for a long time, synthetic ammonia is an inorganic chemical product with the highest yield in the world, and is produced by about 1.75 million tons every year in the world, while China is the largest industrial production country of synthetic ammonia, and the annual yield reaches 8000 ten thousand tons. The synthetic ammonia industry starts at 20In the early century, FritzHaber and CarlBosch, German scientists, combined, developed synthetic ammonia technology. The Haber-Bosch process is a process of generating H2 by steam reforming, separating N2, H2 and N2 from air by a low temperature process under high temperature and pressure reaction conditions to gradually form NH3 on the surface of a catalyst, and converting N2 in the atmosphere into ammonia which can be absorbed by crops, which can be considered as an artificial nitrogen fixation method. Although the Haber-Bosch process has been developed for hundreds of years, the process always starts from air preparation of N2 and steam recombination preparation of H2, the synthesis reaction of ammonia still needs to be carried out under the conditions of high temperature and high pressure, and the problems of energy consumption, pollution, safety and the like exist. Practical results prove that the problems are solved only by optimizing the Haber-Bosch process, and the synthetic ammonia industry is difficult to get rid of the properties of high energy consumption, high temperature, high pressure, high risk and high pollution.
Low temperature plasma technology is widely used in the material preparation and processing industry. The low-pressure plasma is generally low in temperature, has extremely high particle effect and chemical effect, and has good application in the aspects of low-temperature film deposition, material surface modification and the like. The arc plasma belongs to an important classification of low-temperature plasma sources, is plasma in a local thermal equilibrium state, has the characteristics of high current density, high gas temperature (3000K-30000K), concentrated energy, low maintenance voltage, wide variety of working gases and the like, and is widely applied to the technical processes which cannot be finished by a plurality of conventional methods such as metal cutting, welding, smelting, spraying, particle spheroidizing, dielectric material processing and the like. Microwave plasma has its unique characteristics: no electrode, environment friendliness, wide working pressure range, wide temperature range and the like, and the method has attracted increasingly wide attention in the aspects of high-purity thin film material preparation, high-purity material treatment and the like.
The technology for synthesizing ammonia by utilizing photocatalysis, photoelectrocatalysis and electrocatalysis nitrogen reduction is a research hotspot of various national scholars. As early as 1977, Schrauzer et al discovered that a semiconductor TiO 2-based photocatalyst had the effect of catalyzing nitrogen reduction to synthesize ammonia under ultraviolet irradiation. The photocatalytic nitrogen reduction process is limited by the diffusion and separation of photoelectrons and carriers, and the research on the photocatalyst is mostly carried out throughThe appearance and defect design of the catalyst shortens the diffusion distance of current carriers and reduces the opportunity of photoelectron and hole recombination. The photoelectrocatalysis technology can directly convert solar energy into chemical energy, and is a promising method for reducing the energy consumption of the ammonia synthesis industry, but the most important problem is the lack of NRR catalyst with high Faraday efficiency. Is generally obtained by ionizing N2 by conventional methods
The required electron energy is up to 15.6eV, the electron energy required to obtain N atoms by dissociation is also 9.75eV, the electron energy required for electron excitation of N2 is 6.17eV, and the excited state can be obtained by particle collision excitation of N2
The energy required is only 0.29 eV. In fact, since the dissociation energy of the first N-N bond of the N-N bond is as high as 410 kJ.mol-1, under the mild conditions we pursued, the electronic energy in photocatalysis and electrocatalysis is not sufficient to directly destroy the N-N bond, usually by undergoing alternate or terminal associations, which is then broken after N-H formation.
Plasma technology has been applied to various fields because of its own characteristics. The plasma is composed of a large number of ions, electrons, excited atoms, free radicals and other high-activity particles, and has strong chemical activity. The traditional chemical method needs to improve the reaction rate by increasing the reaction temperature and the reaction pressure, while the electron temperature in the low-temperature plasma is very high, the ion and molecule temperature is very low and is close to the normal temperature, the thermodynamic nonequilibrium is formed, and the characteristic enables the low-temperature plasma to have high electron energy and lower ion and gas temperature, so that certain thermodynamically difficult reactions can be carried out at the normal temperature and the normal pressure, and high-energy electrons can be provided for N2 activation.
