Integrated Electrical Conductor

Abstract

The main object of the present invention is an electrical conductor (70) comprising an assembly (72) comprising a main conductive core (74) made of a first metallic material and a sheath (79) covering the main conductive core (74) and made of a second metallic material having an electrical resistivity greater than that of the first metallic material, and a contact pin (78) connected to a first end (72a) of the assembly (72), the contact pin (78) comprising a conductive core of the contact pin and a protective housing for the contact pin, characterized in that the contact pin (78) is at least partially made of the second metallic material and the conductive core (73) and the main conductive core (74) of the contact pin are made from a single piece.

Description

[Technical Field]

[0001] The present invention relates to the general field of High Temperature Electrolysis (HTE), in particular High Temperature Steam Electrolysis (HTSE), carbon dioxide (CO2) electrolysis, and also high temperature co-electrolysis of steam and carbon dioxide (CO2).

[0002] More particularly, the invention relates to the field of high-temperature electrochemical devices such as solid oxide electrolysis cells, usually referred to by the acronym SOEC (Solid Oxide Electrolysis Cell), and high-temperature solid oxide fuel cells, usually referred to by the acronym SOFC (Solid Oxide Fuel Cell), but also to high-temperature co-electrolyzers of water vapor with carbon dioxide, high-temperature electrolyzers, and reversible fuel cell systems or so-called intermediate-temperature fuel cells or electrolyzers of around 400°C, also known as PCFC (Proton Ceramic Fuel Cell), short for Protonic Ceramic Fuel Cell.

[0003] More generally, the invention therefore relates to the field of solid oxide cell stacks of the SOEC / SOFC type operating at high temperatures, which stacks can operate at atmospheric pressure or under elevated pressure.

[0004] Beyond such SOEC / SOFC type solid oxide cell stacks, the present invention relates to any system requiring electrical conduction in an oxidizing environment at high temperatures or under conditions that lead to rapid degradation of conductive materials.

[0005] More particularly, the present invention relates to the supply of electrical current to a stack of electrochemical cells in a hot zone. [Background technology]

[0006] In the context of high-temperature solid oxide electrolysis cells (SOECs), this includes converting water vapor (H2O) to dihydrogen (H2) or other fuels, such as methane (CH4), natural gas, biogas, and dioxygen (O2), and / or converting carbon dioxide (CO2) to carbon monoxide (CO) and dioxygen (O2), within the same electrochemical device, by means of an electric current. In the context of high-temperature solid oxide fuel cells (SOFCs), the operation is typically reversed by providing dihydrogen (H2) and dioxygen (O2) from air and natural gas, i.e., methane (CH4), to generate electric current and heat. For simplicity, the following description prioritizes the operation of high-temperature solid oxide electrolysis cells (SOECs) performing electrolysis of water vapor. However, this operation is also applicable to the electrolysis of carbon dioxide (CO2) and even the high-temperature co-electrolysis (HTSE) of carbon dioxide (CO2) and water vapor. Additionally, this operation is transferable to the case of high-temperature solid oxide fuel cells (SOFCs).

[0007] As known per se, a high temperature steam (HO) electrolyser, or HTSE electrolyser, comprises a stack of several basic solid oxide electrochemical cells. Referring to Figure 1, the solid oxide cell 10, or "SOC" (Solid Oxide Cell), comprises, inter alia, a) a first porous conductive electrode 12, i.e., cathode, designed to be supplied with water vapor for the production of dihydrogen, b) a second porous conductive electrode 14, i.e., anode, to which dioxygen (O) produced by electrolysis of water injected at the cathode escapes, and c) a solid oxide (dense electrolyte) membrane 16 sandwiched between the cathode 12 and anode 14, the membrane 16 being anionically conductive at high temperatures, typically above 600°C.

[0008] By heating the cell 10 to at least this temperature and injecting a current I into the anode 14, reduction of water on the cathode 12 occurs, which produces dihydrogen (H2) at the cathode 12 and dioxygen (O2) at the anode 14.

[0009] A stack 20 of such cells, intended for producing large amounts of hydrogen, is shown in schematic form in Figure 2. In particular, the cells 10 are stacked on top of each other, separated by interconnecting plates 18 or interconnectors. The function of these plates is both to ensure electrical continuity between the different electrodes of the cells 10, thus allowing them to be electrically connected in series, and to distribute the various gases necessary for the functioning of the cells, as well as, if applicable, a carrier gas that helps to evacuate the electrolysis products and / or thermally manage the stack.

[0010] To do this, the plate 18 is supplied with a constant water vapor flow D regulated by a controllable valve 24. H2O The plates 18 are connected to a water vapor source 22 for injecting this water vapor into the cathode of the cell 10 according to the method described above. The plates 18 are also connected to a gas manifold 26 for collecting gases from the electrolyte. An example of an interconnected plate stack and structure is described, for example, in International Application WO2011 / 110676A1.

