GAS PIPING DEVICE FOR HIGH-TEMPERATURE FUEL CELLS

Description

[0001] The present invention relates to a gas conduit device for conveying a high-temperature gas between at least two fuel cell stacks, as well as a gas conduit arrangement and a high-temperature fuel cell system comprising the same.

[0002] The gas piping device according to the invention is used in plant construction for renewable energy generation with solid oxide fuel cells (SOFCs) or hydrogen production with solid oxide electrolytes (SOECs), which are operated at high temperatures between 500 °C and 1000 °C. The high operating temperatures and temperature fluctuations during shutdown and restart in the event of a plant standstill therefore place special demands on the plant technology.

[0003] A system technology for a solid oxide fuel cell (SOFC) system is known in which the fuel cell stacks are isolated from the system's peripheral equipment by an electrically insulating coating on the stack components or a surrounding housing. Due to technical limitations of the coating technology and / or the layer thickness, the maximum achievable insulation performance of this design is also limited.

[0004] In a conventional SOFC system configuration, the fuel cell stacks are typically connected electrically in series and operated together. Although the insulating properties of an insulating coating are limited, they are usually sufficient in such a conventional system configuration with series-connected fuel cell stacks, as they only need to withstand the maximum potential difference between the stack ends or the output voltage of a fuel cell stack.

[0005] Gas conduit devices for conveying a high-temperature gas between at least two fuel cell stacks are known, for example, from US 2014 / 147766 A1 and US 2015 / 357669 A1.

[0006] It is an object of the invention to provide a suitable technology for the construction of plants for high-temperature fuel cells, which provides improved or alternative electrical insulation in an arrangement of fuel cell stacks, in particular with regard to a connecting plant technology between the individual fuel cell stacks of the arrangement.

[0007] A further object of the invention is to create a suitable technology for the construction of plants for high-temperature fuel cells with regard to a connecting plant technology between individual fuel cell stacks of a system, which enables an alternative electrical interconnection and / or an alternative electrically interconnected arrangement of the fuel cell stacks.

[0008] The aforementioned problems are solved by a gas piping device with the features of claim 1. Further technical solutions based on this are based on a gas piping arrangement or a high-temperature fuel cell system according to claims 10 or 12, which include the features of the gas piping device and benefit from its advantages. Further features and details of the invention will become apparent from the dependent claims, the description, and the drawings.

[0009] The gas conduit device according to the invention serves to convey a high-temperature gas from high-temperature fuel cells and has a conduit body and a passage channel extending through the conduit body to guide a flow of the high-temperature gas along an axial direction.

[0010] According to the invention, the conductor body is made of a ceramic material, for electrical insulation of electrical potentials at axial ends of the conductor body.

[0011] The invention thus provides for the first time an electrically insulating body as an intermediate piece in a high-temperature resistant gas line for fuel cells or electrolyzers with high operating temperature, such as in particular in a SOFC system or SOEC system.

[0012] To take into account the high operating temperatures of the gases, the invention further provides for the first time a ceramic body as an intermediate piece in a gas line, which is usually made predominantly of high-temperature resistant steels.

[0013] An advantage of the invention is that the high-temperature-resistant ceramic conductor body of the gas piping device according to the invention effectively interrupts electrical conductivity along a gas piping section, which is based on the electrical conductivity of metallic materials in piping sections. This prevents possible short-circuit currents or parasitic currents via pipelines between fuel cells in any arrangement and configuration.

[0014] Since the insulation of the ceramic conductor body of the gas piping device according to the invention is arranged in a periphery of a system technology for media guidance that is predominantly made of steel, a further advantage of the invention is the now fundamental possibility of a serial connection of high-temperature fuel cell stacks that need to be supplied with gas flows.

[0015] As a further advantage of the invention, the material thickness of the ceramic conductor body of the gas piping device according to the invention results in a significantly higher insulation property compared to a conventional insulating coating of an environment or outer surface of a fuel cell stack.