Currently, the mainstream method for synthesizing ammonia is an HB method using nitrogen and hydrogen, but the HB method requires high temperature, high pressure and a catalyst, and also consumes a large amount of secondary energy such as electricity and steam in the whole production process, so that the energy consumption accounts for about 3% of the world energy consumption, and a large amount of wastewater, waste gas and waste residues are discharged in the production process. Biological nitrogen fixation is a special physiological function of nitrogen-fixing microorganisms, but the yield is limited, and most of the nitrogen-fixing microorganisms are still in a theoretical stage. Shigeyuki Thnaka et al, university of Aoyama Gakuin dissociates and excites nitrogen and hydrogen with radio frequency and microwave plasma, combines to generate ammonia under the catalytic action of iron wire coils, and has low efficiency and high energy consumption. Duy Khoe Dinh et al use sliding arc in combination with dielectric barrier discharge to fix nitrogen, and the energy consumption of nitrate radical products is 8MJ/mol, which is more than one order of magnitude higher than that of the mature HB method.
Disclosure of Invention
Aiming at the defects of extreme environmental requirements and high preparation energy consumption of the existing nitrogen fixation method, the invention provides a magnetically enhanced microwave plasma nitrogen fixation method and a device, the method and the device can meet the requirements of a pressure range of 10Pa-10atm and a temperature range of room temperature-30000K, have multiple functions (thin film material preparation and powder processing functions, compound and alloy manufacture, and direct and efficient synthesis of nitric oxide and ammonia), and can be used for implementing a material surface treatment technology in a long distance, and the invention has the outstanding characteristics of wide working pressure range (10Pa-10atm), no need of an igniter or ultraviolet rays, lasers and plasma pre-ionization technologies, high material preparation space purity, wide application range, simple structure and easy popularization, and wide allowable plasma core temperature range (room temperature-30000K). The resonance heating effect of the magnetic field on electrons is fully utilized, the nitrogen fixation efficiency of the plasma is improved, the high-temperature and high-pressure catalyst required by HB is avoided, and the cost of ammonia synthesis is reduced.
The technical scheme adopted by the invention is as follows:
a magnetic enhancement microwave plasma device is characterized in that an inner layer of the magnetic enhancement microwave plasma device is an inner microwave transmission cavity (2), an outer layer of the magnetic enhancement microwave plasma device is an outer gas discharge cavity (1), and a resonant magnetic field generating component is arranged outside the discharge cavity;
the periphery of the outer layer gas discharge cavity (1) is cylindrical, the outer layer gas discharge cavity (1) is coaxial with the inner layer microwave transmission cavity (2), and the outer layer gas discharge cavity (1) surrounds the periphery of the inner layer microwave transmission cavity (2); both sides of the outer layer gas discharge cavity (1) are respectively provided with an upper scavenging hole and a lower scavenging hole; the outer layer gas discharge cavity (1) is a plasma generation area, and a discharge medium is formed after working gas is filled through the upper scavenging hole and the lower scavenging hole;
one end of the magnetic enhanced microwave plasma device is inserted into a microwave transmission line joint (8) through a connecting seat to be connected with a microwave source system, and the other end of the magnetic enhanced microwave plasma device is provided with a microwave short-circuit port (6).
Further, microwave energy generated by a microwave source system is transmitted into the inner microwave transmission cavity (2) through the microwave transmission line joint (8), enters the outer gas discharge cavity (1) through the wall of the inner microwave transmission cavity to excite working gas, uniform plasma is continuously generated through a surface wave discharge mode, and then synthesis of nitrogen-containing components is generated; preferably, the nitrogen-containing component is nitrogen oxide or ammonia; preferably, the working gas is a nitrogen and hydrogen mixed gas for directly synthesizing ammonia or a nitrogen and oxygen mixture for generating nitrogen oxides; preferably the gas pressure inside the discharge chamber (1) may be 10Pa to 10000Pa, or atmospheric pressure (1atm), overpressure (1-10 atm).
Further, the cavity material of the outer layer gas discharge cavity is quartz glass, or the inner wall of the outer layer gas discharge cavity is made of a microwave transmission material. The outer layer of the gas discharge cavity is made of alumina ceramic or boron nitride ceramic; preferably, the cavity material of the outer layer gas discharge cavity is quartz with purity of more than 99.99%.
