Integrated insulation flow channel device with filtering function, preparation method and application

Abstract

The application belongs to the field of magnetic confinement nuclear fusion reactor engineering technology, and discloses an integrated insulation flow channel device with filtering function, a preparation method and application. The device comprises a porous ceramic filter core, a metalized brazing sealing assembly and a metal shell which are sequentially arranged from inside to outside in the radial direction. The porous ceramic filter core comprises a porous filter core main body and an annular dense edge arranged on the outer periphery of the porous filter core main body. The porous filter core main body is a three-dimensional interconnected pore structure. The porous filter core main body and the annular dense edge are integrally formed. The metalized brazing sealing assembly is sealingly connected between the annular dense edge and the metal shell. The application can maintain the basic MHD suppression effect consistent with the traditional dense flow channel insert, and at the same time, achieve a filtering efficiency of ≥99% for solid impurities of 10 microns or more in the liquid metal loop. The application has the significant advantages of simple structure, high reliability, low cost and long service life.

Description

Technical Field

[0001] This invention belongs to the field of magnetic confinement nuclear fusion reactor engineering technology, and particularly relates to an integrated insulating flow channel device with filtration function, its preparation method and application. Background Technology

[0002] The liquid lithium-lead blanket of a magnetic confinement fusion reactor operates in an extremely strong magnetic field environment (the central magnetic field reaches 14T). When liquid Pb-17Li is used as a coolant and tritium breeder and circulates at high speed in the loop, it faces the following two unavoidable and interrelated core technical challenges, which seriously restrict the reliability and economy of the blanket system.

[0003] I. Solid impurities cause system performance degradation.

[0004] At the operating temperature of the liquid lithium-lead loop in a fusion reactor (≥500℃), lithium and lead selectively dissolve with structural materials such as 316H stainless steel and RAFM steel (low-activation ferrite / martensitic steel), precipitating intermetallic compound particles containing Fe, Cr, and Ni in temperature or concentration gradient regions. The particle size is mainly distributed in the range of 1~20μm. These solid particles, i.e., solid impurities, can cause multiple hazards: (1) depositing on the heat exchange surface of the heat exchanger, resulting in a decrease in heat exchange efficiency of 10%~30%; (2) clogging the small channels of valves, flow meters, and safety relief devices, increasing system resistance; (3) wearing out the impeller and bearings of the circulating pump, shortening the service life of key equipment; (4) entering the tritium extraction system, covering the surface of the extraction element, and reducing the tritium extraction efficiency.

[0005] Existing technologies typically use metal wire mesh filters or sintered metal filters to filter the above-mentioned solid impurities, but they have the following inherent defects: (1) Severe electrochemical corrosion: Different metal parts form galvanic cells in high-temperature lithium lead, and the corrosion rate of 316H stainless steel filters can reach 1~2μm / year, and they usually fail after 2~3 years of operation; (2) Contradiction between filtration accuracy and resistance: In order to intercept impurities larger than 10μm, pore size ≤10μm is required, resulting in an initial pressure loss of more than 0.2MPa, and the resistance increases sharply after impurities are deposited; (3) The problem of MHD (magnetic hydrodynamic) effect cannot be solved, and an additional MHD suppression device is required, which increases the complexity of the system.

[0006] II. Severe MHD effect under strong magnetic fields.

[0007] Liquid lithium lead is a good conductor (conductivity ≈ 10). 6 When the liquid flows in a strong magnetic field (S / m), it cuts the magnetic field lines and generates an induced current. The induced current interacts with the magnetic field to generate a Lorentz force, which hinders the flow of the liquid and creates a huge MHD pressure drop.

[0008] For a rectangular pipe with a conductive wall, the MHD voltage drop gradient Approximately:

[0009] in, △P For pressure drop, L For the length of the pipe, σ f For fluid conductivity, B The magnetic field strength, u For flow rate, It is a Hartmann number.

[0010] According to the formula, under the conditions of a 5T magnetic field, a flow velocity of 1m / s, and a DN50 stainless steel pipe, the pressure drop of MHD can reach more than 15MPa; under a 14T magnetic field, the pressure drop of MHD will exceed 100MPa, which is far greater than the head of the liquid metal circulating pump, which is completely unacceptable in engineering.

[0011] One existing MHD suppression technology involves an insulating coating: applying ceramic coatings such as Al2O3 or Er2O3 to the inner wall of the pipe. However, the coating and the metal substrate have significantly different coefficients of thermal expansion, making them prone to cracking and flaking under thermal cycling and lithium-lead corrosion. Liquid metal then penetrates the metal substrate through these cracks, leading to insulation failure. Experiments show that after 1000 hours of operation in lithium-lead at 500°C or higher, the insulation resistance of the Al2O3 coating decreases by three orders of magnitude, and the MHD suppression rate drops from 60% to below 30%.

[0012] Another existing MHD suppression technology is the Dense Flow Channel Injector (FCI) technology: This technology uses SiC_f / SiC composite materials to create a dense, insulated insert, isolating the liquid metal from the metal pipe. Its MHD suppression principle utilizes the complete electrical insulation of ceramics to fundamentally block the closed loop of induced current in the pipe wall, achieving an MHD suppression rate of 85%~90%. However, Dense FCI lacks filtration functionality, requiring an additional independent filter, resulting in a system with numerous components, high complexity, and high cost.

[0013] Currently, there is no device that can simultaneously solve the two core problems of solid impurity contamination and MHD effect in liquid lithium-lead circuits. Summary of the Invention

[0014] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, one objective of this invention is to propose an integrated insulated flow channel device with filtration function, which can significantly reduce MHD voltage drop while simultaneously achieving a filtration efficiency of ≥99% for solid impurities larger than 10μm in liquid metal circuits. It possesses significant advantages such as simple structure, high reliability, low cost, and long lifespan.

