Capillary array packed bed micro-discharge nitrogen fixation device
By filling a capillary array into a dielectric barrier discharge device, the problems of randomness and low energy density of micro-discharge are solved, achieving efficient nitrogen treatment and low-energy nitrogen fixation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DALIAN UNIV OF TECH
- Filing Date
- 2026-04-15
- Publication Date
- 2026-06-05
AI Technical Summary
The efficiency of existing dielectric barrier discharge nitrogen fixation devices is low because of low energy density and the random generation of micro-discharges in space, which limits the nitrogen treatment time and total amount.
By filling a coaxial cylindrical dielectric barrier discharge device with a capillary array, multiple small-area discharges are formed, which restricts micro-discharges from occurring inside the capillaries and in the gaps, thereby improving energy density and processing time.
It significantly improves the dissociation efficiency of nitrogen and oxygen, enhances the generation of nitrogen oxides, reduces energy consumption, has a simple structure and low cost, and is suitable for distributed production.
Smart Images
Figure CN122160985A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of plasma science and relates to a capillary array packed bed micro-discharge nitrogen fixation device. Background Technology
[0002] Nitrogen is a core element of biological macromolecules such as proteins, nucleic acids, and chlorophyll, and is one of the essential elements for maintaining life activities. Nitrogen fixation is the process of converting inert nitrogen gas in the atmosphere into nitrogen-containing compounds that can be used by organisms, and is mainly divided into natural nitrogen fixation and artificial nitrogen fixation. However, with population growth and industrial development, natural nitrogen fixation can no longer meet the needs, thus requiring artificial nitrogen fixation. The Haber-Bosch (HB) process is one of the most important methods of artificial nitrogen fixation. Its core principle is to react nitrogen and hydrogen gas on the surface of an iron-based catalyst under high temperature and pressure to produce ammonia gas. About 50% of global food production depends on nitrogen fertilizer produced by this method. However, the HB process also has its drawbacks. First, it is energy-intensive and polluting, consuming about 1-2% of global energy and emitting 1% of global greenhouse gases annually; second, the reaction conditions are harsh, requiring 450-500℃ and 15-25MPa to ensure a high reaction rate; third, the reaction process is complex, the equipment occupies a large area, and start-up and shutdown are complicated, requiring large-scale centralized production.
[0003] Low-temperature plasma nitrogen fixation is one of the green nitrogen fixation methods that has the potential to replace the HB method. The theoretical energy consumption of low-temperature plasma nitrogen fixation is as low as 0.2 MJ / mol, and it can be combined with green electricity to achieve near-zero emissions, showing great application potential. Dielectric barrier discharge is a discharge method that can generate low-temperature plasma at room temperature and pressure. In dielectric barrier discharge, when the applied voltage is higher than the Paschen breakdown voltage, a large number of randomly distributed micro-discharges appear in the discharge space. The discharge channels of these micro-discharges are basically cylindrical, with a radius of about 0.1~0.3 mm. The discharge time is extremely short, but the current density is very high, which is one of the important reasons for the generation of active particles. However, the reported efficiency of catalyst-free dielectric barrier discharge nitrogen fixation is still very low, for the following reasons: First, the energy density of dielectric barrier discharge is low, while breaking the nitrogen-nitrogen triple bond in nitrogen gas requires 9.75 eV; second, the micro-discharges are generated randomly in space, which limits the processing time and total amount of gas molecules processed by the discharge. Summary of the Invention
[0004] To address the aforementioned problems, this invention provides a capillary array-filled bed micro-discharge nitrogen fixation device. This device enhances micro-discharge by filling a coaxial cylindrical dielectric barrier discharge chamber with a capillary array, significantly increasing the discharge energy and quantity, promoting the dissociation of nitrogen and oxygen, and thus improving the efficiency of plasma nitrogen fixation.
[0005] The technical solution of the present invention is as follows: A capillary array packed bed micro-discharge nitrogen fixation device includes a rod-shaped electrode, an insulating shell, a capillary array, a grounding electrode, and an insulating plug.
[0006] The insulating shell is a hollow cylindrical structure, and the rod-shaped electrode is a conductive electrode that axially penetrates the center of the insulating shell and is fixed at both ends by two insulating plugs. The capillary array is arranged in a concentric circle between the outer surface of the rod-shaped electrode and the inner wall of the insulating shell. The side of the insulating plug is provided with through holes, which serve as gas inlets and outlets, respectively, and are connected to an external gas source. Gas flows only through the gas inlet, the gap between the capillaries, and the gas outlet. The grounding electrode covers the outer wall of the insulating shell, wrapping the insulating shell around its circumference.