Furthermore, the outer gas discharge cavity (1) is a lamp tube with an outer gas discharge cavity, the lamp tube structure is a hollow double-layer quartz tube structure, or a copper inner conductor (3) is additionally arranged on the inner layer of the lamp tube, or a copper net is additionally arranged outside the lamp tube, or an iron net or a nickel net (10) is additionally arranged inside the lamp tube, and gas is introduced into the inner layer between the copper inner conductor and the outer gas discharge cavity for cooling.
The inner layer of the magnetic enhanced microwave plasma device is a microwave transmission cavity, the outer layer of the magnetic enhanced microwave plasma device is a gas discharge cavity, and a resonant magnetic field generating component formed by a permanent magnet steel array is arranged outside the discharge cavity; the outer layer gas discharge cavity is a cavity formed by quartz glass, the periphery of the outer layer gas discharge cavity is cylindrical, is coaxial with the inner layer microwave transmission cavity and surrounds the periphery of the inner layer microwave transmission cavity; the outer layer gas discharge cavity is a plasma generation area, and working gas with certain pressure is filled through the upper and lower ventilation holes to form a discharge medium; one end of the device is inserted into a microwave transmission line joint through a connecting seat to be connected with a microwave source system, and the other end of the device is a microwave short-circuit port; microwave energy generated by a microwave source system is transmitted into an inner microwave transmission cavity through a microwave transmission line joint, enters a gas discharge cavity through the inner pipe wall to excite working gas, continuously generates uniform plasma in a surface wave discharge mode, and then generates synthesis of nitrogen-containing components, such as nitrogen oxide or ammonia; the working gas is a mixed gas of nitrogen and hydrogen for directly synthesizing ammonia, or a mixture of nitrogen and oxygen for generating nitrogen oxide; the gas pressure in the discharge cavity can be 10Pa to 10000Pa, or normal pressure (1atm) and over-normal pressure (1-10 atm).
Furthermore, the outer layer gas discharge cavity is made of quartz glass, and the cavity material is quartz with purity of more than 99.99%, or the inner layer is made of microwave transmission material and has higher melting point, such as alumina ceramic and boron nitride ceramic.
Furthermore, the structure of the outer layer gas discharge cavity lamp tube is a hollow double-layer quartz tube structure, or a copper inner conductor is additionally arranged on the inner layer, or a copper net and an iron net are additionally arranged outside or inside the lamp tube, and gas is introduced into the inner layer for cooling.
Furthermore, the microwave source system is a magnetron microwave source or a solid state microwave source, the system frequency is 0.915GHz or 2.45GHz or the frequency within the frequency band of 2.45-30GHz, and the sizes of the discharge cavity and the microwave transmission line joint are matched with the frequency. Furthermore, the magnetron microwave source comprises a microwave power supply with a cooling system, the microwave power supply is connected to the magnetron to emit microwave signals, the microwave power supply is connected to a microwave transmission line through a rectangular waveguide in a transmission mode, and three pins can be selectively installed on the rectangular waveguide to be adjusted.
Furthermore, the resonance magnetic field generating component is a permanent magnet steel array or a water-cooling magnetic field coil, and the intensity of the resonance magnetic field generating component can generate an electron cyclotron resonance surface in a discharge area.
Furthermore, the magnetically enhanced microwave plasma is linearly amplified by additionally arranging a power divider in a microwave source system.
The invention also provides a magnetically enhanced microwave plasma nitrogen fixation method using the device.
By the scheme, the invention at least has the following advantages:
the invention adopts a microwave electrodeless discharge mode, and the microwave energy directly excites the working gas, thereby avoiding the problems of complex structure, limited gas types, limited application range and the like caused by using a radio frequency or microwave resonant cavity; through the coaxial double-deck discharge cavity of design, keep apart microwave transmission chamber and discharge chamber parallel, the microwave sees through transmission chamber medium and forms powerful surface electric field on the pipe wall in discharge chamber, and the mode through surface wave discharge produces plasma, is favorable to forming the plasma of even stable discharge, produces the solid nitrogen reaction then, increases solid nitrogen efficiency with electron cyclotron resonance magnetic field, and this structure accessible power divider is linear to be enlargies simultaneously. The invention has simple structure, good environmental adaptability, convenient operation and easy realization of industrialization.