[0015] According to a first aspect of the present invention, an integrated insulating flow channel device with filtration function includes a porous ceramic filter element, a metallized brazed sealing assembly, and a metal shell arranged sequentially from the inside to the outside in the radial direction; wherein, the porous ceramic filter element includes a porous filter element body and an annular dense edge disposed on the outer periphery of the porous filter element body, the porous filter element body has a three-dimensional interconnected pore structure, and the porous filter element body and the annular dense edge are integrally formed; the metallized brazed sealing assembly is sealingly connected between the annular dense edge and the metal shell.

[0016] Compared with the prior art, the integrated insulated flow channel device 1000 with filtering function according to the first aspect embodiment of the present invention has the following advantages: I. Significantly simplified system structure: The dual functions of MHD suppression and impurity filtration are achieved in one device, eliminating the need for separate filters and connecting pipes, reducing the number of loop components by more than 40%, and significantly reducing system complexity and cost.

[0017] II. Significant and Long-Term Stable MHD Suppression: Based on the MHD theory of porous media, the insulating porous ceramic filter element structure can significantly increase the resistance of the induced current loop inside the liquid metal, thereby significantly reducing the total MHD voltage drop. Theoretically predicted suppression rate can reach 85%~90%, which is basically consistent with the level of traditional dense FCI. Due to the use of an integral ceramic structure, there is no problem of coating peeling failure, and the MHD suppression performance remains stable within the 30-year design life.

[0018] 3. High filtration efficiency and strong dirt holding capacity: The filtration efficiency for solid impurities larger than 10μm is ≥99%, the dirt holding capacity is more than 3 times that of a single-pore filter, the pressure loss increases slowly, and the maintenance cycle is extended from 6 months to more than 3 years.

[0019] IV. Excellent corrosion resistance and no electrochemical corrosion: For example, the corrosion rate of porous silicon nitride ceramics in flowing liquid lithium-lead at 500℃ is <0.08μm / year, which is more than 15 times lower than that of 316H stainless steel. The ceramics are completely electrically insulating, thus completely eliminating the problem of electrochemical corrosion between different metals.

[0020] V. Low activation characteristics, meeting the safety requirements of fusion reactors: The porous ceramic filter element will not produce high-activity, long-half-life nuclides under neutron irradiation conditions, which helps to reduce the difficulty of radioactive waste disposal.

[0021] VI. High-pressure reliable sealing: The annular dense edge and the metal shell are sealed and connected by the metallized brazed sealing assembly to achieve a composite seal, which solves the high-pressure sealing problem between the porous ceramic filter element and the metal shell. The sealing pressure is ≥16MPa, which meets the operating pressure requirement of 15MPa for fusion reactors.

[0022] In some embodiments, the porous ceramic filter element is made of porous silicon nitride or porous silicon carbide, and the porosity of the porous ceramic filter element is 35% to 55%. When the porosity of the porous ceramic filter element is 40% to 55%, it is considered a balanced type, capable of balancing permeability and structural strength; when the porosity of the porous ceramic filter element is 35% to 40%, it is considered a conservative type, prioritizing structural reliability under high-pressure conditions, with a closed-cell rate of <5%.

[0023] In some embodiments, the porous ceramic filter element is divided into an upstream filtration section and a downstream guiding section along the liquid metal flow direction. The pore size of the upstream filtration section decreases gradually along the liquid metal flow direction, while the pore size of the downstream guiding section is uniform and consistent with the pore size at the end of the upstream filtration section. The upstream filtration section is the only functional filtration area, achieving graded interception of solid impurities. The downstream guiding section serves to prevent interfacial disturbances in the liquid metal fluid at abrupt changes in pore size, ensuring smooth flow. Simultaneously, as a redundant guarantee for deep filtration, it intercepts a small amount of small-particle impurities that may pass through the upstream section. Its length design (60%~70%) ensures sufficient flow area even in the event of partial blockage, slowing down the rate of pressure drop increase.

[0024] In some embodiments, the length of the upstream filtration section accounts for 30% to 40% of the total length of the porous ceramic filter element. The pore size of the upstream filtration section decreases linearly from 25 to 30 μm to 12 to 15 μm along the liquid flow direction (specifically, the original pore size decreases linearly from 35 to 40 μm to 22 to 25 μm, and the final effective pore size after depositing the h-BN coating (hexagonal boron nitride coating) decreases linearly from 25 to 30 μm to 12 to 15 μm), thus forming a gradient structure of "coarse at the top and fine at the bottom," which is the only filtration functional area, achieving graded interception of solid impurities. The length of the downstream guiding section accounts for 60% to 70% of the total length of the porous ceramic filter element. The pore size of the downstream guiding section is 12 to 15 μm (specifically, the original pore size is 22 to 25 μm, and the final effective pore size after depositing the h-BN coating is 12 to 15 μm), eliminating eddies and disturbances in the fluid at the abrupt change in pore size, and ensuring smooth flow.

[0025] The porous ceramic filter element employs a gradient pore size high-efficiency filtration principle. The upstream filtration section uses a continuous gradient pore size structure with coarser particles at the top and finer particles at the bottom, achieving staged filtration: large particles larger than 15μm are intercepted on the uppermost surface of the filter element, medium-sized particles (5-15μm) are intercepted in the shallow inner layer of the filter element, and fine particles smaller than 5μm pass through the filter element with the liquid metal. This structure avoids the surface filter cake clogging problem that easily occurs with single-pore size structures, significantly improving dirt-holding capacity and service life. The downstream flow guiding section uses a uniform pore size consistent with the end of the upstream filtration section, eliminating eddies and disturbances at abrupt changes in pore size, ensuring smooth flow.