[0011] For effective implementation of electrolysis by the stack 20, the stack is brought to a temperature above 600°C, typically between 650°C and 900°C, the gas supply is turned on at a constant flow rate, and a power supply 28 is connected between the two terminals 30, 32 of the stack 20 to circulate a current I.

[0012] The current intensity I is typically on the order of several hundred amperes, which generates large heat losses due to the Joule effect in the electrical conductors. To optimize the energy efficiency of solid oxide electrochemical systems, these heat losses should be limited by specifically developing the electrical conductors, also called "current-carrying conductors" (or "busbars").

[0013] The current carrying conductors in the stack are usually in the form of metal rods. Taking the example of a cylindrical rod, the electrical resistance R is given by the following equation:

[0014]

number

[0015] where ρ is the resistivity of the rod (in Ω m), l is the length of the rod (in m), and S is the cross-sectional area of ​​the rod (in m 2 units).

[0016] Since losses due to the Joule effect are proportional to the resistance R, to limit this effect it is necessary to reduce the electrical resistance of the current-carrying conductors. Therefore, a possible optimization is: Limiting the length of the rod, Increasing the cross-sectional area of ​​the rod; Finding materials with lower resistivity and stability at high temperatures It consists of:

[0017] The first two possibilities generally involve a choice of geometry that depends on the geometry of the electrochemical system. Therefore, constraints exist and / or prior art conductors are already optimized for the electrochemical system. The last point concerns the selection of a bar material with the lowest resistivity to reduce ohmic losses.

[0018] The optimization of this last point has not been given sufficient consideration. In fact, energy efficiency is not paramount for all technological developments in the laboratory. On the other hand, as will be explained later, the current-carrying conductors are immersed in a highly corrosive environment, so the standard solution implemented is to use solid stainless alloy rods, which is therefore the standard solution in all international literature. The resistivity of these rods at room temperature (20°C) is already high, about 75.10 -8 It should be noted that the resistivity increases rapidly with temperature.

[0019] Therefore, at 900°C, which is a high temperature for the functioning of a solid oxide electrolysis cell, the electrical resistance of the stainless steel rod is 117.10 -8Ω·m, which generates very high ohmic losses. These aspects are particularly described in French patent application FR3036840A1.

[0020] However, copper is generally the material recommended for electrical conductors exposed to high current intensities in order to optimize electrical resistivity. Experimental studies carried out by the applicant have made it possible to determine the resistivity curve of copper as a function of temperature and to confirm that the choice of copper allows a reduction in ohmic losses by at least a factor of 10 relative to a reference material over the entire operating temperature range of solid oxide systems.

[0021] However, one of the major constraints that needs to be considered is the corrosion problem associated with the stack environment.

[0022] Referring to FIG. 3, the stack 20 is in fact housed in a so-called "thermal" enclosure, the temperature of which is maintained between 650°C and 900°C under an air flush, and therefore a conventional electrochemical system comprises: For example, the HTSE electrolyzer 20 described in relation to Figures 1 and 2, comprising a set of pipes 52, 54, 56, 58 for supplying and collecting the anode and cathode gases of the electrochemical cells of the electrolyzer. The electrolytic cell 20 is housed in an enclosure 60, the walls of which are penetrated by pipes 52, 54, 56, 58 for connection to gas supply and collection circuits (not shown). The enclosure 60 also includes an air inlet duct 62 and an air outlet duct 64, and the enclosure 60 is sealed throughout, for example against gases and liquids. The duct 62 can be connected to an air supply circuit (not shown) for applying an air flush of the hot zone surrounding the electrolytic cell 20, the flush air being discharged by the outlet duct 64. Two electrical conductors 66, 68 are connected to the terminals 30, 32 of the stack 20 and pass through the enclosure 60 for connection to the current source 28.

[0023] Under these conditions, the two conductors 66, 68 in the form of copper rods, at least partially contained within the enclosure 60, oxidize very rapidly. Additionally, copper is not resistant to oxidation at high temperatures because the oxides formed on the surface do not seal or adhere well enough to protect the underlying metal. Materials known to resist oxidation at high temperatures form much more protective oxides, chromine and / or alumina, and thus chromine and alumina alloys, such as stainless steel and stainless nickel alloys. However, as previously mentioned, these alloys have electrical resistivities such that their use results in significant energy losses.