[0007] The rod-shaped electrode is connected to an external power supply, and the power supply voltage amplitude, frequency, and waveform are adjustable.
[0008] The power supply is pulse, power frequency AC, or high frequency AC. The pulse power supply is a bipolar pulse power supply with a frequency of 25Hz to 200Hz and a peak value of 10kV to 25kV. The power frequency AC power supply has an amplitude of 10kV to 25kV. The high frequency AC power supply has a frequency of 5kHz to 14kHz and an amplitude of 10kV to 25kV.
[0009] The rod-shaped electrode is made of cylindrical conductive material, such as stainless steel or tungsten. The electrode surface has threads or dot-like protrusions. The thread pitch is adjustable within 0.4 to 4 mm. The diameter of the protrusions is no higher than 1 mm, the height is no higher than 0.5 mm, and the distance between two protrusions is no greater than 1 mm.
[0010] The insulating shell is made of insulating media such as quartz or glass; the ratio of the inner diameter of the insulating shell to the length of the tube is 1:10 to 1:30, and the wall thickness is 0.5 to 2 mm; the inner diameter of the insulating shell is larger than the diameter of the rod electrode, and the length is shorter than the length of the rod electrode.
[0011] In the capillary array, the inner diameter of a single capillary is 10μm~1000μm, the wall thickness is 100μm, and the length is the same as or slightly shorter than the insulating shell; the capillary is made of a dielectric material with a relative permittivity between 1 and 10.
[0012] The grounding electrode is mesh, strip, or sheet-like, and is made of a conductor material capable of withstanding currents of 50A or higher. The mesh size of the mesh grounding electrode is not less than 60 meshes, and the thickness of the strip or sheet-like grounding electrode is not more than 0.5mm. The length of the grounding electrode is shorter than that of the insulating shell; the ratio of the grounding electrode length to the capillary array length is not less than 1:5.
[0013] The insulating plug can withstand a bipolar pulse voltage with a peak value of 50kV or an AC voltage with an amplitude of 50kV.
[0014] The gas flow rate of the external gas source ensures that the residence time of the gas in the capillary array is not less than 0.5 seconds. The external gas source is air or a mixture of nitrogen, oxygen, and rare gases, wherein the volume ratio of nitrogen in the mixture is not less than 5%.
[0015] The beneficial effects of this invention are: Based on a conventional coaxial cylindrical dielectric barrier discharge (DMD) device, a capillary array with an inner diameter on the micrometer scale is incorporated. Due to the addition of the capillary array, the discharge region is divided into multiple small areas, with the discharge occurring within the gaps between the capillaries. This results in high energy density for the micro-discharge and confinement of the micro-discharge to a small area. When gas flows through, the probability and processing time of nitrogen and oxygen molecules by the micro-discharge increase, thus generating more nitrogen and oxygen atoms, which are beneficial for the synthesis of nitrogen oxides. Compared to filling the DDM device with particulate matter, filling with a capillary array allows the gas to pass through the discharge region uniformly, enabling more thorough and uniform gas processing by the micro-discharge. This device allows for adjustment of the inner diameter of the incorporated capillaries according to the discharge characteristics of the introduced gas to achieve optimal nitrogen fixation, offering high flexibility. The device is simple in structure, easy to install, low in cost, and highly economical. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the capillary array packed bed micro-discharge nitrogen fixation device provided by the present invention.
[0017] Figure 2 This is a comparison curve of the discharge power of a micro-discharge nitrogen fixation device with a capillary array bed filled with 0.5mm inner diameter and a dielectric barrier discharge device without capillary filling.
[0018] Figure 3 This is a comparison of the nitrogen fixation energy consumption of a capillary array-filled bed micro-discharge nitrogen fixation device and a dielectric barrier discharge device without capillary filling under the same operating conditions.
[0019] In the diagram, 1 is a rod-shaped electrode; 2 is a left insulating plug; 3 is a gas inlet; 4 is an insulating shell; 5 is a capillary array; 6 is a grounding electrode; 7 is a right insulating plug; and 8 is a gas outlet. Detailed Implementation
[0020] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.