[0026] In some embodiments, the porous ceramic filter element has a volume resistivity ≥1×10⁻⁶ at 300°C. 14 Ω cm is a complete electrical insulator, which fundamentally blocks the closed loop of induced current in the tube wall and achieves suppression of the MHD effect.

[0027] In some embodiments, all surfaces (including the inner pore surfaces) of the porous ceramic filter element are coated with a hexagonal boron nitride coating to increase the contact angle between liquid lithium lead and ceramic from about 130° to 145° to over 150°.

[0028] In some embodiments, the thickness of the hexagonal boron nitride coating is 5~6 μm.

[0029] In some embodiments, the thickness of the annular dense edge is 8-10 mm, and the density is >99.5%. The annular dense edge can prevent the liquid metal conductor in the three-dimensional interconnected holes of the porous filter body located on its radially inner side from contacting the metallized brazed sealing assembly and the metal shell on its radially outer side. The induced current cannot form a closed loop through the metallized brazed sealing assembly and the metal shell, thus achieving complete insulation. In addition, the annular dense edge is also used for metallization sealing.

[0030] In some embodiments, the metal housing is made of 316H stainless steel, low-activation ferritic steel, or martensitic steel, and the downstream section of the metal housing has a step for positioning the porous ceramic filter element.

[0031] In some embodiments, the metallized brazing sealing assembly includes a metallization layer and a brazing filler layer, the metallization layer being located on the outer peripheral surface of the annular dense edge, and the brazing filler layer being located between the metallization layer and the metal housing.

[0032] In some embodiments, the metallization layer is a Mo-Mn metallization layer, and the solder layer is an AgCuTi solder layer. Thus, the metallized brazing sealing assembly employs a composite sealing technology of "edge densification + Mo-Mn metallization + AgCuTi active brazing" to achieve a high-pressure, reliable seal between the porous ceramic filter element and the metal shell.

[0033] In some embodiments, the metal housing is provided with an inlet flange and an outlet flange. The inlet flange is used to connect to the outlet of the metal housing located upstream of the integrated insulated flow channel device with filtration function in the liquid metal circuit, and the outlet flange is used to connect to the inlet of the metal housing located downstream of the integrated insulated flow channel device with filtration function in the liquid metal circuit.

[0034] The second aspect of the present invention also provides a method for preparing an integrated insulating flow channel device with a filtering function, wherein the integrated insulating flow channel device with a filtering function is the integrated insulating flow channel device with a filtering function according to the first aspect of the present invention.

[0035] A method for preparing an integrated insulating flow channel device with a filtering function according to a second aspect of the present invention includes the following steps: Ceramic slurry preparation: Three ceramic slurries with different initial powder particle sizes were prepared respectively. The three initial powders were α-Si3N4 powder with a particle size of 8~10μm, Y2O3 with a particle size of 5~6μm, and Al2O3 with a particle size of 3~4μm. For each slurry, α-Si3N4 powder, Y2O3 and Al2O3 sintering aid of the corresponding particle size were mixed and ball-milled in anhydrous ethanol medium for 24 hours with a solid-liquid ratio of 1:1.2 to obtain three uniformly mixed ceramic slurries. Spray granulation: Three ceramic slurries were spray granulated separately to obtain three granulated powders. Each granulated powder was then air-classified to obtain coarse powder with a median particle size of 25 μm, medium powder with a median particle size of 18 μm, and fine powder with a median particle size of 14 μm. Compression molding: The coarse powder, the medium powder, and the fine powder are sequentially filled into a graphite mold. After each layer is filled, it is vibrated to compact it. The interlayer bonding surfaces are roughened to enhance the mechanical interlocking between layers. The mixture is then pressed into a green body with a gradient pore size decreasing structure along the metal flow channel direction. Then, a Y2O3-Al2O3-SiO2 densification agent with 15wt% high-purity hexagonal boron nitride microparticles as a high-temperature inert thickener is coated on the outer edge of the green body to obtain a molded green body. Gas pressure co-sintering: The formed green blank is placed in a gas pressure sintering furnace and held at 1750°C for 3.0 hours in a high-purity nitrogen atmosphere of 1.5MPa. By controlling the heating rate and the viscosity of the additives, the penetration depth of the densification additives is controlled within 0.5mm, so as to achieve synchronous sintering of the porous filter element body and the annular dense edge region. Surface coating deposition: Low-pressure chemical vapor deposition technology is used to deposit a hexagonal boron nitride coating on all surfaces of the sintered green body at a deposition temperature of 1200℃ and a deposition time of 2.0 hours. Precision machining: The outer peripheral surface of the annular dense edge region is precision ground to completely remove the high-purity hexagonal boron nitride coating of the annular dense edge region. At the same time, the annular dense edge region is machined to the design size to obtain the annular dense edge. The flatness of the annular dense edge is ≤0.02mm and the surface roughness Ra is ≤1.6μm to obtain the porous ceramic filter element. Metallization brazing seal: Mo-Mn metallization treatment is performed on the outer periphery of the annular dense edge of the porous ceramic filter element, followed by nickel electroplating, and finally vacuum brazing with AgCu28Ti3 active brazing filler metal to the metal shell.

[0036] The integrated insulated flow channel device with filtering function of the first aspect of the present invention can be obtained by the preparation method of the integrated insulated flow channel device with filtering function of the second aspect of the present invention.

[0037] The third aspect of the present invention also proposes an application of an integrated insulating flow channel device with a filtering function; wherein, the integrated insulating flow channel device with a filtering function is the integrated insulating flow channel device with a filtering function according to the first aspect of the present invention.