[0024] High-temperature solid oxide fuel cells (SOFCs) have similar problems. In fact, HTSE electrolyzers and SOFCs are identical structures, differing only in their operating mode: the electrolyzer operates in carbon dioxide (CO2) reduction mode or co-electrolysis mode, i.e., with a cathode input gas mixture consisting of water vapor (HO) and carbon dioxide (CO2). The cathode outlet mixture consists of hydrogen (H2), water vapor (HO), carbon monoxide (CO), and carbon dioxide (CO2). Referring to Figure 4, the electrochemical cells constituting the SOFC have the same elements as the electrolyzer cell (anode 14, cathode 12, electrolyte 16), but the cells of the stack are supplied with a constant flow of dihydrogen at their anodes and dioxygen at their cathodes and are connected to a charge C to transfer the generated current. Therefore, for generated currents of several amperes, the stack has the same problems as the electrolyzer.

[0025] One solution is to protect the copper rod (or any other metal deemed suitable in terms of electrical resistivity) with a coating, such as a chromium or alumina coating, to provide good resistance to oxidation. This poses several problems. First, the seal and performance of the coating on the copper substrate must be guaranteed during heating. It should be noted that copper has a high thermal expansion coefficient, which can lead to large differential thermal stresses that can damage the coating and / or the coating / copper interface. In addition, at the hot end of the rod, an electrical connection to the stack must be made without exposing the copper. Therefore, the connection must be made to the coating without damaging it, which is technically challenging.

[0026] Another solution is to coat the copper rod with a sheath of oxidation-resistant material. In this way, the problem of resistance to thermal expansion differential stresses is solved, since the two materials are not interconnected. Such assemblies (copper + stainless steel sheath) are already known from the prior art for other applications (e.g., in highly acidic environments at low temperatures of 50-80°C), particularly from Chinese document CN202608143U, which describes a copper rod simply threaded into a steel tube. It has been observed that this type of conductor, while satisfactory at and for low temperatures, is not directly suitable for solid oxide systems. Indeed, at high temperatures, poor contact between the conductive core and the sheath results in a deterioration of the electrical contact between the two materials and increased ohmic losses. In other words, the prior art lacks an optimized electrical conduction system capable of accommodating high currents and withstanding large thermal cycles in an oxidizing environment.

[0027] An electrical conductor suitable for currents of several hundred amperes, resistant to oxidation at high temperatures and able to withstand thermal cycles up to 900° C. is known from patent application FR3036840A1. This electrical conductor comprises a rod made of a first metallic material and a sheath made of a second metallic material that completely covers the rod, both of which are welded together using hot isostatic pressing (HIP).

[0028] More specifically, the request proposes forming a circular copper core protected by a sheath of Inconel® 600 steel tube with a connecting terminal, called a "whistle," and a closure cap, also made of Inconel® 600 steel, from which it is evacuated. These components are assembled by TIG (Tungsten Inert Gas) arc welding. The resulting rod then undergoes a hot isostatic pressing (HIP) process, which allows for diffusion welding of dissimilar materials without the addition of filler metal.

[0029] However, this solution has drawbacks, since the copper core stops at the whistle, which is made from Inconel 600. As a result, the current must pass through a long length of material with poor electrical conductivity, which increases the electrical resistance of the current-carrying conductor. [Prior art documents] [Patent documents]

[0030] [Patent Document 1] WO2011 / 110676A1 [Patent Document 2] FR3036840A1 [Patent Document 3] CN202608143U Summary of the Invention [Problem to be solved by the invention]

[0031] SUMMARY OF THE INVENTION It is an object of the present invention to at least partially address the above-mentioned needs and drawbacks associated with prior art embodiments. [Means for solving the problem]

[0032] The object of the present invention is therefore, according to one aspect, to a main conductive core constructed from a first metallic material; A sheath that covers the main conductive core and is made of a second metallic material, particularly stainless steel or a refractory material, having an electrical resistivity greater than that of the first metallic material. an assembly comprising: a contact pin connected to the first end of the assembly, the contact pin comprising a conductive core of the contact pin and a protective housing of the contact pin; Equipped with An electrical conductor characterized in that the connection pin is at least partially made from a second metal material, in particular the protective housing is made from the second metal material, the conductive core of the connection pin is made in particular from the first metal material, and the conductive core of the connection pin and the main conductive core are made from a single part.

[0033] The electrical conductor according to the invention may further comprise one or more of the following characteristics, taken individually or according to all possible technical combinations:

[0034] The electrical conductor may be a rigid electrical conductor. In particular, the main conductive core may be a rigid conductive core.

[0035] A "rigid" electrical conductor, in contrast to a "soft" electrical conductor used to connect to a stack, refers to a conductor that acts mechanically within the main connection and is not necessarily connected to the stack, avoiding the transmission of vibration, expansion, or other parasitic motions between the stack and its environment and allowing potential electrical connections to be made between stacks without mechanical transitions. A rigid electrical conductor has sufficient rigidity to hold itself in place.