Drawings
Fig. 1 is a schematic structural diagram of an embodiment of a magnetically enhanced microwave plasma nitrogen fixation method provided by the invention.
In the figure, 1 outer layer gas discharge cavity, 2 inner layer microwave transmission cavity, 3 inner conductor, 4 upper air exchanging pipe, 5 lower air exchanging pipe, 6 microwave short circuit port, 7 polytetrafluoroethylene pad, 8 transmission line joint, 9 permanent magnet steel array or excitation coil, 10 iron net or nickel net.
Detailed Description
The technical solution in the embodiments of the present invention is clearly and completely described below with reference to the drawings and the embodiments.
Examples
The following detailed description of specific embodiments of the present invention will be made with reference to the accompanying drawings and examples. The following examples are intended to illustrate the invention, but are not intended to limit the scope of the invention.
Fig. 1 shows a schematic structural diagram of a magnetically enhanced microwave plasma nitrogen fixation system of the present invention, which includes a coaxial double-layer discharge tube, and includes an outer gas discharge cavity 1, where the outer gas discharge cavity 1 is a cavity formed by high-purity (purity greater than 99.99%) quartz glass, and the periphery of the outer gas discharge cavity is cylindrical, is coaxial with an inner microwave transmission cavity 2, and surrounds the periphery of the inner microwave transmission cavity 2. The outer gas discharge chamber 1 is a plasma generation region.
The outer layer gas discharge cavity 1 is a lamp tube of the outer layer gas discharge cavity and has a hollow double-layer quartz tube structure.
Optionally, a copper bar inner conductor 3 is additionally arranged in the inner-layer microwave transmission cavity 2 and is fixed through a polytetrafluoroethylene cushion seat 7. An upper scavenging tube 4 and a lower scavenging tube 5 are arranged on two sides of the discharge tube, two ends of the lamp tube are respectively connected with a microwave short-circuit port 6 and a transmission line joint 8 which is connected with the microwave source system, and the transmission line joint 8 is inserted into the transmission line joint through a connecting seat to be connected with the microwave source system. Two ends of the discharge tube are respectively provided with a microwave short-circuit port and a connecting seat, and a permanent magnet steel array or an excitation coil 9 is arranged outside.
The invention forms a discharge medium after filling working gas through the upper scavenging tube 4 and the lower scavenging tube 5.
The microwave source system is a magnetron microwave source or a solid state microwave source, the frequency of the system is within the frequency band of 0.915GHz, 2.45GHz or 2.4530GHz, and the sizes of the lamp tube and the microwave transmission line joint are matched with the frequency. The magnetron microwave source comprises a microwave power supply with a cooling system, is connected to a magnetron to emit microwave signals, is connected to a microwave transmission line through a rectangular waveguide in a transmission way, and can be selectively provided with three pins for adjustment.
The permanent magnet steel array or the exciting coil 9 is a magnetic field generating unit. The magnetic field generating unit is used for generating a magnetic field required by electron cyclotron resonance and enhancing the reaction efficiency. Wherein, the excitation coil can be a water-cooling magnetic field coil. An iron net or a nickel net 10 is arranged in the discharge tube, and a copper net is arranged outside the discharge tube. Microwave energy emitted by a magnetron microwave source or a solid microwave source system in the microwave is fed into an inner microwave transmission cavity 2 of the double-layer lamp tube through a transmission line joint 8, enters an outer gas discharge cavity 1 through the tube wall of the inner microwave transmission cavity 2 to excite working gas to generate plasma and further generate products for fixing nitrogen, and the unabsorbed microwave energy is reflected to the cavity by a microwave short circuit port. And gas is introduced into the inner microwave transmission cavity 2 for cooling.
Reaction gas N2/H2Or N2/O2Enters the outer gas discharge cavity 1 from the upper scavenging tube 4, and flows out from the lower scavenging tube 5 after nitrogen fixation reaction.