[0038] The application of the integrated insulated flow channel device with filtering function in the third aspect embodiment of the present invention is as follows: the integrated insulated flow channel device with filtering function is installed on the outlet pipe of the lithium lead cladding of the fusion reactor, located between the circulating pump and the heat exchanger.

[0039] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0040] Figure 1 This is a cross-sectional structural schematic diagram of an integrated insulated flow channel device with filtration function according to an embodiment of the present invention; Figure 2 This is a schematic cross-sectional view of the porous filter element body in the integrated insulated flow channel device with filtration function according to an embodiment of the present invention.

[0041] Figure Labels An integrated insulated flow channel device 1000 with filtration function; a porous ceramic filter element 1; a porous filter element body 101; an annular dense edge 102; an upstream filtration section 103; a downstream flow guiding section 104; a metallized brazed sealing assembly 2; a metal shell 3; an inlet flange 4; and an outlet flange 5. Detailed Implementation

[0042] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0043] The following is combined with Figures 1 to 2 This invention describes an integrated insulated flow channel device 1000 with filtration function, its preparation method, and its application.

[0044] like Figure 1 As shown, the integrated insulated flow channel device 1000 with filtration function of the first aspect of the present invention can be used in the liquid metal loop (such as Pb-17Li eutectic alloy loop) of a tokamak-type fusion reactor (3~14T strong magnetic field). It is installed on the outlet pipe of the lithium-lead cladding of the fusion reactor and located between the circulating pump and the heat exchanger. It can also be used in related systems of fourth-generation lead-based fast reactors and sodium-cooled fast reactors. It can achieve efficient filtration of solid impurities in the liquid metal loop while maintaining the MHD suppression effect that is basically the same as that of the traditional dense flow channel plug (FCI).

[0045] like Figure 1 As shown, the integrated insulating flow channel device 1000 with filtering function according to the first aspect embodiment of the present invention includes a porous ceramic filter element 1, a metallized brazed sealing assembly 2 and a metal shell 3 arranged sequentially from the inside to the outside in the radial direction.

[0046] The porous ceramic filter element 1 includes a porous filter element body 101 and an annular dense edge 102 disposed on the outer periphery of the porous filter element body 101. The porous filter element body 101 has a three-dimensional interconnected pore structure, which can effectively filter solid impurities in the liquid metal in the liquid metal circuit and has a strong dirt-holding capacity. The annular dense edge 102 can prevent the liquid metal (the liquid metal is a conductor) in the three-dimensional interconnected pores of the porous filter element body 101 located on its radial inner side from contacting the metallized brazed sealing assembly 2 and the metal shell 3 on its radial outer side. The induced current cannot form a closed circuit through the metallized brazed sealing assembly 2 and the metal shell 3, thus playing a role in complete insulation. The MHD pressure drop suppression rate of the porous ceramic filter element 1 can reach 85%~90%, which is basically consistent with the level of traditional dense FCI, and the liquid metal pressure loss increases slowly, effectively and significantly extending the maintenance cycle. The porous filter element body 101 and the annular dense edge 102 are integrally molded parts, such as integrally sintered parts, without boundary splicing. Since the porous ceramic filter element 1 adopts an integral ceramic structure, there is no problem of the annular dense edge 102 falling off and failing, and the MHD suppression performance remains stable within the 30-year design life. The metallized brazed sealing assembly 2 is sealed between the annular dense edge 102 and the metal shell 3, that is, the metallized brazed sealing assembly 2 is sealed to both the annular dense edge 102 and the metal shell 3, achieving a high-pressure reliable seal and solving the high-pressure sealing problem between the porous ceramic filter element 1 and the metal shell 3. The sealing pressure is ≥16MPa, which meets the operating pressure requirement of up to 15MPa for fusion reactors.

[0047] Compared with the prior art, the integrated insulated flow channel device 1000 with filtering function according to the first aspect embodiment of the present invention has the following advantages: I. Significantly simplified system structure: The dual functions of MHD suppression and impurity filtration are achieved in one device, eliminating the need for separate filters and connecting pipes, reducing the number of loop components by more than 40%, and significantly reducing system complexity and cost.

[0048] II. Significant and Long-Term Stable MHD Suppression: Based on the MHD theory of porous media, the insulating porous ceramic filter element 1 can significantly increase the resistance of the induced current loop inside the liquid metal, thereby significantly reducing the total MHD voltage drop. Theoretically predicted suppression rate can reach 85%~90%, which is basically consistent with the level of traditional dense FCI. Due to the use of an integral ceramic structure, there is no problem of coating peeling failure, and the MHD suppression performance remains stable within the 30-year design life.

[0049] 3. High filtration efficiency and strong dirt holding capacity: The filtration efficiency for solid impurities larger than 10μm is ≥99%, the dirt holding capacity is more than 3 times that of a single-pore filter, the pressure loss increases slowly, and the maintenance cycle is extended from 6 months to more than 3 years.

[0050] IV. Excellent corrosion resistance and no electrochemical corrosion: For example, the corrosion rate of porous silicon nitride ceramics in flowing liquid lithium-lead at 500℃ is <0.08μm / year, which is more than 15 times lower than that of 316H stainless steel. The ceramics are completely electrically insulating, thus completely eliminating the problem of electrochemical corrosion between different metals.

[0051] V. Low activation characteristics, meeting the safety requirements of fusion reactors: The porous ceramic filter element 1 will not produce high-activity, long-half-life nuclides under neutron irradiation conditions, which helps to reduce the difficulty of radioactive waste disposal.

[0052] VI. High-pressure reliable sealing: The annular dense edge 102 and the metal shell 3 are sealed by the metallized brazed sealing assembly 2 to achieve composite sealing, which solves the high-pressure sealing problem between the porous ceramic filter element 1 and the metal shell 3. The sealing pressure is ≥16MPa, which meets the operating pressure requirement of 15MPa for fusion reactors.

