A DBD reactor, system, and method for ammonia synthesis based on a double-bladed propeller flow guide structure.

Abstract

This invention relates to the field of plasma chemical engineering technology and discloses a DBD reactor based on a double-bladed propeller flow guide structure. The reactor includes a central electrode assembly, a dielectric tube, an outer electrode, an insulating cover, and a flow guide gas path structure. The insulating cover is sealed at both ends of the reactor. The central electrode assembly is located inside the center of the dielectric tube, and the outer electrode is sleeved outside the dielectric tube, forming an annular discharge region between them. The flow guide gas path structure is located outside the outer electrode and includes multiple pairs of axially equidistant double-bladed propeller-shaped air inlet channels. These air inlet channels communicate with the annular discharge region, and the air inlet direction is configured tangentially to the cross-section of the dielectric tube, so that the incoming gas forms a continuous annular rotating flow field along the axial length of the annular discharge region to drive catalyst fluidization.

Description

Technical Field

[0001] This invention belongs to the field of plasma chemical technology, and particularly relates to a DBD reactor, system and method for ammonia synthesis based on a double-bladed propeller flow guiding structure. Background Technology

[0002] Traditional industrial ammonia synthesis primarily relies on the Haber-Bosch process, which requires harsh conditions of high temperature (300-500℃) and high pressure (150-200 atm). This process not only consumes enormous amounts of energy but also struggles to achieve efficient coupling with highly volatile renewable energy sources such as wind and solar power. In contrast, non-thermal plasma ammonia synthesis technology based on dielectric barrier discharge (DBD) can activate nitrogen and hydrogen molecules with high-energy electrons at ambient temperature and pressure, completing the synthesis reaction on the catalyst surface. This technology offers advantages such as rapid start-up, compact equipment, and adaptability to intermittent operation, making it a research hotspot in the energy and chemical engineering field in recent years. Current DBD reactors mostly employ a coaxial cylindrical structure, consisting of a central high-voltage electrode, a dielectric tube, and a grounded external electrode. The discharge and reaction occur within the annular gap between the dielectric tube and the electrode.

[0003] Despite the promising prospects of DBD plasma-assisted catalysis technology, it still faces numerous technical bottlenecks in practical applications, particularly in reactor flow field design and mechanical structure. Firstly, regarding catalyst contact, early fixed-bed packing structures are prone to localized overheating and limited diffusion of active species. To address this, gas-solid fluidized bed DBD reactors have emerged, attempting to suspend catalyst particles through gas flow to increase the gas-solid contact area. However, existing fluidized bed DBD reactors mostly employ a single axial bottom inlet method. Since the discharge gap in a DBD reactor is typically extremely narrow (millimeter-level), it is difficult to achieve uniform fluidization of the powdered catalyst within the narrow annular space using only axial airflow. This easily leads to channeling, dead zones, or particle agglomeration, resulting in low catalyst utilization and difficulty in significantly improving reaction conversion. Secondly, in terms of mechanical structure, large-sized or high aspect ratio coaxial DBD reactors require extremely high electrode concentricity. Traditional rigid central electrodes are prone to slight eccentricity or bending after installation or heating, resulting in uneven annular discharge gaps. The electric field strength increases abnormally at smaller gaps, easily inducing filamentary micro-arc discharges and even breaking down the dielectric. This not only disrupts the uniformity of the glow discharge and reduces the selectivity of the chemical reaction, but also severely shortens the reactor's lifespan. Furthermore, the direct emission of unreacted feed gas also leads to low overall system energy efficiency.

[0004] Therefore, in the field of plasma ammonia synthesis, existing reactor structures still have significant shortcomings in terms of fluid dynamics and mechanical stability. How to achieve a uniform, stable, and long-term fluidization state of catalyst particles within a narrow annular discharge space without significantly increasing the gas flow rate, thus eliminating dead zones; how to ensure high consistency of the discharge gap in the axial and radial directions by improving the electrode support structure to prevent energy waste and equipment damage caused by uneven local discharge; and how to construct an efficient product collection and feedstock recycling system to improve the overall system energy efficiency are the key technical problems that urgently need to be solved in the process of this technology moving from the laboratory to industrial application. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a DBD reactor, system, and method for ammonia synthesis based on a double-bladed propeller flow guide structure.

[0006] Firstly, a DBD reactor based on a double-bladed propeller flow guiding structure adopts the following technical solution: A DBD reactor based on a dual-blade propeller flow guide structure includes: a central electrode assembly, a dielectric tube, an outer electrode, an insulating cover, and a flow guide gas path structure. The insulating cover includes a first insulating cover and a second insulating cover, which are respectively sealed and installed at both ends of the axial direction of the outer electrode; the central electrode assembly is disposed at the inner center of the dielectric tube, and the two ends of the central electrode assembly are respectively fixedly connected to the first insulating cover and the second insulating cover; the outer electrode is sleeved on the outside of the dielectric tube, and an annular discharge region is formed between the outer wall of the dielectric tube and the inner wall of the outer electrode. The airflow path structure is located outside the outer electrode and includes multiple pairs of equidistant double-bladed propeller-shaped air intake channels along the axial direction. The air intake channels are connected to the annular discharge region, and the air intake direction of the air intake channels is configured to be tangential to the cross-section of the dielectric tube, so that the incoming gas forms a continuous annular rotating flow field along the axial length of the annular discharge region.