[0016] According to an advantageous aspect of the invention, the ceramic material from which the conductor body is made can be a metallizable aluminum oxide, wherein the conductor body preferably has metallization on axially separated surface sections, as a basis for a metallurgical connection technique. Thus, despite the ceramic material, an effective connection to a metallic component is enabled by means of brazing. Since the metallized surfaces are separated, there is no axial conductivity via the metallization of the conductor body. The ceramic material from which the conductor body is made is particularly preferably Al₂O₃.

[0017] According to an advantageous aspect of the invention, the gas piping device can have connection sections arranged towards the axial ends of the pipe body, with a pipe connection surface that encloses the passageway towards the axial ends of the gas piping device. This provides an improved connection to a pipe body of an adjacent pipe section.

[0018] According to an advantageous aspect of the invention, the connecting sections can be made of a metallic material, in particular a high-temperature-resistant steel, preferably an austenitic chromium-nickel steel alloy, which in particular has a high temperature resistance of more than 1000 °C, preferably up to 1100 °C, or can be made of Ni200. The connecting sections, which are preferably made of Ni200, are preferably directly connected to the conductor body. The conductor body is in particular made of Al₂O₃. These two materials (Ni200 and Al₂O₃) have a similar coefficient of thermal expansion, so that no further connecting element appears to be necessary.

[0019] According to the invention, the gas piping device further comprises connecting means which, on the one hand, are connected to the piping body via an extension axially overlapping with the piping body, and on the other hand, are connected to the connection section via an extension axially overlapping with one of the connection sections, for fastening and / or sealing between the piping body and the connection sections. The axial overlaps enable compensation between the different thermal expansions of a ceramic of the piping body and different metals of the connecting means and the connection sections.

[0020] The design stipulates that the connecting elements and the connection sections are made of the same metallic material, preferably Ni200. Ni200 is an unalloyed nickel with a nickel content of at least 99.2%, which is why Ni200 is a pure metal and not an alloy. If the connection sections and the connecting elements are made of the same material, they consequently form a single, common element. According to the invention, this can advantageously be interpreted as eliminating the need for a connecting element; the connection sections are sufficient and are then preferably directly connected to the conductor body. The conductor body is, in particular, made of Al₂O₃. This design of the connecting element and the conductor body further reduces the disadvantages of thermal expansion.

[0021] According to an advantageous aspect of the invention, the connecting elements can be made of a metallic material, preferably a nickel-iron-cobalt alloy with a low coefficient of thermal expansion of less than 7.0 x 10⁻⁶ < 1 / K, or of Ni200. The low thermal expansion of the nickel-iron-cobalt alloy offers the advantage of minimizing material stresses at a connection point between a ceramic material and the components due to differing thermal expansions. If, in contrast, the connecting elements are made of Ni200, they can be formed in one piece with the connecting sections, which are also made of Ni200.

[0022] According to an advantageous aspect of the invention, the connecting element can be ring-shaped and enclose one circumference of the conductor body and / or one circumference of one of the connection sections, for a radial force-fit and / or form-fit connection between the connecting element and the conductor body and / or between the connecting element and the connection sections. Thus, the connecting element achieves a mechanical fastening at the component boundaries.

[0023] According to an advantageous aspect of the invention, the conductor body can comprise a metallization incorporated into the ceramic material on circumferential surface sections, and the connecting element and / or the connection section can be connected to the metallized circumferential surface by a soldering agent, thus creating a metallurgical bond between the connecting element and / or the connection section and the conductor body. In addition to providing extra fastening, the connecting element also improves the sealing of the gas piping device under the operating pressures present. The soldering agent is preferably made of gold to prevent corrosion. If the connecting element and the connection section are made of the same material and thus formed as a single piece, both are consequently connected to the metallic circumferential surface by the soldering agent, which is preferably made of gold.

[0024] Since the gas piping device is the smallest manageable and tradable unit of the invention, and therefore subject to protection, a gas piping arrangement and a system structure described later represent further technical aspects of the invention that benefit from the advantages of the gas piping device explained above.