[0053] In some embodiments, the porous ceramic filter element 1 is made of porous silicon nitride or porous silicon carbide. This is because: on the one hand, porous silicon nitride or porous silicon carbide has high strength, high temperature resistance, excellent corrosion resistance, and no electrochemical corrosion. For example, the corrosion rate of porous silicon nitride ceramics in flowing liquid lithium-lead at 500°C is <0.08 μm / year, which is more than 15 times lower than that of 316H stainless steel. Porous silicon nitride ceramics or porous silicon carbide ceramics are completely electrically insulating, completely eliminating the problem of electrochemical corrosion between different metals. On the other hand, its low activation characteristics meet the safety requirements of fusion reactors. Specifically, silicon nitride and silicon carbide are widely considered to be low-activation material systems that do not produce high-activity, long-half-life nuclides under neutron irradiation conditions, which helps to reduce the difficulty of radioactive waste disposal.

[0054] The porosity of the porous ceramic filter element 1 is 35%~55%. Among them, when the porosity of the porous ceramic filter element is 40%~55%, it is a balanced type, which can take into account both permeability and structural strength; when the porosity of the porous ceramic filter element is 35%~40%, it is a conservative type, which prioritizes ensuring structural reliability under high pressure conditions, and the closed pore rate is <5%.

[0055] In some embodiments, such as Figure 1 and Figure 2As shown, the porous ceramic filter element 1 is divided into an upstream filtration section 103 and a downstream guide section 104 along the direction of liquid metal flow. The pore size of the upstream filtration section decreases gradually along the direction of liquid metal flow. The upstream filtration section 103 is the only functional filtration area, capable of intercepting solid impurities in stages. The downstream guide section 104 has a uniform pore size, consistent with the pore size at the end of the upstream filtration section. The function of the downstream guide section 104 is to prevent interface disturbances in the liquid metal fluid at the abrupt change in pore size, ensuring smooth flow. Simultaneously, as a redundant guarantee for deep filtration, it intercepts a small amount of small-particle impurities that may pass through the upstream section. Its length design (60%~70%) ensures sufficient flow area even in the event of partial blockage, slowing down the rate of pressure drop increase.

[0056] In some embodiments, the length of the upstream filtration section 103 accounts for 30% to 40% of the total length of the porous ceramic filter element 1. The pore size of the upstream filtration section 103 linearly decreases from 25 to 30 μm to 12 to 15 μm along the liquid flow direction (specifically, the original pore size linearly decreases from 35 to 40 μm to 22 to 25 μm, and the final effective pore size after depositing the h-BN coating linearly decreases from 25 to 30 μm to 12 to 15 μm), thus forming a "coarse at the top and fine at the bottom" structure (i.e., the upstream filtration section 103 exhibits a finer particle size due to the granulation powder from upstream to downstream). The gradient structure (with a decreasing pore size gradient from upstream to downstream) is the only functional filtration zone, enabling graded interception of solid impurities. The downstream guide section 104 accounts for 60% to 70% of the total length of the porous ceramic filter element 1, and its pore size is 12 to 15 μm (specifically, the original pore size of the downstream guide section 104 is 22 to 25 μm, and the final effective pore size after depositing the h-BN coating is 12 to 15 μm). The function of the downstream guide section 104 is to avoid interfacial disturbances at the pore size abrupt change and ensure smooth flow.

[0057] In this embodiment, the porous ceramic filter element 1 employs a gradient pore size high-efficiency filtration principle. The upstream filtration section 103 adopts a continuous gradient pore size structure with coarser particles at the top and finer particles at the bottom, achieving staged filtration: large particles larger than 15μm are intercepted on the uppermost surface of the filter element, medium-sized particles of 5-15μm are intercepted in the shallow inner layer of the filter element, and fine particles smaller than 5μm pass through the filter element with the liquid metal. This structure avoids the surface filter cake clogging problem that easily occurs with single-pore size structures, significantly improving dirt holding capacity and service life. The downstream guide section 104 adopts a uniform pore size consistent with the end section of the upstream filtration section 103, eliminating eddies and disturbances in the fluid at the abrupt change in pore size, ensuring smooth flow.

[0058] In some embodiments, the volume resistivity of the porous ceramic filter element 1 at 300°C is ≥1×10⁻⁶. 14 Ω The volume resistivity was measured using the high-temperature insulation resistance test method in GB / T 31838.2-2019. It is a complete electrical insulator, which fundamentally blocks the closed loop of induced current in the tube wall and achieves suppression of the MHD effect.

[0059] In some embodiments, all surfaces (including the inner surface of the pores) of the porous ceramic filter element 1 are coated with a hexagonal boron nitride coating to stably increase the contact angle between liquid lithium lead and ceramic from about 130°~145° to more than 150°, thereby reducing the wetting and penetration of lithium lead.

[0060] In some embodiments, the thickness of the hexagonal boron nitride coating is 5~6μm, which is economical and can stably increase the contact angle between liquid lithium lead and ceramic from about 130°~145° to more than 150°, reducing the wetting and penetration of lithium lead.

[0061] In some embodiments, the thickness of the annular dense edge 102 is 8-10 mm, and the density is >99.5%. This annular dense edge 102 prevents the liquid metal conductor in the three-dimensional interconnected holes of the porous filter body 101 located radially inward from contacting the metallized brazed sealing assembly 2 and the metal shell 3 radially outward. The induced current cannot form a closed loop through the metallized brazed sealing assembly 2 and the metal shell 3, thus providing complete insulation. The porous ceramic filter element 1 is a complete electrical insulator. Substituting into the MHD voltage drop formula, it can be seen that the MHD voltage drop caused by the conductivity of the metal shell 3 is completely eliminated. The MHD voltage drop suppression rate of the porous ceramic filter element 1 can reach 85%-90%, which is basically consistent with the level of traditional dense FCI. Furthermore, the annular dense edge 102 is also used for metallization sealing.