The inner and outer structural materials of the outer gas discharge chamber 1 in the figure are high-purity quartz glass, because the quartz glass is a high-microwave-transmittance material and a high-ultraviolet-transmittance material. According to the design principle of the invention, the requirement of the invention is met only by the inner layer being made of high microwave transmittance material and the outer layer being made of high temperature resistant material. For example, the high-temperature resistant material is alumina ceramic, boron nitride ceramic or the like. The magnetically enhanced microwave plasma system is linearly amplified by additionally arranging a power divider in a microwave source system.
According to the magnetically enhanced microwave plasma nitrogen fixation system, the microwave transmission area and the gas discharge area are separated in parallel by designing the coaxial double-layer structure, uniform plasma is generated through surface wave discharge, and then nitrogen fixation reaction is generated. Optionally, a nitrogen-containing component, such as nitrogen oxide or ammonia, is produced by the nitrogen fixation reaction; the working gas is a mixed gas of nitrogen and hydrogen for directly synthesizing ammonia, or a mixture of nitrogen and oxygen for generating nitrogen oxide; the gas pressure in the discharge cavity can be 10Pa to 10000Pa, or normal pressure (1atm) and over-normal pressure (1-10 atm).
In one embodiment of the invention, a magnetically enhanced microwave plasma nitrogen fixation device is installed, a permanent magnet steel array 9 is formed by arranging and combining rubidium, iron and boron N45, the magnetic field intensity on the surface of magnetic steel is about 3000 gauss, the distance of the magnetic steel is adjusted to enable the permanent magnet steel array to form a 875 gauss magnetic field in an outer layer discharge cavity 1, and the magnetic lines of force are axially parallel to the outer layer discharge cavity; connecting the solid state microwave source system with a transmission line connector 8; connecting a ventilation pipe 4 and a gas supply system, wherein the gas supply system is used for introducing nitrogen and oxygen (or nitrogen and hydrogen) in a fixed ratio through a mass flow controller (N2: O2 is 1: 2); connecting a lower air exchange tube 5 and a vacuum pump, and adjusting the air pressure in the outer layer discharge cavity 1 to 10Pa through the vacuum pump; setting the power of a solid microwave source to be 300W, starting the solid microwave source, and adjusting the air pressure in the outer layer discharge cavity 1 to 10kPa after plasma is generated in the outer layer discharge cavity 1; the nitrogen gas is subjected to dissociation reaction and ionization under the action of the plasma and rapidly carries out chemical reaction with oxygen gas which is also subjected to dissociation and ionization, and nitrogen oxides are efficiently and rapidly generated and discharged from the lower air exchange pipe 5 and the vacuum pump.
In one embodiment of the invention, a magnetically enhanced microwave plasma nitrogen fixation device is installed, a permanent magnet steel array 9 is formed by arranging and combining rubidium, iron and boron N45, the magnetic field intensity on the surface of magnetic steel is about 3000 gauss, the distance of the magnetic steel is adjusted to enable the permanent magnet steel array to form a 875 gauss magnetic field in an outer layer discharge cavity 1, and the magnetic lines of force are axially parallel to the outer layer discharge cavity; connecting the solid state microwave source system with a transmission line connector 8; connecting an upper air exchange tube 4 and an air supply system, wherein the air supply system is used for introducing nitrogen and hydrogen in a fixed ratio (N2: H2 is 1: 3) through a mass flow controller; connecting a lower air exchange tube 5 and a vacuum pump, and adjusting the air pressure in the outer layer discharge cavity 1 to 10Pa through the vacuum pump; setting the power of a solid microwave source to be 300W, starting the solid microwave source, and adjusting the air pressure in the outer layer discharge cavity 1 to 10kPa after plasma is generated in the outer layer discharge cavity 1; the nitrogen gas is subjected to dissociation reaction and ionization under the action of the plasma, and rapidly and chemically reacts with the hydrogen gas which is subjected to dissociation and ionization, so that the ammonia is efficiently and rapidly generated and is discharged from the lower scavenging pipe 5 and the vacuum pump.
The invention has not been described in detail and is part of the common general knowledge of a person skilled in the art. Although illustrative embodiments of the present invention have been described above to facilitate the understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the embodiments, and it will be apparent to those skilled in the art that various changes may be made without departing from the spirit and scope of the invention as defined and defined by the appended claims, and all matter which comes within the scope of the inventive concept is protected.