[0036] The electrical conductor may comprise a closure cap at least partially constructed from a second metallic material and connected to the second end of the assembly, the closure cap including, inter alia, a central channel for vacuum sealing.

[0037] Additionally, the sheath may include an end piece that contacts the contact pin at the first end of the assembly.

[0038] The conductive core of the contact pin can be inserted into a housing of the contact pin made at least in part from a second metallic material, and the housing and conductive core of the contact pin can be drilled to form a passageway that accommodates a tube made at least in part from the second metallic material.

[0039] The main conductive core and the conductive core of the contact pin made of the first metallic material may be made of copper, nickel, or silver, and / or alloys of copper, nickel, or silver, or any other metal or alloy that is a good electrical conductor, especially any other good conductive metal or alloy that is susceptible to oxidation at high temperatures of about 900°C, such as brass or bronze.

[0040] In addition, the sheath, the housing, any closure cap, and any tube made from a second metallic material may be made from a stainless or refractory metal and / or a metal or refractory alloy, in particular a stainless or refractory steel based on, for example, nickel, chromium, or cobalt, in particular Inconel, for example Inconel 600 or 625, or any other metal or alloy resistant to oxidation at high temperatures, for example 316L stainless steel.

[0041] Furthermore, according to another of its aspects, the present invention also relates to a method for manufacturing an electrical conductor as defined above, characterized in that it comprises a step of manufacturing the conductive core of the contact pin by forging or die cutting.

[0042] The method comprises the following steps: forging or die-cutting the end of a metal rod, in particular of cylindrical shape and circular cross section, made from a first metallic material, to form the conductive core of the contact pin; rolling the remaining portion of the metal bar to form a main conductive core, thus obtaining the main conductive core and the conductive core of the contact pin formed from a single piece made from the first metallic material; may include:

[0043] The method comprises the following additional steps: Inserting the main conductive core into a sheath that is provided with pre-machined end pieces intended in particular to come into contact with the contact pins; - inserting the conductive core of the contact pin into a housing of the contact pin made at least partly from a second metallic material, in particular obtained by die cutting or bending; TIG (Tungsten Inert Gas) welding the sheath and the housing, in particular all around. It may further include:

[0044] In addition, the method comprises the following additional steps: drilling holes in the contact pin housing and the contact pin conductive core to form fastening passages; inserting a tube made of a second metallic material into the passage and welding the tube and the housing together by TIG welding; attaching a closure cap to the second end of the assembly; It may further include:

[0045] The manufacturing method according to the invention may include the step of applying a hot isostatic pressing (HIP) diffusion welding cycle.

[0046] The hot isostatic pressing (HIP) diffusion welding cycle has the following operating conditions: subjecting the assembly to a temperature between 600°C and 1060°C, preferably between 800°C and 1000°C, in particular to a temperature of 920°C; applying a pressure of between 500 and 1500 bar, preferably between 800 and 1200 bar, in particular 1020 bar, to the sheath; applying a pressure and temperature level for a period of 30 minutes to several hours, preferably 1 hour to 3 hours, in particular 2 hours; Cooling and depressurizing the assembly It can be performed by:

[0047] Furthermore, according to another of its aspects, the present invention also relates to the use of at least one electrical conductor as defined above as an electrical conductor of an electrochemical system, the electrochemical system comprising: an enclosure for air circulation within a volume defined by the enclosure; An electrochemical device contained within an enclosure, comprising: a stack of basic electrochemical cells of the SOEC / SOFC type solid oxide type operating at high temperature connected in series between two electrical terminals, each with an electrolyte interposed between a cathode and an anode; the at least one electrical conductor connected to at least one of the two electrical terminals; an electrochemical device comprising: Equipped with.

[0048] Furthermore, according to another aspect thereof, the present invention provides: an enclosure for air circulation within a volume defined by the enclosure; An electrochemical device contained within an enclosure, comprising: a stack of basic electrochemical cells of the SOEC / SOFC type solid oxide type operating at high temperature connected in series between two electrical terminals, each with an electrolyte interposed between a cathode and an anode; said at least one electrical conductor as defined above connected to at least one of two electrical terminals; an electrochemical device comprising: The present invention further relates to an electrochemical system comprising:

[0049] The invention can be better understood by reading the following detailed description, by reading non-exhaustive examples of implementations of the invention, and by examining the schematic and partial diagrams in the accompanying drawings. [Brief explanation of the drawings]