[0062] In some embodiments, the metal housing 3 is made of 316H stainless steel, low-activation ferritic steel or martensitic steel, and the downstream section of the metal housing 3 is provided with a step for positioning the porous ceramic filter element 1.

[0063] In some embodiments, the metallized brazing sealing assembly includes a metallized layer and a brazing filler layer. The metallized layer is located on the outer peripheral surface of the annular dense edge 102, and the brazing filler layer is located between the metallized layer and the metal housing 3. This achieves a high-pressure, reliable seal between the porous ceramic filter element 1 and the metal housing 3, with a sealing pressure ≥16 MPa.

[0064] In some embodiments, the metallization layer is a Mo-Mn metallization layer, and the solder layer is an AgCuTi solder layer. Thus, the metallized brazing sealing assembly 2 adopts a composite sealing technology of "edge densification + Mo-Mn metallization + AgCuTi active brazing" to achieve a high-pressure reliable seal between the porous ceramic filter element 1 and the metal shell 3, with a sealing pressure ≥16MPa.

[0065] In some embodiments, the metal housing 3 is provided with an inlet flange 4 and an outlet flange 5. The inlet flange 4 is used to connect (e.g., weld) to the outlet of the metal housing located upstream of the integrated insulated flow channel device 1000 with filtration function in the liquid metal circuit. The outlet flange 5 is used to connect (e.g., weld) to the inlet of the metal housing located downstream of the integrated insulated flow channel device 1000 with filtration function in the liquid metal circuit.

[0066] Two specific embodiments are given below to illustrate the integrated insulated flow channel device 1000 with filtering function according to the first aspect of the present invention.

[0067] Example 1 is an integrated insulated flow channel device 1000 with filtration function based on balanced DN50 porous silicon nitride.

[0068] This embodiment is an integrated insulating flow channel device 1000 with filtration function that is matched with the lithium-lead cladding loop of a fusion reactor. It adopts a balanced porosity design to take into account both permeability and structural strength.

[0069] Overall parameters of the device: nominal diameter DN50, nominal pressure 16MPa, design temperature 550℃, design magnetic field strength 5T. The metal shell 3 is made of 316H stainless steel. The inlet flange 4 and outlet flange 5 are custom flanges adapted to high-temperature conditions. According to ASME B16.5 standard, the allowable working pressure of this material flange at 550℃ is not less than 16MPa.

[0070] The porous ceramic filter element 1 is an integral cylindrical structure with a diameter of 48 mm and a length of 150 mm, made of porous silicon nitride. The upstream filtration section 103 is 45 mm long (30% of the total length), with an initial pore size linearly decreasing from 38 μm to 24 μm along the liquid metal flow direction. After depositing a 5 μm thick h-BN coating, the final effective pore size linearly decreases from 28 μm to 14 μm. The downstream flow guiding section 104 is 105 mm long (70% of the total length), with a uniform initial pore size of 24 μm. After coating deposition, the final effective pore size is 14 μm. The overall porosity is 48%, the closed-pore rate is 3.2%, and the volume resistivity at 300℃ is 1.5 × 10¹. 4 Ω The volume resistivity was measured using the high-temperature insulation resistance test method in GB / T31838.2-2019. The surface of the filtration area of ​​the porous ceramic filter element 1 is coated with a 6μm thick h-BN coating, while the dense edge area is not coated. The outer edge of the porous ceramic filter element 1 has a pre-reserved annular dense edge 102 with a radial width of 8mm and a density of 99.5%.

[0071] The structure of the metallized brazed sealing assembly 2: The densified edge region is sequentially coated with a 60μm thick Mo-Mn metallization layer and a 7μm thick electroplated nickel layer, and is brazed to the metal shell 3 by AgCu28Ti3 active brazing filler metal, with a brazing filler metal layer thickness of 60μm.

[0072] Theoretical performance expectations: (Conditions: 5T magnetic field, 300℃ liquid Pb-17Li, flow rate 1m / s): Filtration efficiency of solid impurities larger than 10μm not less than 99%; MHD pressure drop suppression rate not less than 85% (compared to 316H stainless steel pipes of the same size); steady-state hydraulic pressure drop not greater than 0.085MPa; designed dirt holding capacity of 4.2g (cumulative impurity mass when pressure loss increases by 50%); corrosion rate not greater than 0.06μm / year after immersion in lithium lead at 500℃ for 1000 hours; hydrostatic sealing test pressure not less than 16MPa (no leakage after 30 minutes of pressure holding); thermal cycle life not less than 1500 cycles (200~500℃, no cracks, no leakage).

[0073] Example 2 is an integrated insulated flow channel device 1000 with filtration function based on conservative DN50 porous silicon nitride.

[0074] The difference between Example 2 and Example 1 is that Example 2 adopts a conservative porosity design, which prioritizes the structural reliability under high pressure conditions and is suitable for high pressure circuits above 10MPa.

[0075] The overall porosity of the porous ceramic filter element 1 in Example 2 is 40%, and the remaining structural parameters are exactly the same as those in Example 1.

[0076] Theoretical performance expectations (under the same conditions as Example 1): filtration efficiency of solid impurities larger than 10μm is not less than 99%; MHD pressure drop suppression rate is not less than 88.5%; steady-state hydraulic pressure drop is not greater than 0.085MPa; designed dirt holding capacity is 3.8g; hydrostatic pressure sealing test pressure is not less than 17MPa (no leakage after 30 minutes of pressure holding).