[0025] According to a further aspect of the invention, a gas line arrangement for conveying a high-temperature gas from high-temperature fuel cells can be equipped with at least one gas line device according to the invention. Furthermore, the gas line arrangement has tubular sections for axially guiding a flow of gas along the gas line arrangement; wherein the at least one gas line device is arranged between two of the line sections to interrupt electrical conductivity along the gas line arrangement.

[0026] According to an advantageous aspect of the invention, the gas piping arrangement can include compensation sections with a tubular outer body having an axially flexible contour, for compensating axially acting forces and / or angular misalignments in the gas piping arrangement resulting from different thermal expansions of the piping sections and the gas piping device. This extends the service life of the gas piping device, in particular the ceramic piping body.

[0027] According to a further aspect of the invention, a high-temperature fuel cell system can comprise several fuel cell stacks and at least one gas line arrangement for conveying an anode supply gas and / or an anode discharge gas, as well as at least one gas line device according to the invention. The gas line arrangement between at least two of the fuel cell stacks comprises the at least one gas line device.

[0028] According to an advantageous aspect of the invention, the at least one gas line arrangement can connect branches for a parallel supply or discharge of the high-temperature gas to the fuel cell stacks; and the gas line arrangement can have the gas line device between each of the branches.

[0029] According to an advantageous aspect of the invention, at least two of the fuel cell stacks can be arranged one above the other in a stacking direction of the fuel cells, and the at least one gas line arrangement can pass by the fuel cell stacks substantially parallel to the stacking direction.

[0030] According to an advantageous aspect of the invention, several of the fuel cell stacks can be stacked one above the other in a stacking direction of the fuel cells in the form of a tower, and the ends of the fuel cell stacks can be electrically connected to each other in series; wherein in the at least one gas line arrangement, one of the gas line devices is arranged between each branch of the gas line arrangement to one of the fuel cell stacks, for isolating the gas line arrangement between different potentials of the serially connected, stacked fuel cell stacks along the stacking direction.

[0031] According to an advantageous aspect of the invention, the branches for a parallel supply or discharge of the high-temperature gas at the fuel cell stacks can be integrated into the end plates of the fuel cell stacks; wherein the end plates extend through a cross-section of the at least one gas line arrangement, for a connection of the integrally formed branches to the gas line arrangement. This results in a space-saving design of the fuel cell stacks and their lines, which allows for a denser arrangement of several such towers of fuel cell stacks within the area of ​​a SOFC system.

[0032] Further advantages, features, and details of the invention will become apparent from the following description, in which an exemplary embodiment is described in detail with reference to the drawing. The drawing schematically shows: Fig. 1 shows a perspective view of an embodiment of the gas piping device; Fig. 2 shows an axial longitudinal section through the same embodiment of the gas piping device; and Fig. 3 shows a view of a high-temperature fuel cell system with an enlarged view of a gas piping arrangement in which the gas piping device is used as a component.

[0033] Fig. 1 Figure 1 shows an embodiment of the gas piping device 10 comprising several components, wherein the perspective view shows the gas piping device 10 in a composite state in the sense of an assembly according to the embodiment.

[0034] As in Fig. 2 As shown in a longitudinal section through the gas piping device 10, the underlying assembly of the illustrated embodiment comprises, in detail, a cylindrical piping body 11 with a cylindrical through-channel 15 formed therein, as well as two adjacent flange-shaped connection sections 12 and two annular connecting elements 13 that encompass the piping body 11 and the connection sections 12. According to the invention, the connection sections 12 and the connecting elements 13 can also advantageously be formed as a common element made of the same material. In this case, the through-channel 15 borders the common element consisting of the connection sections 12 and the connecting elements 13. It is also advantageous if the connecting element 13 is omitted and the connection sections are formed from Ni200.