[0050] [Figure 1] FIG. 1 is a schematic diagram of an exemplary electrochemical cell of an electrolyzer of an HTSE. [Figure 2] FIG. 2 is a schematic diagram of a stack of cells according to FIG. 1. [Figure 3] FIG. 3 is a schematic diagram of a system incorporating the stack according to FIG. 2. [Figure 4] FIG. 1 is a schematic diagram of an electrochemical cell of a SOFC stack. [Figure 5] 1 is a schematic diagram of an electrical conductor according to the present invention; [Figure 6] FIG. 6 is a schematic cross-sectional view taken along plane VI-VI of FIG. 5. [Figure 7] 1A-1D are perspective views illustrating steps of a method for manufacturing an electrical conductor according to the present invention. [Figure 8] 1A-1D are perspective views illustrating steps of a method for manufacturing an electrical conductor according to the present invention. [Figure 9] 1A-1D are perspective views illustrating steps of a method for manufacturing an electrical conductor according to the present invention. [Figure 10] 1A-1D are perspective views illustrating steps of a method for manufacturing an electrical conductor according to the present invention. [Figure 11] 1A-1D are perspective views illustrating steps of a method for manufacturing an electrical conductor according to the present invention. [Figure 12] 1A-1D are perspective views illustrating steps of a method for manufacturing an electrical conductor according to the present invention. [Figure 13] 1A-1D are perspective views illustrating steps of a method for manufacturing an electrical conductor according to the present invention. [Figure 14] 1A-1D are perspective views illustrating steps of a method for manufacturing an electrical conductor according to the present invention. [Figure 15] 1A-1D are perspective views illustrating steps of a method for manufacturing an electrical conductor according to the present invention. [Figure 16] 1A-1D are perspective views illustrating steps of a method for manufacturing an electrical conductor according to the present invention. [Figure 17] 1A-1D are perspective views illustrating steps of a method for manufacturing an electrical conductor according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0051] In all of these figures, the same references may indicate the same or similar elements.

[0052] Furthermore, the individual parts shown in the figures are not necessarily drawn to uniform scale in order to make the figures more legible.

[0053] 1 to 4 have already been described above in relation to the prior art and the technical context of the present invention.

[0054] 5 and 6, an example of an electrical conductor 70 according to the present invention is shown.

[0055] The electrical conductor 70 includes an assembly 72 consisting of a main conductive core 74 made of a first metallic material, here copper, inserted into a sheath 79 made of a second metallic material, here a stainless steel alloy, particularly Inconel 600, having an electrical resistivity greater than that of the first metallic material to prevent oxidation of the first metallic material, which would reduce its electrical conductivity.

[0056] It should be noted that although the main conductive core 74 is here made from copper, the present invention also applies to other good conductive metals that are susceptible to oxidation, such as nickel, silver, brass, bronze, and / or copper alloys, as hardened by dispersions.

[0057] Additionally, the electrical conductor 70 comprises a contact pin 78, which comprises a protective housing 76 and a contact pin conductive core 73, advantageously made from a first metallic material and connected to the first end 72a of the assembly 72. To ensure electrical continuity over the entire length, the contact pin conductive core 73 and the main conductive core 74 are made from a single piece, in other words, they form one and the same part, here made from copper, to obtain an integrated current conductor.

[0058] The connection pin 78 hermetically closes the end 72a of the assembly 72, preventing the passage of gases, and makes it possible to create an electrical connection terminal having a shape complementary to the plate of the electrolytic cell to which the pin 78 is fixed for electrical connection of the electrolytic cell.

[0059] The shape or geometry of the connection pin 78 may be that of a regular terminal, as represented herein, or may be any other different shape, e.g., cylindrical, designed to fit into a hole or be sandwiched between two half-shells interconnected with the device to be supplied.

[0060] Furthermore, the electrical conductor 70 also includes a closure cap 80 at the second end 72b of the assembly 72. This closure cap 80 allows the assembly 72 to be vacuum-sealed at its end 72b. This closure cap 80 is made, for example, from a second metallic material, in particular a stainless steel alloy, such as Inconel 600. The end piece 80 allows the end 72b of the assembly 72 to be hermetically closed, except for a central channel 84 that passes through the assembly 72 and is designed to connect with a vacuum seal tube.

[0061] The conductive core 73 of the contact pin can advantageously be obtained by forging or die cutting, in particular from a round copper bar, for example of the CuCl type.

[0062] Forging is a technique for obtaining mechanical parts by applying a large force to a metal rod, either cold or hot, to force it to conform to a desired shape. Forging involves a striking device, such as a hammer, sledgehammer, jack, or tapping hammer, and a support, such as an anvil or die. Forging does not allow the same tolerances as machining and is limited to parts that require high strength but low precision, such as bolts or tools. The deformation of the metal causes a number of metallurgical phenomena, both at the microscopic and macroscopic levels, making the resulting parts more resistant to mechanical stresses. Among these phenomena, the most prominent is waviness, which is itself a cause of metal fiberization.