[0007] Furthermore, each pair of double-bladed propeller-shaped air intake channels in the airflow guiding structure includes a centrally symmetrical first air intake and a second air intake. The first air inlet is configured to tangentially introduce the raw material gas from a first direction to form a first semi-circular flow line flowing along the outer wall of the dielectric tube in the lower part of the annular discharge region; the second air inlet is configured to tangentially introduce the raw material gas from a second direction to form a second semi-circular flow line flowing along the outer wall of the dielectric tube in the upper part of the annular discharge region. The first semi-circular flow line and the second semi-circular flow line converge at the periphery of the medium tube to form the annular rotating flow field.

[0008] Furthermore, the outer electrode is provided with a total of 6 pairs of equidistant double-bladed propeller-shaped air intake channels along the axial direction; all the air intake channels have the same tangential deflection angle, which is used to maintain a stable spiral airflow throughout the entire annular discharge area.

[0009] Furthermore, the central electrode assembly includes a metal rod, a wire brush, and an inner electrode; The metal rod is located on the central axis of the dielectric tube, with one end fixed to the first insulating cover and the other end fixed to the second insulating cover; the wire brush is radially mounted on the outer circumferential surface of the metal rod, and the inner electrode covers the outside of the wire brush; The bristles of the wire brush are in close contact with the inner surface of the inner electrode, and the outer surface of the inner electrode is always in close contact with the inner wall of the dielectric tube, so as to make electrical connection between the metal rod and the inner electrode.

[0010] Furthermore, the first insulating cover is located on one side of the DBD reactor and is used to fix one end of the metal rod; the second insulating cover is located on the other side of the DBD reactor and is used to fix the other end of the metal rod; the DBD reactor also includes a gas outlet, which is installed outside the second insulating cover and is used to discharge the gaseous products after the reaction.

[0011] Furthermore, the outer electrode is grounded, and the central electrode assembly is connected to a high-voltage power supply; the annular discharge region is filled with a powdered catalyst; the powdered catalyst undergoes fluidized motion around the outer wall of the medium tube under the drive of the annular rotating flow field.

[0012] Secondly, a DBD plasma ammonia synthesis collection system based on a dual-blade propeller guide structure adopts the following technical solution: A DBD plasma ammonia synthesis collection system based on a dual-bladed propeller guide structure includes: The DBD reactor based on the double-bladed propeller flow guide structure as described above; And connected in sequence through pipelines are a gas temperature control module, a multi-stage condensation and separation module, an ammonia selective separation module, and a raw material gas recycling module; The input terminal of the gas temperature control module is connected to the gas outlet of the DBD reactor and is used to perform variable temperature heat exchange on the reaction products. The multi-stage condensation and separation module is used to condense the cooled gas in stages to collect liquid ammonia; The ammonia selective separation module is used to adsorb and separate residual ammonia in the tail gas. The output of the raw material gas recycling module is connected to the air inlet channel of the DBD reactor, and the processed raw material gas is sent back to the reactor.

[0013] Furthermore, the multi-stage condensation separation module includes a primary cryogenic condensation unit and a secondary constant-temperature condensation unit connected in series; The input end of the first-stage cryogenic condensation unit is connected to the output end of the gas temperature control module, and is used to rapidly condense high-concentration ammonia gas. The input end of the secondary constant temperature condensation unit is connected to the output end of the primary cryogenic condensation unit, and is used to release residual ammonia in the tail gas. The ammonia selective separation module is equipped with an ammonia-repellent microporous membrane adsorption material, and its input end is connected to the output end of the secondary constant temperature condensation unit.

[0014] Thirdly, a method for plasma ammonia synthesis using the above-mentioned reactor employs the following technical solution: A method for plasma ammonia synthesis using the above-mentioned reactor includes the following steps: Nitrogen and hydrogen are mixed as raw materials and introduced into the annular discharge region tangentially along the axial direction through the multiple pairs of double-bladed propeller-shaped air inlet channels. An annular rotating flow field is formed between the outer wall of the dielectric tube and the outer electrode, which drives the powdered catalyst filled therein to fluidize. An alternating high voltage is applied between the central electrode assembly and the external electrode to generate a dielectric barrier discharge plasma, which allows the raw material gas to be synthesized into ammonia under the action of a catalyst. The mixed gas after the reaction is taken out and sequentially subjected to variable temperature heat exchange, cryogenic condensation and isothermal condensation to separate liquid ammonia in stages. The uncondensed tail gas is selectively adsorbed and separated by ammonia, and the remaining unreacted raw material gas is adjusted in composition and proportion and then returned to the reactor.