[0035] The conduit body 11, as part of a possible embodiment of the gas conduit device 10 reduced to a minimal number of components, represents a key component. The conduit body 11 is preferably designed in a rotationally symmetrical shape with a constant inner diameter for the through-channel 15. An outer surface is preferably stepped to form two separate circumferential surface sections 16 at the axial ends of the conduit body 11, which serve to receive and as contact surfaces for the annular connecting elements 13. Since the conduit body 11 is made of a ceramic material, it is practically non-conductive and provides insulation between adjacent sections of a gas conduit.

[0036] The ceramic material is an aluminum oxide with the standard designation AK97M, which, in addition to high electrical resistance, is also characterized by good metallizability, thus enabling the production of a hard-soldered connection to other components made of a metallic material in the metallized state of a surface.

[0037] Based on this property, a metallization at a predetermined surface depth is introduced into the aluminum oxide on the circumferential surface sections 16 of the conductor body 11. Since an axially central part of the conductor body 11 has no metallization, the axial insulation property is maintained.

[0038] The connecting sections 12 abut a flange-shaped end face of an end face of the axial ends of the conduit body 11. An inner diameter of the preferably rotationally symmetrical connecting sections 12 corresponds to the through-channel 15 for its homogeneous continuation. A stepped outer surface has a connection surface 14 with a reduced diameter axially outward. This optional shape allows, for example, a push-fit or press fit of the connection surface 14 in conjunction with an adjacent conduit pipe. On an axially opposite side, a portion of the stepped outer surface with a larger radius, at least section by section up to an axial stop, has the same circumference as the adjacent circumferential surface sections 16 of the conduit body 11, for receiving and as a contact surface for the annular connecting elements 13.

[0039] The metallic material of connection section 12 is an austenitic chromium-nickel steel alloy with the standard designation X15CrNiSi25-21 or material number 1.4841. This alloy is characterized by its corrosion resistance and temperature resistance up to approximately 1,150 °C and is therefore particularly suitable for the construction of a SOFC system. Preferably, other components of the gas piping assembly, such as the pipe sections and the expansion joints, are also made of the same steel alloy.

[0040] The metallic material of the connecting element 13 is a nickel-iron-cobalt alloy with the standard designation NiCo29-18 or the material number 1.3981. The alloy is characterized by a very low coefficient of thermal expansion of approximately 5.0 - 6.5 x 10 - 6 < 1 / K, depending on the temperature range, which allows a good approximation to the low coefficient of expansion of the ceramic and, if applicable, metallized material of the conductor body 11.

[0041] In the described embodiment, the gas piping assembly 10 not only has a force-fit or form-fit connection between the connecting element 13, the pipe body 11, and the connection sections 12, but also a material-bonded connection. A metallization is introduced into the ceramic or aluminum oxide on one surface of the circumferential sections 16 of the pipe body 11. A brazed connection made of hard solder is applied between the metallized circumferential sections 16 and the annular connecting elements 13 made of the metal alloy for additional fastening and sealing (not shown). A brazed or welded connection is also applied between the annular connecting elements 13 made of the metal alloy and the connection sections 12 made of the steel alloy for additional fastening and sealing (not shown).

[0042] Thus, in the described embodiment, the connecting means 13 provide both a mechanical fastening and a seal between the conductor body 11 and the connection sections 12. In In alternative embodiments, the connecting means 13 can also fulfill only one of the two properties, while the other property is fulfilled by additional fastening means or sealing means.

[0043] Fig. 3 Figure 1 shows a representation of a SOFC system, i.e., a high-temperature fuel cell system 30, in which the fuel cell stacks 31, as well as the fuel cells within the fuel cell stacks 31, are stacked one above the other in the same stacking direction in the form of a tower and are electrically connected to each other in series. Two gas line arrangements 20 run parallel to the stacking direction past the fuel cell stacks 31.