[0077] Compared with a DN50 stainless steel pipe with a 10μm pore size 316H stainless steel wire mesh filter and an inner wall coated with a 50μm Al2O3 coating, the stainless steel wire mesh filter has the following problems: the initial MHD pressure drop suppression rate is about 63%; after 1000 hours of operation, it drops to about 32% (coating peels off); after immersion in lithium lead at 500℃ for 1000 hours, the corrosion rate is extremely high.

[0078] Compared to traditional dense FCI solutions, which lack filtration capabilities and require an additional independent filter, this approach offers a more comprehensive solution.

[0079] By comparison, it can be seen that the MHD suppression effect of the integrated insulating flow channel device 1000 with filtering function in the first aspect embodiment of the present invention is basically equivalent to that of traditional dense FCI, but it adds a high-efficiency filtering function and eliminates the need for a separate filter; its overall performance is significantly better than the traditional "filter + insulating coating" combination scheme.

[0080] The second aspect of the present invention also provides a method for preparing an integrated insulating flow channel device 1000 with a filtering function, wherein the integrated insulating flow channel device 1000 with a filtering function is the integrated insulating flow channel device 1000 with a filtering function according to the first aspect of the present invention.

[0081] The preparation method of the integrated insulated flow channel device 1000 with filtration function according to a second aspect embodiment of the present invention includes the following steps: Ceramic slurry preparation: Three ceramic slurries with different initial powder particle sizes were prepared respectively. The three initial powders were α-Si3N4 powder with a particle size of 8~10μm, Y2O3 with a particle size of 5~6μm, and Al2O3 with a particle size of 3~4μm. For each slurry, α-Si3N4 powder, Y2O3 and Al2O3 sintering aid of the corresponding particle size were mixed and ball-milled in anhydrous ethanol medium for 24 hours with a solid-liquid ratio of 1:1.2 to obtain three uniformly mixed ceramic slurries.

[0082] Spray granulation: Three ceramic slurries were spray granulated separately to obtain three granulated powders. Each granulated powder was then air-classified to obtain coarse powder with a median particle size of 25 μm, medium powder with a median particle size of 18 μm, and fine powder with a median particle size of 14 μm.

[0083] Compression molding: Coarse powder, medium powder, and fine powder are sequentially filled into a graphite mold. After each layer is filled, it is vibrated to compact it. The interlayer bonding surface is roughened to enhance the mechanical interlocking between layers. The mold is then pressed into a green body with a gradient pore size decreasing structure along the metal flow channel. Then, a Y2O3-Al2O3-SiO2 densification agent with 15wt% high-purity hexagonal boron nitride microparticles as a high-temperature inert thickener is coated on the outer edge of the green body to obtain the molded green body.

[0084] Gas pressure co-sintering: The formed green blank is placed in a gas pressure sintering furnace and held at 1750℃ for 3.0 hours in a high-purity nitrogen atmosphere of 1.5MPa. By controlling the heating rate and the viscosity of the additives, the penetration depth of the densification additives is controlled within 0.5mm, so as to achieve synchronous sintering of the porous filter element body 101 and the annular dense edge region.

[0085] Surface coating deposition: Low-pressure chemical vapor deposition technology is used to deposit a hexagonal boron nitride coating on all surfaces of the sintered green body at a deposition temperature of 1200℃ and a deposition time of 2.0 hours.

[0086] Precision machining: The outer peripheral surface of the annular dense edge region is precision ground to completely remove the high-purity hexagonal boron nitride coating of the annular dense edge region. At the same time, the annular dense edge region is machined to the design size to obtain the annular dense edge 102. The flatness of the annular dense edge 102 is guaranteed to be ≤0.02mm and the surface roughness Ra≤1.6μm to obtain the porous ceramic filter element 1.

[0087] Metallized brazing seal: Mo-Mn metallization is performed on the outer periphery of the annular dense edge 102 of the porous ceramic filter element 1, followed by nickel electroplating, and finally vacuum brazing with AgCu28Ti3 active brazing filler metal to the metal shell 3. By adopting the composite sealing technology of "dense edge + Mo-Mn metallization + AgCuTi active brazing", a high-pressure reliable seal between the ceramic filter element and the metal shell 3 is achieved, with a sealing pressure ≥16MPa.

[0088] The integrated insulated flow channel device 1000 with filtering function of the first aspect embodiment of the present invention can be obtained by the preparation method of the integrated insulated flow channel device 1000 with filtering function of the second aspect embodiment of the present invention.

[0089] In some embodiments, the specific steps of metallization brazing sealing are as follows: Mo-Mn metallization treatment is performed in the densified edge region of the filter element (sintering at 1425~1435℃ in a wet hydrogen atmosphere for 11~13 minutes), followed by nickel electroplating (7~7.5μm thickness), and finally vacuum brazing is performed with AgCu28Ti3 active brazing filler metal to the metal shell 3 (holding at 865~875℃ for 10~11 minutes, vacuum degree ≤5×10). -4 Pa).

[0090] The third aspect of the present invention also proposes an application of an integrated insulating flow channel device 1000 with a filtering function; wherein, the integrated insulating flow channel device 1000 with a filtering function is the integrated insulating flow channel device 1000 with a filtering function according to the first aspect of the present invention.

[0091] The application of the integrated insulating flow channel device 1000 with filtering function in the third aspect embodiment of the present invention is as follows: the integrated insulating flow channel device 1000 with filtering function is installed on the outlet pipe of the lithium lead cladding of the fusion reactor, located between the circulating pump and the heat exchanger.