[0015] Furthermore, the volume ratio of nitrogen to hydrogen in the raw material gas is 1:1, and the total gas flow rate is controlled at 3-6 L / min; The output voltage range of the AC high voltage is 0-10 kV, the frequency is 5-6 kHz, the breakdown voltage is controlled at 7-10 kV, and the gas temperature is maintained at 600-700 K during the discharge process.

[0016] The beneficial effects of this invention are: This invention provides a DBD reactor based on a double-bladed propeller flow guide structure. By setting multiple pairs of axially equidistant double-bladed propeller-shaped tangential air inlet channels outside the outer electrode, the flow field mode of the traditional single axial air inlet is changed, enabling the incoming feed gas to acquire significant tangential momentum and forming a high-intensity, continuous spiral rotating flow field within the narrow annular discharge gap. The centrifugal force and shear force generated by this rotating flow field can effectively overcome the gravity and agglomeration force of the powdered catalyst, driving the catalyst particles to adhere tightly to the outer wall of the dielectric tube and perform circumferential spiral upward motion. This eliminates dead zones and channeling phenomena, significantly increases the contact path and residence time between the reactant gas and the catalyst surface, and significantly improves the synergistic reaction efficiency of gas-solid-plasma. Meanwhile, the central electrode assembly adopts a support structure of metal rod and wire brush. The elastic radial support force of the wire brush bristles forces the inner electrode layer to always be tightly attached to the inner wall of the dielectric tube. This flexible adaptive support not only achieves good electrical contact, but more importantly, it achieves automatic centering of the inner electrode and the dielectric tube, ensuring the high geometric uniformity of the external annular discharge gap in both circumference and axial direction. This effectively avoids the risk of local electric field distortion and micro-arc discharge caused by electrode eccentricity, ensuring the uniformity and stability of glow discharge, extending equipment life and improving energy utilization. Attached Figure Description

[0017] Figure 1 This is a three-dimensional structural diagram of the DBD reactor in an embodiment of the present invention; Figure 2 This is a schematic diagram of the DBD reactor from the main viewpoint in an embodiment of the present invention; Figure 3 for Figure 2 Cross-sectional view from the perspective of AA (American Academy of Sciences); Figure 4 for Figure 2 A cross-sectional view from the perspective of a mid-BB (Black-Body) plane; Figure 5 for Figure 2 A cross-sectional view from a medium CC perspective.

[0018] Reference numerals: 100, DBD reactor; 110, central electrode assembly; 111, metal rod; 112, wire brush; 113, inner electrode; 120, dielectric tube; 130, outer electrode; 140, insulating cover; 141, first insulating cover; 142, second insulating cover; 150, airflow path structure; 151, air inlet channel; 1511, first air inlet; 1512, second air inlet; 160, annular discharge region; 170, air outlet. Detailed Implementation

[0019] The following detailed description, in conjunction with embodiments, provides an explanation of the DBD reactor, system, and ammonia synthesis method based on a dual-blade propeller flow guide structure according to the present invention. For the sake of simplicity, this document cannot exhaustively list all alternative technical features and embodiments included in the present invention. Therefore, those skilled in the art should understand that any technical feature and embodiment within this embodiment does not limit the scope of protection of the present invention. The scope of protection includes all alternative technical features and embodiments adopted by those skilled in the art without inventive effort. Specifically, any embodiment obtained by replacing any technical feature in the present invention or by combining any two or more technical features provided by the present invention should be within the scope of protection of the present invention.

[0020] The following is in conjunction with the instruction manual. Figures 1 to 5 This paper provides a detailed description of the DBD reactor, collection system, and method based on a double-bladed propeller flow guide structure provided by the present invention.

[0021] See Figures 1 to 5 This embodiment provides a DBD (Dielectric Barrier Discharge) reactor 100 based on a dual-blade propeller flow-guiding structure. The overall structure of the DBD reactor 100 is based on a coaxial cylindrical geometry. Through the deep integration of specific fluid dynamics and mechanical support structures, it achieves control of the gas-solid two-phase flow and maintenance of the discharge gap within a millimeter-level micro-gap. The main components of the DBD reactor 100 include a central electrode assembly 110, a dielectric tube 120, an outer electrode 130, an insulating cover 140, and a flow-guiding gas path structure 150. The dielectric tube 120 is made of a material with high dielectric constant, high-voltage breakdown resistance, and chemical stability, such as quartz glass or alumina ceramic. Its shape is a hollow cylindrical tube, serving as a barrier to prevent the discharge current from converting into arc discharge. The outer electrode 130 is made of a metallic material with excellent conductivity, such as stainless steel mesh, copper foil, or a silver plating layer. It is sleeved on the outer circumferential surface of the dielectric tube 120 and is configured as a grounding terminal. In terms of spatial topology, the outer electrode 130 is sleeved outside the dielectric tube 120. The outer wall of the dielectric tube 120 and the inner wall of the outer electrode 130 are not completely fitted together, but rather a ring-shaped space with a specific radial width is reserved or defined. This space is the ring-shaped discharge region 160. The ring-shaped discharge region 160 is the core site for non-equilibrium plasma discharge and gas-solid multiphase catalytic reactions. Under actual working conditions, this region is filled with powdered catalysts, such as supported metal catalyst particles, to assist the ammonia synthesis reaction.