Claims (9)
1. A magnetically enhanced microwave plasma device, characterized by: the inner layer of the magnetic enhanced microwave plasma device is an inner microwave transmission cavity (2), the outer layer is an outer gas discharge cavity (1), and a resonant magnetic field generating component is arranged outside the discharge cavity;
the periphery of the outer layer gas discharge cavity (1) is cylindrical, the outer layer gas discharge cavity (1) is coaxial with the inner layer microwave transmission cavity (2), and the outer layer gas discharge cavity (1) surrounds the periphery of the inner layer microwave transmission cavity (2); both sides of the outer layer gas discharge cavity (1) are respectively provided with an upper scavenging hole and a lower scavenging hole; the outer layer gas discharge cavity (1) is a plasma generation area, and a discharge medium is formed after working gas is filled through the upper scavenging hole and the lower scavenging hole;
one end of the magnetic enhanced microwave plasma device is inserted into a microwave transmission line joint (8) through a connecting seat to be connected with a microwave source system, and the other end of the magnetic enhanced microwave plasma device is provided with a microwave short-circuit port (6).
2. A magnetically enhanced microwave plasma device according to claim 1, wherein: microwave energy generated by a microwave source system is transmitted into an inner microwave transmission cavity (2) through a microwave transmission line joint (8), enters an outer gas discharge cavity (1) through the wall of the inner microwave transmission cavity to excite working gas, and generates uniform plasma continuously in a surface wave discharge mode, so that the synthesis of nitrogen-containing components is generated; preferably, the nitrogen-containing component is nitrogen oxide or ammonia; preferably, the working gas is a nitrogen and hydrogen mixed gas for directly synthesizing ammonia or a nitrogen and oxygen mixture for generating nitrogen oxides; preferably the gas pressure inside the discharge chamber (1) may be 10Pa to 10000Pa, or atmospheric pressure (1atm), overpressure (1-10 atm).
3. A magnetically enhanced microwave plasma device according to claim 1, wherein: the cavity material of the outer layer gas discharge cavity is quartz glass, or the inner wall of the outer layer gas discharge cavity is made of a microwave transmission material; preferably, the outer layer of the gas discharge cavity is alumina ceramic or boron nitride ceramic; preferably, the cavity material of the outer layer gas discharge cavity is quartz with purity of more than 99.99%.
4. A magnetically enhanced microwave plasma device according to claim 1, wherein: the outer gas discharge cavity (1) is a lamp tube with an outer gas discharge cavity, the lamp tube structure is a hollow double-layer quartz tube structure, or a copper inner conductor (3) is additionally arranged on the inner layer of the lamp tube, or a copper net is additionally arranged outside the lamp tube, or an iron net or a nickel net (10) is additionally arranged inside the lamp tube, and gas is introduced into the inner layer between the copper inner conductor and the outer gas discharge cavity for cooling.
5. A magnetically enhanced microwave plasma device according to claim 1, wherein: the microwave source system is a magnetron microwave source or a solid state microwave source, the frequency of the system is within the frequency band of 0.915GHz, 2.45GHz or 2.4530GHz, and the sizes of the lamp tube and the microwave transmission line joint are matched with the frequency.
6. A magnetically enhanced microwave plasma device according to claim 4, wherein: the magnetron microwave source comprises a microwave power supply with a cooling system, is connected to a magnetron to emit microwave signals, is connected to a microwave transmission line through a rectangular waveguide in a transmission way, and can be selectively provided with three pins for adjustment.
7. A magnetically enhanced microwave plasma device according to claim 1, wherein: the resonance magnetic field generating component is a permanent magnet steel array or a water-cooling magnetic field coil, and the intensity of the resonance magnetic field generating component can generate an electron cyclotron resonance surface in a discharge area.
8. A magnetically enhanced microwave plasma device according to claim 1, wherein: the magnetically enhanced microwave plasma is linearly amplified by additionally arranging a power divider in a microwave source system.
9. A magnetically enhanced microwave plasma nitrogen fixation method, characterized in that the device according to any of claims 1-8 is used.
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