[0063] Die cutting or die forging consists of heating a blank made from an alloy such as aluminum, copper, titanium, or nickel alloy, and then shaping it by plastic deformation. Die cutting of steel is called "stamping." Die cutting is a forging operation performed using a tool called a die, typically an upper die half and a lower die half. The die transfers the shape of the part to the impression.

[0064] 7 to 17 make it possible to show in perspective views the steps of the method for manufacturing an electrical conductor 70 according to the invention.

[0065] 7 thus shows a metal bar 90, for example of cylindrical shape and of circular cross section, made of a first metallic material, here with a diameter of 14 mm. In particular, the metal bar 90 is a round piece of copper of the CuCl type. This metal bar 90 is designed to form the conductive core 73 and the main conductive core 74 of a contact pin made from a single piece.

[0066] The volume of the conductive core 73 of the contact pin, which is produced starting from this metal bar 90 by forging or, as in this case, by die cutting, depends on the volume of the bar 90 used. A typical volume, i.e., about 6400 mm² for a cross section of 160 mm², is 3 To obtain this, the diameter of the rod 90 is 160 mm. 2, i.e., a diameter of about 14 mm.

[0067] After a die-cutting operation on the metal bar 90, the conductive core 73 of the contact pin is obtained, here in the shape of a square hexahedron, at the end of the metal bar 90.

[0068] The subsequent operation, shown in Figure 9, consists in rolling the remaining part of the metal rod 90 to the desired diameter to obtain the main conductive core 74. The 14 mm diameter is then changed to 10 mm to allow its insertion into the sheath 79, in particular in the form of an Inconel 600 tube with a diameter of 10 / 12. A clearance of between 4 / 10 and 6 / 10 is required between the inner diameter of the sheath 79 and the outer diameter of the main conductive core 74 obtained by rolling.

[0069] Rolling is a plastic deformation manufacturing process. It concerns various materials, such as metals or any other material in paste form, such as paper or food pulp. This deformation is obtained in particular by successive compression as it passes between two counter-rotating cylinders called "rollers."

[0070] Thus, at this stage, shown in FIG. 9, an integral part is obtained comprising a main conductive core 74 and a conductive core 73 of the contact pin, both made of copper.

[0071] In the next step shown in Figure 10, a sheath 79, here made from Inconel 600, having a diameter of 12 / 10 mm is inserted around the main conductive core 74 and the part formed from the conductive core 73 of the contact pin.

[0072] The end piece 77 of the sheath 79, shown enlarged in Figure 11, has been pre-machined to obtain a shape designed to fit the heel of the conductive core 73 of the contact pin. This end piece 77 may have, for example, a parallelepiped shape, as can be seen in Figure 11, but any other shape is also possible.

[0073] 12, a prefabricated housing 76 of the contact pin, here made from Inconel 600, the thickness of which is for example between 0.5 mm and 1 mm, then covers the conductive core 73 of the contact pin. This housing 76 is therefore closed at one end and open at the other opposite end to allow the insertion of the conductive core 73 of the contact pin.

[0074] The housing 76 can be obtained by die cutting or bending, and advantageously its thickness is as thin as possible while still allowing welding, in order to present as little resistance as possible to the current.

[0075] Punching is a manufacturing technique for obtaining objects that cannot be developed from flat, thin sheet metal, and may be considered for mass production of such housings 76.

[0076] At the first end 72a of the assembly 72 thus formed, the sheath 79 and the housing 76 are then welded together by a full-circumference TIG weld, for example an orbital weld, represented by S in Fig. 13, with the addition of a material preferably made of a second metallic material. In this way, the housing 76 is connected to the sheath 79 by means of the full-circumference TIG weld, to make the joint gas-tight.

[0077] Holes or bores are then made in the conductive core 73 and housing 76 of the contact pin, as seen in FIG. 14, to create passages 91 for bolts that allow current conductors to be connected to the contact pins of the stack.

[0078] 15, the passage 91 thus formed is then covered using a tube 92, here made of stainless steel, in particular Inconel 600, inserted into the passage 91, in the same logic of protecting the copper against oxidation. This tube 92 is then TIG welded on two sides to the housing 76 around it, as shown diagrammatically by the reference S in FIG. 16. The inner diameter of this tube 92 must allow the passage of the connecting bolt between the current conductor and the stack connecting pin.

[0079] Finally, as shown in FIG. 17, a closure cap 80 is welded to the second end 72b of the assembly 72 to secure the electrical conductor 70. It is therefore possible to vacuum-seal the assembly 72 through a tube added for this purpose. A degassing tube is then added to the end 72b, and the sheath 79 is evacuated by pumping through the tube. A tube processing can then be performed to permanently maintain the vacuum, allowing the tube to be airtight and permanently sealed. Such a vacuum step can also allow for leak testing. The rod is then subjected to a HIP (hot isostatic pressing) cycle, as described in patent application FR3036840A1.