[0022] The insulating cover 140 includes a first insulating cover 141 and a second insulating cover 142, which are respectively sealed and installed at both ends of the cylindrical structure formed by the outer electrode 130 and the dielectric tube 120. The insulating cover 140 is made of highly insulating and corrosion-resistant materials such as polytetrafluoroethylene or special ceramics. Its function is not only to seal the reaction chamber to maintain the internal gas pressure environment, but also to provide an axial positioning reference and mechanical support for the internal components. The central electrode assembly 110 is disposed in the central cavity inside the dielectric tube 120 and extends strictly along the central axis of the dielectric tube 120. The axial ends of the central electrode assembly 110 pass through and are fixedly connected to the central holes of the first insulating cover 141 and the second insulating cover 142, thereby realizing the suspension fixation of the central electrode assembly 110 relative to the dielectric tube 120.

[0023] The gas flow path structure 150 is located outside the outer electrode 130. The gas flow path structure 150 is not a traditional single-point injection or simple axial distribution pipe, but rather includes multiple pairs of axially equidistant, double-bladed propeller-shaped air intake channels 151. Each air intake channel 151 is fluidly connected to the annular discharge region 160, allowing external raw material gas to enter the annular discharge region 160. Specifically, the air intake direction of the air intake channel 151 is configured to be tangential to the cross-section of the dielectric tube 120. Here, "tangential arrangement" means that the direction vector of the gas flow injection does not pass through the center of the dielectric tube 120, but is tangential to a concentric circle on the cross-section of the dielectric tube 120, or forms a 90-degree angle with the normal direction of the outer wall of the dielectric tube 120. The physical significance of this geometric configuration is that when the high-pressure nitrogen and hydrogen mixture is injected at high speed into the annular discharge region 160 through the air intake channel 151, the gas molecules instantly acquire a large tangential momentum component. Since the annular discharge region 160 is a closed annular channel, the gas with tangential velocity cannot diffuse radially in a straight line and is forced to move in a circular motion along the outer wall of the medium tube 120. Furthermore, because the gas path structure is distributed at multiple points along the axial direction, and the gas also has an axial pressure gradient, the actual trajectory of the airflow is synthesized into a spiral. This continuous annular rotating flow field formed along the axial length of the annular discharge region 160, utilizing the centrifugal force and shear force generated by the fluid, effectively overcomes the van der Waals forces and gravity between the powdered catalyst particles, driving the catalyst particles to adhere tightly to the outer wall of the medium tube 120 and undergo a circumferential spiral upward motion under the entrainment of the airflow, thereby achieving fluidization of the catalyst particles. This fluidization state differs from the up-and-down boiling of traditional fluidized beds; it is a thin-layer fluidization with wall-attached rotation, greatly increasing the contact path length and contact time between the gas and the catalyst surface.

[0024] like Figure 4 (Section BB) and Figure 5As shown in cross-section CC, each pair of double-bladed propeller-shaped air intake channels 151 spatially includes a centrally symmetrical first air intake 1511 (i.e., the upper left air intake) and a second air intake 1512 (i.e., the lower right air intake). Specifically, the first air intake 1511 is configured to introduce the raw material gas from the upper left tangential position. After the airflow enters the annular discharge region 160, it slides downward along the outer wall of the dielectric tube 120 under the action of inertia, thereby forming a first semi-circular flow line flowing along the outer wall of the dielectric tube 120 in the lower part of the annular discharge region 160. Correspondingly, the second air intake 1512 is configured to introduce the raw material gas from the lower right tangential position. After the airflow enters, it slides upward along the outer wall of the dielectric tube 120, forming a second semi-circular flow line flowing along the outer wall of the dielectric tube 120 in the upper part of the annular discharge region 160. The first and second semi-circular flow lines meet end-to-end at the periphery of the dielectric tube 120 (i.e., within the annular discharge region 160), superimposing their momentum and ultimately merging to form a complete, high-intensity annular rotating flow field. This double-sided symmetrical tangential air intake design, compared to single-sided tangential air intake, can significantly reduce turbulent dissipation in the initial stage of flow field establishment, making the rotating airflow more stable and symmetrical. It avoids the problem of catalyst particles accumulating on the opposite side that may occur with single-sided air intake, ensuring the circumferential uniformity of the catalyst layer thickness.

[0025] In this embodiment, to ensure the uniformity of the flow field along the entire length of the reactor, six pairs of equidistant double-bladed propeller-shaped air inlet channels 151 are axially arranged outside the outer electrode 130. The axial spacing of these six pairs of air inlet channels 151 is calculated to ensure that the spiral flow fields generated by adjacent air inlets can be smoothly connected, avoiding axial flow dead zones. More importantly, the tangential deflection angle of all air inlet channels 151 remains the same, which means that all incoming gas contributes to the same rotation direction (e.g., all clockwise or all counterclockwise), thereby maintaining a stable spiral airflow throughout the entire annular discharge region 160. If the deflection angles are inconsistent, it will lead to airflow collision and momentum cancellation, disrupting the fluidization state.