[0092] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An integrated insulated flow channel device with filtration function, characterized in that, The device includes a porous ceramic filter element, a metallized brazed sealing assembly, and a metal housing arranged radially from the inside out. The porous ceramic filter element comprises a porous filter element body and an annular dense edge disposed on the outer periphery of the porous filter element body. The porous filter element body has a three-dimensional interconnected pore structure, and the porous filter element body and the annular dense edge are integrally formed. The metallized brazed sealing assembly is sealingly connected between the annular dense edge and the metal housing. The porous ceramic filter element is divided into an upstream filtration section and a downstream guiding section along the direction of liquid metal flow. The pore size of the upstream filtration section decreases gradually along the direction of liquid metal flow. The pore size of the downstream guiding section is uniform and is consistent with the pore size at the end of the upstream filtration section. The pore size of the upstream filtration section decreases linearly from 25~30μm to 12~15μm along the direction of liquid flow; All surfaces of the porous ceramic filter element are coated with a hexagonal boron nitride coating to stably increase the contact angle between liquid lithium lead and ceramic from 130°~145° to over 150°.

2. The integrated insulated flow channel device with filtration function according to claim 1, characterized in that, The porous ceramic filter element is made of porous silicon nitride or porous silicon carbide, and the porosity of the porous ceramic filter element is 35%~55%.

3. The integrated insulated flow channel device with filtration function according to claim 1, characterized in that, The length of the upstream filtration section accounts for 30% to 40% of the total length of the porous ceramic filter element, and the length of the downstream guide section accounts for 60% to 70% of the total length of the porous ceramic filter element.

4. The integrated insulated flow channel device with filtration function according to claim 1, characterized in that, The porous ceramic filter element has a volume resistivity ≥1×10⁻⁶ at 300℃. 14 Ω cm.

5. The integrated insulated flow channel device with filtration function according to claim 1, characterized in that, The thickness of the hexagonal boron nitride coating is 5~6μm.

6. The integrated insulated flow channel device with filtration function according to claim 1, characterized in that, The thickness of the annular dense edge is 8~10mm, and the density is >99.5%.

7. The integrated insulated flow channel device with filtration function according to claim 1, characterized in that, The metal casing is made of 316H stainless steel, low-activation ferritic steel, or martensitic steel.

8. The integrated insulated flow channel device with filtration function according to claim 1, characterized in that, The metallized brazing sealing assembly includes a metallized layer and a brazing filler layer. The metallized layer is located on the outer peripheral surface of the annular dense edge, and the brazing filler layer is located between the metallized layer and the metal shell.

9. The integrated insulated flow channel device with filtration function according to claim 8, characterized in that, The metallization layer is a Mo-Mn metallization layer, and the solder layer is an AgCuTi solder layer.

10. The integrated insulated flow channel device with filtration function according to claim 1, characterized in that, The metal casing is provided with an inlet flange and an outlet flange.

11. A method for preparing an integrated insulated flow channel device with filtration function as described in any one of claims 1-10, characterized in that, Includes the following steps: Ceramic slurry preparation: Three ceramic slurries with different initial powder particle sizes were prepared respectively. The three initial powders were α-Si3N4 powder with a particle size of 8~10μm, Y2O3 with a particle size of 5~6μm, and Al2O3 with a particle size of 3~4μm. For each slurry, α-Si3N4 powder, Y2O3 and Al2O3 sintering aid of the corresponding particle size were mixed and ball-milled in anhydrous ethanol medium for 24 hours with a solid-liquid ratio of 1:1.2 to obtain three uniformly mixed ceramic slurries. Spray granulation: Three ceramic slurries were spray granulated separately to obtain three granulated powders. Each granulated powder was then air-classified to obtain coarse powder with a median particle size of 25 μm, medium powder with a median particle size of 18 μm, and fine powder with a median particle size of 14 μm. Compression molding: The coarse powder, the medium powder, and the fine powder are sequentially filled into a graphite mold. After each layer is filled, it is vibrated to compact it. The interlayer bonding surfaces are roughened to enhance the mechanical interlocking between layers. The mixture is then pressed into a green body with a gradient pore size decreasing structure along the metal flow channel direction. Then, a Y2O3-Al2O3-SiO2 densification agent with 15wt% high-purity hexagonal boron nitride microparticles as a high-temperature inert thickener is coated on the outer edge of the green body to obtain a molded green body. Gas pressure co-sintering: The formed green blank is placed in a gas pressure sintering furnace and held at 1750°C for 3.0 hours in a high-purity nitrogen atmosphere of 1.5MPa. By controlling the heating rate and the viscosity of the additives, the penetration depth of the densification additives is controlled within 0.5mm, so as to achieve synchronous sintering of the porous filter element body and the annular dense edge region. Surface coating deposition: Low-pressure chemical vapor deposition technology is used to deposit a hexagonal boron nitride coating on all surfaces of the sintered green body at a deposition temperature of 1200℃ and a deposition time of 2.0 hours. Precision machining: The outer peripheral surface of the annular dense edge region is precision ground to completely remove the high-purity hexagonal boron nitride coating of the annular dense edge region. At the same time, the annular dense edge region is machined to the design size to obtain the annular dense edge. The flatness of the annular dense edge is ≤0.02mm and the surface roughness Ra is ≤1.6μm to obtain the porous ceramic filter element. Metallization brazing seal: Mo-Mn metallization treatment is performed on the outer periphery of the annular dense edge of the porous ceramic filter element, followed by nickel electroplating, and finally vacuum brazing with AgCu28Ti3 active brazing filler metal to the metal shell.

12. An application of an integrated insulated flow channel device with filtration function as described in any one of claims 1-10, characterized in that, The integrated insulated flow channel device with filtration function is installed on the outlet pipe of the lithium-lead cladding of the fusion reactor, located between the circulating pump and the heat exchanger.

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