[0080] The stainless steel alloys of the sheath 79, housing 76, tube 92, and closure cap 80 are selected depending on the thermal stresses to which the electrical conductor 70 will be subjected. In particular, they can be made of Inconel 600 for temperatures up to 900°C. Additionally, the cross sections of these elements can be selected depending on requirements, such as current, voltage drop, etc.

[0081] A method for manufacturing such an electrical conductor 70 designed to be used as an electrical conductor for supplying power to an electrochemical system, such as the electrochemical systems of FIGS. 1 to 4, may, for example, comprise the following steps: Manufacturing the components (core, sheath, pin) described above; cleaning the parts, in particular the surfaces intended to be welded, i.e. the electrically conductive surfaces and the surfaces necessary to seal the electrical conductors, with detergents and / or solvents or any other means; X-ray inspection of welds to check the quality of the welds from the mechanical, electrical and sealing standpoints. may further include one or more of:

[0082] By comparing in Table 1 below the resistance values ​​obtained for a main conductive core 74 made of copper with a diameter of 14 mm at 1 m, the resistance values ​​of a reference whistle 78 (prior art embodiment) made of Inconel 600 and the resistance values ​​of a whistle 78 according to the invention (conductive core 73 and housing 76 of the contact pin), it can be observed that at 800°C the resistance value of the reference whistle 78 represents about one third of the total current conductor in the case of a main conductive core of only 1 m. Switching to the conductive core 73+housing 76 version of the whistle 78 makes it possible to reduce the resistance value by a factor of 12 at 800°C and by a factor of 41 at ambient temperature (20°C).

[0083] [Table 1]

[0084] Regarding the results in Table 1, the resistivity of copper is 17.24.10 at cold temperature (20°C). -9 Ω·m, 70.10 at 800℃ -9 The resistivity of Inconel 600 is 1.03.10 Ω·m when cold (20°C). -6 Ω·m, 1.13.10 at 800°C -6 Ω·m.

[0085] The electrical conductor 70 obtained according to the principles of the present invention is therefore an electrical conductor suitable for the high temperatures and high currents of stacks of SOEC / SOFC solid oxide cells, which advantageously makes it possible to limit electrical losses at the level of the contact pin 78 by avoiding any interruption of the electrical continuity between the main conductive core 74 and the conductive core 73 of the contact pin.

[0086] The present invention may be applied to high temperature steam electrolysers, high temperature co-electrolysers fed with a mixture of water vapor (HO) and carbon dioxide gas (CO), high temperature solid oxide fuel cells, reversible systems, high temperature fuel cells and electrolysers, "intermediate temperature" i.e. 400°C cells or electrolysers, or PCFCs (protonic ceramic fuel cells), as explained above.

[0087] The invention applies to the above systems operating at atmospheric pressure, but also to pressurized systems.

[0088] Besides the technical field of solid oxide electrochemical systems, the invention applies to all fields where electrical conduction is required in high temperature oxidizing environments or under conditions that lead to rapid degradation of conductive materials.

[0089] Of course, the invention is not limited to the exemplary embodiments just described, as various modifications can be made thereto by those skilled in the art. [Explanation of symbols]

[0090] 10 Solid oxide cells, cells, basic electrochemical cells 12 First porous conductive electrode, cathode 14 Second porous conductive electrode, anode 16 Solid oxide (high density electrolyte) membrane, membrane, electrolyte 18 Interconnection Plate, Plate 20 stack, HTSE electrolyzer, electrolyzer 22 Water vapor source 24 valves 26 Gas manifold 28 Power supply, current source 30 Terminals, electrical terminals 32 Terminals, electrical terminals 52 Pipe 54 Pipe 56 Pipe 58 Pipe 60 Enclosure 62 Air inlet duct, duct 64 Air outlet duct, outlet duct 66 Electrical conductors, conductors 68 Electrical conductors, conductors 70 Electrical Conductors 72 Assembly 72a first end, end 72b second end, end 73 Conductive Core 74 Main conductive core 76 Protective housing 77 End Piece 78 connecting pins 79 Sheath 80 Closure cap, end piece 84 Center Channel 90 Metal rods, rods Aisle 91 92 tubes

Claims

1. an assembly (72) comprising a main conductive core (74) made of a first metallic material and a sheath (79) covering the main conductive core (74) and made of a second metallic material having an electrical resistivity greater than the electrical resistivity of the first metallic material; a contact pin (78) connected to the first end (72a) of the assembly (72), the contact pin (78) comprising a conductive core (73) of the contact pin and a protective housing (76) of the contact pin; An electrical conductor (70) comprising: An electrical conductor (70) characterized in that the connection pin (78) is at least partially made from the second metallic material, in particular the protective housing (76) is made from the second metallic material, the conductive core (73) of the connection pin is made in particular from the first metallic material, and the conductive core (73) and the main conductive core (74) of the connection pin are made from a single part.