[0026] Based on the principle of momentum conservation in fluid mechanics, the flow field generated by the above structure can be quantitatively described. Assuming the tangential momentum flux obtained by the feed gas introduced from one of the upper left inlets (such as the first inlet 1511) under the guiding effect is M, it can be expressed as: ; Where ρ is the density of the intake gas, U j A is the velocity of the raw material gas ejected from the inlet nozzle. j Let be the cross-sectional area of ​​the inlet nozzle, and α be the tangential angle (i.e., the angle between the inlet direction and the radial direction) of the jet after deflection by the guide structure. This tangential momentum is distributed to the semi-circular region surrounding the medium pipe, and its average circumferential velocity... The momentum conservation relationship is satisfied: ; Among them, A half Let be the effective cross-sectional area of ​​the semi-circular region surrounding the medium pipe. From this, the order of magnitude of the average circumferential velocity caused by a single-channel intake airflow is approximately: ; From the above equation, it can be seen that as long as the jet has a non-zero tangential component, that is: ; This will inevitably result in a non-zero circumferential velocity around the periphery of the medium pipe 120. Furthermore, the strength of this circumferential velocity is related to the nozzle size A. j Jet velocity U j And it is proportional to the deflection angle α, and to the area A of the semi-circular region. half Inversely proportional. This formula demonstrates that the invention utilizes structural design parameters (A... j (α) Feasibility of controlling the flow field intensity. This demonstrates that the double-sided semicircular streamlines can form a stable annular airflow structure around the medium tube.

[0027] like Figure 3 (Section AA) and Figure 4 As shown in section BB, the central electrode assembly 110 is not a simple metal rod, but a composite structure consisting of a metal rod 111, a wire brush 112, and an inner electrode 113. The metal rod 111 is located on the geometric center axis of the dielectric tube 120 and is made of a highly conductive and mechanically strong material (such as stainless steel or copper). One end is fixed to the first insulating cover 141, and the other end is fixed to the second insulating cover 142, serving as the support for the entire assembly and responsible for introducing high-voltage power. The wire brush 112 is radially mounted on the outer circumferential surface of the metal rod 111 and is composed of a large number of fine conductive spring steel wires arranged radially. The inner electrode 113 is a thin-walled metal tube or flexible metal foil layer covering the wire brush 112.

[0028] The bristle length of the wire brush 112 is designed to be slightly greater than the theoretical distance between the surface of the metal rod 111 and the inner surface of the inner electrode 113, so that in the assembled state, the bristles of the wire brush 112 are in a pre-tightened state under pressure and bending. The bristle tips are in close contact with the inner surface of the inner electrode 113, and the radial elastic support force generated by the deformation of the wire brush 112 itself pushes the inner electrode 113 outward. This uniformly distributed radial tension ensures that the outer surface of the inner electrode 113 is always in close contact with the inner wall of the dielectric tube 120. This design achieves three functions: First, it establishes a reliable multi-point electrical connection between the metal rod 111 and the inner electrode 113, ensuring lossless transmission of high-voltage electrical energy to the discharge interface. Second, by utilizing the flexible adaptive capability of the wire brush, it eliminates the air gap between the inner electrode 113 and the inner wall of the dielectric tube 120, preventing ineffective discharge or breakdown inside the dielectric tube. Third, and most importantly, the rigid support provided by the wire brush acts as a mechanical centering mechanism. Even with minor installation errors or thermal bending of the metal rod 111, the wire brush ensures that the inner electrode 113 remains tightly attached to the inner wall of the dielectric tube 120, thereby guaranteeing a consistent circumferential spacing between the annular discharge region 160 between the dielectric tube 120 and the outer electrode 130. This high degree of geometric uniformity is a prerequisite for generating uniform glow discharge and avoiding localized micro-arc discharges, significantly improving the reactor's operational stability and energy utilization rate.

[0029] In terms of circuit connections, the outer electrode 130 is configured to be grounded, and the central electrode assembly 110 (metal rod 111) is connected to the high-voltage output terminal of the AC high-voltage power supply. When the high-voltage power supply is started, an alternating strong electric field is formed between the inner electrode 113 (high-voltage terminal) and the outer electrode 130 (grounded terminal). This electric field penetrates the dielectric tube 120 and generates dielectric barrier discharge (DBD) within the annular discharge region 160. A large number of high-energy electrons are generated within the discharge region. These electrons collide with nitrogen and hydrogen molecules, causing them to dissociate, excite, or ionize, generating reactive nitrogen species (such as N, N2). * ) and active hydrogen species (H, H * Meanwhile, the annular discharge region 160 is filled with powdered catalyst. Driven by the aforementioned rotating gas flow, these catalyst particles float and rotate around the outer wall of the dielectric tube 120, remaining in an active fluidized state. Active species in the plasma diffuse to the fluidized catalyst surface, undergoing adsorption and combination reactions at the catalyst's active sites to generate ammonia (NH3). The fluidized catalyst particles not only provide a large gas-solid contact area but also continuously renew the surface gas film through movement, enhancing the mass transfer process and contributing to the uniform dissipation of discharge heat, preventing localized overheating that could lead to catalyst deactivation.