[0021] The capillary array packed bed micro-discharge nitrogen fixation device of the present invention, such as Figure 1 As shown, it includes a rod-shaped electrode 1, a left insulating plug 2, an insulating shell 4, a capillary array 5, a grounding electrode 6, and a right insulating plug 7.
[0022] The insulating shell 4 is a hollow cylindrical structure. The rod-shaped electrode 1 is a conductive electrode that axially penetrates the center of the insulating shell 4. Both ends are fixed by the left insulating plug 2 and the right insulating plug 7, with no gaps at the contact points to ensure the uniformity and sealing of the dielectric barrier discharge. The insulating shell 4 is a hollow cylindrical structure made of dielectric materials such as quartz or glass. The left insulating plug 2 and the right insulating plug 7 are made of insulating materials such as ABS. The capillary array 5 is arranged in a concentric circle array between the outer surface of the rod-shaped electrode 1 and the inner wall of the insulating shell 4. The sides of the left insulating plug 2 and the right insulating plug 7 are provided with through holes. The gas inlet 3 and the gas outlet 8 are respectively located on the left insulating plug 2 and the right insulating plug 8. The gas flow direction is gas inlet 3, capillary array 5, and gas outlet 8. The grounding electrode 6 covers the outer wall of the insulating shell 4 and can be in the form of a mesh or patch, and can be made of materials such as copper or stainless steel, forming a ring-shaped electric field during discharge. In actual operation, the discharge is mainly concentrated in the area of the capillary array 5 covered by the grounding electrode 6.
[0023] During operation, the power supply is first connected to the rod-shaped electrode 1, and the grounding wire is connected to the grounding electrode 6. Gas enters the insulating shell 4 through the inlet 3 and passes through the capillary array 5, then exits the device through the outlet 8. After applying a certain voltage, the capillary array 5 discharges. Due to the close arrangement of the capillary array, the large discharge space is divided into sub-millimeter-level discharge spaces. First, the micro-discharge is confined within and between the capillaries, eliminating the adverse effects of irregular micro-discharge on the generation of active particles. Second, an extremely high electric field is generated near the contact surface between the capillaries, and a large amount of micro-discharge is generated in the gaps, which is conducive to the large-scale generation of active particles. Moreover, filling the capillary array 5 allows the gas to pass through the discharge area uniformly, enabling the micro-discharge to process the gas more fully and uniformly.
[0024] The capillary array packed bed micro-discharge nitrogen fixation method of the present invention, using the above-mentioned apparatus, includes the following steps: S1: Introduce working gas to form a stable fluid in capillary array 5.
[0025] S2: Adjust the voltage waveform, amplitude, and frequency applied to the rod electrode 1 to generate a stable dielectric barrier discharge in the capillary array 5 region, resulting in a nitrogen fixation reaction.
[0026] S3: Absorb and measure the gas outside the exhaust device.
[0027] In this embodiment, the rod-shaped electrode has an inner diameter of 6 mm, the insulating shell has an inner diameter of 12 mm and an outer diameter of 14 mm, the grounding electrode has a length of 100 mm, the capillary has a length of 100 mm, an inner diameter of 0.5 mm, an outer diameter of 0.7 mm, and an air flow rate of 50 mL / min.
[0028] like Figure 2The figure shows a comparison of discharge power between a micro-discharge nitrogen fixation device with a capillary array bed filled with capillary tubes (0.5 mm inner diameter) and a dielectric barrier discharge device without capillary tubes. Under conditions of a pulsed power supply frequency of 50 Hz and a gas flow rate of 50 mL / min, varying the voltage amplitude by 12-20 kV, the power of the micro-discharge nitrogen fixation device with the capillary array was significantly higher than that without. Furthermore, the power difference increased with increasing voltage level; at 20 kV, the power of the device with capillary tubes was 4.44 W, while the power of the device without capillary tubes was 3.54 W. Adding 0.5 mm inner diameter capillary tubes increased the discharge power of the device by approximately 25%. This is beneficial for increasing the formation of nitrogen oxides.
[0029] like Figure 3 The figure shows a comparison of nitrogen fixation energy consumption between two capillary array micro-discharge nitrogen fixation devices with different inner diameters and a dielectric barrier discharge device without capillary filling, under the same operating conditions. After filling with capillary, the nitrogen fixation energy consumption decreased significantly. The nitrogen fixation energy consumption of the micro-discharge nitrogen fixation device with a 0.1 mm capillary array packed bed is approximately 7.2% of that of the nitrogen fixation device without capillary filling.