2. a closure cap (80) made at least in part from said second metallic material and connected to the second end (72b) of said assembly (72), said closure cap (80) comprising, in particular, a central channel (84); The conductor of claim 1 , comprising:

3. 3. The conductor according to claim 1 or 2, characterized in that the sheath (79) comprises an end piece (77) which contacts the contact pin (78) at the first end (72a) of the assembly (72).

4. 4. The conductor according to claim 1, wherein the conductive core (73) of the contact pin is inserted into the housing (76) of the contact pin, which is at least partially made from the second metallic material.

5. 5. The conductor according to claim 4, characterized in that the housing (76) and the conductive core (73) of the contact pin are drilled to form a passage (91) for accommodating a tube (92) at least partially made of the second metallic material.

6. 6. The conductor according to claim 1, wherein the main conductive core (74) and the contact pins (78) are made from copper, nickel, or silver, and / or alloys of copper, nickel, or silver.

7. 7. The conductor according to any one of claims 1 to 6, characterized in that the sheath (79) is made from a stainless or refractory metal and / or a metal or refractory alloy, in particular a stainless or refractory steel.

8. A method for manufacturing an electrical conductor (70) according to any one of claims 1 to 7, comprising the steps of: A method characterized in that it includes the step of manufacturing the conductive core (73) of the contact pin by forging or die cutting.

9. The following steps: forging or die-cutting the end of a metal rod (90), in particular of cylindrical shape and circular cross section, made from said first metallic material, to form said conductive core (73) of said contact pin; rolling the remaining portion of said metal bar (90) to form said main conductive core (74), thus obtaining said main conductive core (74) and said contact pin (78) formed from a single piece made from said first metallic material; 9. The method of claim 8, comprising:

10. The following additional steps: Inserting said main conductive core (74) into said sheath (79) which is provided with a pre-machined end piece (77) specifically designed to contact said contact pin (78); inserting the conductive core (73) of the contact pin into the housing (76) of the contact pin made at least partly from the second metallic material, in particular obtained by die cutting or bending; TIG welding the sheath (79) and the housing (76); 10. The method of claim 9, comprising:

11. The following additional steps: Drilling holes in the housing (76) of the contact pin and in the conductive core (73) of the contact pin to obtain fastening passages (91); inserting a tube (92) made of the second metallic material into the passage (91) and TIG welding the tube (92) to the housing (76); attaching a closure cap (80) to the second end (72b) of the assembly (72); The method of claim 10, comprising:

12. 12. A method according to any one of claims 8 to 11, characterized in that it comprises the step of applying a diffusion welding cycle by hot isostatic pressing (HIP).

13. The hot isostatic pressing (HIP) diffusion welding cycle is performed under the following operating conditions: subjecting the assembly (72) to a temperature between 600°C and 1060°C, preferably between 800°C and 1000°C, in particular a temperature of 920°C; - applying a pressure of between 500 and 1500 bar, preferably between 800 and 1200 bar, in particular a pressure of 1020 bar, to said sheath (79); applying pressure and temperature levels for a period of 30 minutes to several hours, preferably 1 hour to 3 hours, in particular 2 hours; cooling and depressurizing the assembly; 13. The method of claim 12, wherein the method is performed by:

14. Use of at least one electrical conductor (70) according to any one of claims 1 to 7 as an electrical conductor in an electrochemical system, said electrochemical system comprising: an enclosure (60) for circulating air within a volume delimited by said enclosure (60); An electrochemical device housed within the enclosure (60), a stack (20) of elementary electrochemical cells (10) each having an electrolyte (16) interposed between a cathode (12) and an anode (14), connected in series between two electrical terminals (30, 32) and having a solid oxide SOEC / SOFC type operating at high temperature; the at least one electrical conductor (70) connected to at least one of the two electrical terminals (30, 32); an electrochemical device comprising: To have, to use.

15. an enclosure (60) for circulating air within a volume delimited by said enclosure (60); An electrochemical device housed within the enclosure (60), a stack (20) of elementary electrochemical cells (10) each having an electrolyte (16) interposed between a cathode (12) and an anode (14), connected in series between two electrical terminals (30, 32) and having a solid oxide SOEC / SOFC type operating at high temperature; At least one electrical conductor (70) according to any one of claims 1 to 7 connected to at least one of the two electrical terminals (30, 32); an electrochemical device comprising: An electrochemical system comprising:

Images