[0030] To facilitate the removal of the reaction products, the DBD reactor 100 also includes an outlet 170. For example... Figure 2 and Figure 3As shown, the outlet 170 is installed at the outer center or eccentric position of the second insulating cover 142. The outlet 170 is directly connected to the annular discharge region 160 through a channel on the second insulating cover 142. The mixed gas after the reaction (containing the generated ammonia and unreacted nitrogen and hydrogen) flows along a spiral path to the end of the reactor under the pressure of the gas flow, and finally converges and is discharged from the reactor through the outlet 170.

[0031] This embodiment also provides a DBD plasma ammonia synthesis collection system based on the aforementioned DBD reactor 100. The system mainly consists of the DBD reactor 100, a gas temperature control module, a multi-stage condensation and separation module, an ammonia selective separation module, and a raw material gas recycling module, which are sequentially connected by pipelines.

[0032] The input of the gas temperature control module is connected to the outlet 170 of the DBD reactor 100. Since DBD discharge generates heat (although it is non-thermal plasma, the gas temperature can still reach 300-400℃ at high power densities), directly introducing it into the condensation unit would lead to excessive energy consumption and could easily damage the equipment. The gas temperature control module employs a variable-temperature heat exchanger structure. By adjusting the flow rate and temperature gradient of the cooling medium, it controllably cools the high-temperature mixed gas generated in the reaction, reducing its temperature to a predetermined range suitable for subsequent condensation (e.g., room temperature or around 0℃), while simultaneously recovering some of the heat energy.

[0033] A multi-stage condensation separation module is used to perform staged condensation of cooled gas to achieve efficient ammonia collection. This module specifically includes a primary cryogenic condensation unit and a secondary isothermal condensation unit connected in series. The input of the primary cryogenic condensation unit is connected to the output of the gas temperature control module. This unit uses liquid nitrogen or a compressor for refrigeration, providing extremely low condensation temperatures (e.g., -30°C to -70°C). Its purpose is to utilize the fact that ammonia's boiling point (-33.34°C) is much higher than that of nitrogen and hydrogen, rapidly condensing the high concentration of ammonia in the mixed gas into liquid ammonia, which is then collected from the bottom. The input of the secondary isothermal condensation unit is connected to the gas output of the primary cryogenic condensation unit. After primary condensation, a small amount of ammonia saturated vapor may still remain in the gas flow. The secondary isothermal condensation unit maintains a constant low temperature (e.g., -40°C), further precipitating the residual ammonia in the exhaust gas by extending the residence time and increasing the heat exchange area, minimizing ammonia loss.

[0034] The ammonia selective separation module is used to treat tail gas that still contains trace amounts of ammonia after condensation. Its input is connected to the output of the secondary isothermal condensation unit. This module is filled with materials that have a high selective adsorption capacity for ammonia, such as ammonia-repellent microporous membrane adsorbents, metal halide adsorbents, or modified zeolites. These materials can capture trace amounts of ammonia in the gas stream at the ppm level, not only improving the overall ammonia recovery rate but, more importantly, preventing ammonia from entering subsequent circulation loops and poisoning the catalyst or affecting the gas ratio. After adsorption saturation, the material can be regenerated through temperature-swing or pressure-swing desorption, and the recovered ammonia is incorporated into the product stream.

[0035] The feed gas recycling module is crucial for achieving closed-loop system operation. It includes a tail gas component adjustment unit and a nitrogen-hydrogen ratio adjustment unit. The tail gas component adjustment unit's input is connected to the output of the ammonia selective separation module, separating unreacted nitrogen and hydrogen from the tail gas and removing inert components (such as argon) or impurities that may be introduced during the reaction process, preventing their accumulation in the cycle. The nitrogen-hydrogen ratio adjustment unit is connected after the tail gas component adjustment unit and is equipped with replenishment lines for fresh nitrogen and hydrogen, as well as a mass flow controller. This unit automatically replenishes consumed nitrogen and hydrogen based on the detected circulating gas composition, readjusting the nitrogen-hydrogen molar ratio of the mixed gas to the optimal reaction ratio (e.g., 1:1 or 1:3). The output of the feed gas recycling module is ultimately connected to the inlet channel 151 (i.e., the first inlet 1511 and the second inlet 1512) of the DBD reactor 100, returning the treated regenerated feed gas to the reactor to form a closed-loop cycle.