[0030] This invention provides a capillary array packed bed micro-discharge nitrogen fixation device, which can generate more micro-discharges under the same voltage, thereby improving nitrogen fixation efficiency. This invention has a simple structure, is easy to operate, has high nitrogen fixation efficiency, can be deployed in a distributed manner, and has broad application prospects.
Claims
1. A capillary array packed bed micro-discharge nitrogen fixation device, characterized in that, The capillary array packed bed micro-discharge nitrogen fixation device includes a rod-shaped electrode, an insulating shell, a capillary array, a grounding electrode, and an insulating plug; The insulating shell is a hollow cylindrical structure, and the rod-shaped electrode is a conductive electrode that axially penetrates the center of the insulating shell and is fixed at both ends by two insulating plugs. The capillary array is arranged in a concentric circle between the outer surface of the rod-shaped electrode and the inner wall of the insulating shell. The side of the insulating plug is provided with through holes, which serve as gas inlets and outlets, respectively, and are connected to an external gas source. Gas flows only through the gas inlet, the gap between the capillaries, and the gas outlet. The grounding electrode covers the outer wall of the insulating shell, wrapping the insulating shell around its circumference.
2. The capillary array packed bed micro-discharge nitrogen fixation device according to claim 1, characterized in that, The rod-shaped electrode is connected to an external power source; the power source is pulse, power frequency AC, or high frequency AC.
3. The capillary array packed bed micro-discharge nitrogen fixation device according to claim 2, characterized in that, in, The pulse power supply is a bipolar pulse power supply with a frequency of 25Hz~200Hz and a peak value of 10kV~25kV; the power frequency AC power supply has an amplitude of 10kV~25kV; the high frequency AC power supply has a frequency of 5kHz~14kHz and an amplitude of 10kV~25kV.
4. The capillary array packed bed micro-discharge nitrogen fixation device according to claim 1, characterized in that, The rod-shaped electrode is made of cylindrical conductive material, such as stainless steel or tungsten; the insulating shell is made of quartz or glass; and the capillary array uses capillary materials with a relative permittivity between 1 and 10.
5. The capillary array packed bed micro-discharge nitrogen fixation device according to claim 1, characterized in that, The rod-shaped electrode has threads or dot-like protrusions on its surface. The thread pitch is adjustable within the range of 0.4 to 4 mm, the diameter of the protrusions is not higher than 1 mm, the height is not higher than 0.5 mm, and the distance between two protrusions is not greater than 1 mm.
6. The capillary array packed bed micro-discharge nitrogen fixation device according to claim 1, characterized in that, The ratio of the inner diameter to the length of the insulating shell is 1:10 to 1:30, and the wall thickness is 0.5 to 2 mm. The inner diameter of the insulating shell is larger than the diameter of the rod-shaped electrode, and the length is shorter than the length of the rod-shaped electrode.
7. The capillary array packed bed micro-discharge nitrogen fixation device according to claim 1, characterized in that, In the capillary array, the inner diameter of a single capillary is 10μm~1000μm, the wall thickness is 100μm, and the length is the same as or slightly shorter than the insulating shell.
8. The capillary array packed bed micro-discharge nitrogen fixation device according to claim 1, characterized in that, The grounding electrode is mesh, strip, or sheet-like, and is made of a conductor material that can withstand currents of 50A or higher. The mesh size of the mesh grounding electrode is not less than 60 meshes, and the thickness of the strip or sheet grounding electrode is not more than 0.5mm. The length of the grounding electrode is shorter than that of the insulating shell. The ratio of the length of the grounding electrode to the length of the capillary array is not less than 1:
5.
9. A capillary array packed bed micro-discharge nitrogen fixation device according to claim 1, characterized in that, The insulating plug can withstand a bipolar pulse voltage with a peak value of 50kV or an AC voltage with an amplitude of 50kV.
10. A capillary array packed bed micro-discharge nitrogen fixation device according to claim 1, characterized in that, The gas flow rate of the external gas source ensures that the residence time of the gas in the capillary array is not less than 0.5 seconds; the external gas source is air or a mixture of nitrogen, oxygen and rare gases, and the volume ratio of nitrogen in the mixture is not less than 5%.