[0036] Based on the above apparatus and system, this embodiment also provides a method for plasma ammonia synthesis, which includes the following steps performed sequentially: High-purity nitrogen (N2) and high-purity hydrogen (H2) are mixed as feed gas at a predetermined volume ratio (e.g., 1:1 to 1:3) using a mass flow controller. The feed gas is then introduced into a guide gas path structure 150 outside the external electrode 130. The gas is distributed into six pairs of axially equidistant, double-bladed propeller-type inlet channels 151. In each pair of channels, gas is injected tangentially into the annular discharge region 160 from the first inlet 1511 (upper left) and the second inlet 1512 (lower right), respectively. Due to the geometric constraint of the tangential inlet, the gas acquires significant tangential momentum. The airflow from the upper left flows downward along the outer wall of the dielectric tube 120, forming a semi-annular flow, while the airflow from the lower right flows upward along the outer wall, forming another semi-annular flow. The two flows merge to form a high-intensity annular rotating flow field between the outer wall of the dielectric tube 120 and the external electrode 130. The rotational speed and turbulence intensity of the flow field are sufficient to drive the powdered catalyst (such as M / Al2O3, where M is an active metal such as Co or Ru) filled in the annular discharge region 160 to break free from the constraints of gravity and undergo a spiral upward fluidization motion along the outer wall of the medium tube, forming a uniform fluidized bed.

[0037] A high-voltage AC power supply is activated, applying high voltage between the central electrode assembly 110 (high-voltage end) and the external electrode 130 (grounding end). Specific electrical parameters are set as follows: output voltage range 0-10 kV, frequency range 5-6 kHz. Within this parameter range, the voltage is adjusted to the breakdown voltage (typically between 7-10 kV), causing the gas medium within the annular discharge region 160 to break down, generating numerous fine filamentary discharges or uniform glow discharges, forming a non-equilibrium plasma. During the discharge process, the gas temperature in the discharge region is controlled by a cooling system to maintain it between 600-700 K, balancing plasma activity and catalyst thermal stability. Under the high-energy electron bombardment of the plasma, N2 and H2 molecules dissociate and become excited, generating highly active nitrogen atoms, hydrogen atoms, and excited-state molecules. These active species diffuse to the catalyst surface undergoing helical fluidization, overcoming the energy barrier to synthesize ammonia under the synergistic effect of the catalyst. The strong disturbance brought by the rotating flow field greatly promotes the mass transfer of active species to the catalyst surface and promptly removes the product ammonia, thereby significantly improving the synthesis efficiency.

[0038] The reacted gas mixture (containing the product ammonia and unreacted feed gas) is discharged from the reactor through outlet 170 under gas pressure. The high-temperature gas first undergoes heat exchange and cooling through a gas temperature control module. Subsequently, the gas enters a primary cryogenic condensation unit, where most of the ammonia undergoes a phase change and liquefies at extremely low temperatures, and is collected. The unliquefied gas continues to enter a secondary isothermal condensation unit for further cooling and separation of residual ammonia. This staged condensation process ensures a high ammonia recovery rate.

[0039] The exhaust gas from the condensation module enters the ammonia selective separation module, where trace amounts of residual ammonia are adsorbed and retained using materials such as ammonia-repellent microporous membranes. The deeply purified exhaust gas mainly consists of nitrogen and hydrogen, which enter the feed gas recycling module. Based on the exhaust gas composition analysis, the system replenishes appropriate amounts of fresh nitrogen and hydrogen, adjusting the gas pressure, flow rate, and ratio (e.g., maintaining an N2:H2 volume ratio of 1:1 and controlling the total flow rate at 3-6 L / min) to the initial set values, and then returns it to the inlet of the DBD reactor to participate in the next round of synthesis reaction.

[0040] In summary, this invention, through its unique double-bladed propeller flow guiding structure and wire brush electrode support design, successfully solves the problems of catalyst fluidization and discharge stability in traditional DBD reactors. Combined with an integrated collection and circulation system, it achieves a highly efficient, stable, and low-energy-consumption plasma ammonia synthesis process.

[0041] For those skilled in the art, other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations, but obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this invention.

Claims

1. A DBD reactor based on a double-bladed propeller flow guiding structure, characterized in that, include: The central electrode assembly, dielectric tube, external electrode, insulating cover, and airflow path structure; The insulating cover includes a first insulating cover and a second insulating cover, which are respectively sealed and installed at both ends of the axial direction of the outer electrode; the central electrode assembly is disposed at the inner center of the dielectric tube, and the two ends of the central electrode assembly are respectively fixedly connected to the first insulating cover and the second insulating cover; the outer electrode is sleeved on the outside of the dielectric tube, and an annular discharge region is formed between the outer wall of the dielectric tube and the inner wall of the outer electrode. The airflow path structure is located outside the outer electrode and includes multiple pairs of equidistant double-bladed propeller-shaped air intake channels along the axial direction. The air intake channels are connected to the annular discharge region, and the air intake direction of the air intake channels is configured to be tangential to the cross-section of the dielectric tube, so that the incoming gas forms a continuous annular rotating flow field along the axial length of the annular discharge region.

2. The DBD reactor based on a double-bladed propeller flow guiding structure according to claim 1, characterized in that, Each pair of double-bladed propeller-shaped air intake channels in the airflow path structure includes a centrally symmetrical first air intake and a second air intake. The first air inlet is configured to tangentially introduce the raw material gas from a first direction to form a first semi-circular flow line flowing along the outer wall of the dielectric tube in the lower part of the annular discharge region; the second air inlet is configured to tangentially introduce the raw material gas from a second direction to form a second semi-circular flow line flowing along the outer wall of the dielectric tube in the upper part of the annular discharge region. The first semi-circular flow line and the second semi-circular flow line converge at the periphery of the medium tube to form the annular rotating flow field.

3. The DBD reactor based on a double-bladed propeller flow guiding structure according to claim 1, characterized in that, The outer electrode has six pairs of equidistant double-bladed propeller-shaped air intake channels arranged along the axial direction; all the air intake channels have the same tangential deflection angle, which is used to maintain a stable spiral airflow throughout the entire annular discharge area.

4. The DBD reactor based on a double-bladed propeller flow guide structure according to claim 1, characterized in that, The central electrode assembly includes a metal rod, a wire brush, and an inner electrode; The metal rod is located on the central axis of the dielectric tube, with one end fixed to the first insulating cover and the other end fixed to the second insulating cover; the wire brush is radially mounted on the outer circumferential surface of the metal rod, and the inner electrode covers the outside of the wire brush; The bristles of the wire brush are in close contact with the inner surface of the inner electrode, and the outer surface of the inner electrode is always in close contact with the inner wall of the dielectric tube, so as to make electrical connection between the metal rod and the inner electrode.

5. The DBD reactor based on a double-bladed propeller flow guiding structure according to claim 4, characterized in that, The first insulating cover is located on one side of the DBD reactor and is used to fix one end of the metal rod; the second insulating cover is located on the other side of the DBD reactor and is used to fix the other end of the metal rod; the DBD reactor also includes a gas outlet, which is installed outside the second insulating cover and is used to discharge the gaseous products after the reaction.

6. The DBD reactor based on a double-bladed propeller flow guiding structure according to claim 1, characterized in that, The outer electrode is grounded, and the central electrode assembly is connected to a high-voltage power supply; the annular discharge region is filled with powdered catalyst; the powdered catalyst undergoes fluidized motion around the outer wall of the medium tube under the drive of the annular rotating flow field.

7. A DBD plasma ammonia synthesis collection system based on a double-bladed propeller guide structure, characterized in that, include: DBD reactor based on a dual-blade propeller flow guide structure as described in any one of claims 1 to 6; And connected in sequence through pipelines are a gas temperature control module, a multi-stage condensation and separation module, an ammonia selective separation module, and a raw material gas recycling module; The input terminal of the gas temperature control module is connected to the gas outlet of the DBD reactor and is used to perform variable temperature heat exchange on the reaction products. The multi-stage condensation and separation module is used to condense the cooled gas in stages to collect liquid ammonia; The ammonia selective separation module is used to adsorb and separate residual ammonia in the tail gas. The output of the raw material gas recycling module is connected to the air inlet channel of the DBD reactor, and the processed raw material gas is sent back to the reactor.

8. The DBD plasma ammonia synthesis collection system based on a double-bladed propeller guide structure according to claim 7, characterized in that, The multi-stage condensation separation module includes a primary cryogenic condensation unit and a secondary constant-temperature condensation unit connected in series. The input end of the first-stage cryogenic condensation unit is connected to the output end of the gas temperature control module, and is used to rapidly condense high-concentration ammonia gas. The input end of the secondary constant temperature condensation unit is connected to the output end of the primary cryogenic condensation unit, and is used to release residual ammonia in the tail gas. The ammonia selective separation module is equipped with an ammonia-repellent microporous membrane adsorption material, and its input end is connected to the output end of the secondary constant temperature condensation unit.

9. A method for plasma ammonia synthesis using the reactor as described in claim 1, characterized in that, Includes the following steps: Nitrogen and hydrogen are mixed as raw materials and introduced into the annular discharge region tangentially along the axial direction through the multiple pairs of double-bladed propeller-shaped air inlet channels. An annular rotating flow field is formed between the outer wall of the dielectric tube and the outer electrode, which drives the powdered catalyst filled therein to fluidize. An alternating high voltage is applied between the central electrode assembly and the external electrode to generate a dielectric barrier discharge plasma, which allows the raw material gas to be synthesized into ammonia under the action of a catalyst. The mixed gas after the reaction is taken out and sequentially subjected to variable temperature heat exchange, cryogenic condensation and isothermal condensation to separate liquid ammonia in stages. The uncondensed tail gas is selectively adsorbed and separated by ammonia, and the remaining unreacted raw material gas is adjusted in composition and proportion and then returned to the reactor.

10. The method according to claim 9, characterized in that, The volume ratio of nitrogen to hydrogen in the raw material gas is 1:1, and the total gas flow rate is controlled at 3-6 L / min. The output voltage range of the AC high voltage is 0-10 kV, the frequency is 5-6 kHz, the breakdown voltage is controlled at 7-10 kV, and the gas temperature is maintained at 600-700 K during the discharge process.

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