[0044] One of the two gas line arrangements 20 supplies an anode supply gas preheated to high temperatures to all fuel cell stacks 31 in parallel. The other of the two gas line arrangements 20 supplies an anode discharge gas with a high reaction temperature to all fuel cell stacks 31 in parallel. Each fuel cell stack 31 has an end plate 32 designed as a media distribution plate, in which channels branching off the anode supply gas from one gas line arrangement 20 and channels branching off the anode discharge gas into the other gas line arrangement 20 are integrally formed. The end plates 32 extend into the cross-section of the gas line arrangements 20 to establish a branching connection from an internal channel of the end plates 32 to the gas flow in the gas line arrangements 20.Due to the metallic materials of the end plates 32 of the fuel cell stacks 31 and the components of the gas line assembly 20, a short-circuit current would propagate through the gas line assemblies 20 in the described embodiment of the system without electrical insulation, due to the different potentials of the series-connected fuel cell stacks 31 along the entire stacking direction of the tower-shaped arrangement. However, due to a plurality of electrically insulating gas line devices 10 arranged along the gas line assemblies 20 between each branch of the gas flow to each fuel cell stack 31, i.e., between each interface with a media-carrying end plate 32, complete electrical isolation of the periphery between the series-connected fuel cell stacks 31 is achieved.

[0045] As on a left side of the Fig. 3As shown, the gas line arrangement 20, in combination with the gas line devices 10, preferably comprises further components. In addition to line sections 22, which form an adjacent line path to the gas line devices 10 and the media-carrying end plates 32, compensation sections 21 are also arranged between them. The compensation sections 21 have an axially flexible outer surface, for example in the form of a bellows, and compensate for forces arising from material stresses due to differing thermal expansion behavior of the component materials. Thus, the compensation sections 21 prevent, in particular, the ceramic material of the line section 11, which has a comparatively brittle material property, from being exposed to harmful axial forces and / or angular misalignments resulting from the expansion of the line sections 22 made of a steel alloy with a significantly higher thermal expansion. Reference symbol list

[0046] 10 Gas piping device 11 Piping body 12 Connection section 13 Connecting element 14 Connection surface 15 Through channel 16 Metallized circumferential surface section 20 Gas piping arrangement 21 Compensation section 22 Piping section 30 High-temperature fuel cell system 31 Fuel cell stack 32 End plate of fuel cell stack

Claims

1. Gas conduit apparatus (10) for conducting a high-temperature gas from high-temperature fuel cells, comprising: a conduit body (11) and a passageway (15) extending through the conduit body (11) for conducting a flow of the high-temperature gas along an axial direction, wherein the conduit body (11) is made of a ceramic material, for electrical insulation of electrical potentials at axial ends of the conduit body (11), wherein further connecting means (13) are provided, each of which is connected to the conduit body (11) via an extension axially intersecting the conduit body (11) and, on the other hand, is connected to the connection section (12) via an extension axially intersecting one of the connection sections (12), for fastening and / or sealing between the conduit body (11) and the connecting sections (12), characterized in that the connecting means (13) and the connecting sections (12) are made of the same metallic material.

2. Gas conduit apparatus (10) according to claim 1, wherein the ceramic material from which the conduit body (11) is made is a metallizable aluminum oxide.

3. Gas conduit apparatus (10) according to claim 2, wherein the conduit body (11) has a metallization on axially separated surface sections as a basis for a material-to-material connection technique.

4. Gas conduit apparatus (10) according to one of claims 1 to 3, further comprising connecting sections (12) arranged at the axial ends of the conduit body (11), with a connecting surface (14) enclosing the passageway (15) toward the axial ends of the gas conduit apparatus (10).

5. Gas conduit apparatus (10) according to claim 4, wherein the connecting sections (12) are made of a metallic material, preferably of an austenitic chromium-nickel steel alloy, which in particular has a high temperature resistance of more than 1000°C, preferably up to 1100°C, or of Ni200.

6. Gas conduit apparatus (10) according to one of claims 1 to 5, wherein the connecting means (13) and the connecting sections (12) are made of Ni200.

7. Gas conduit apparatus (10) according to one of claims 1 to 6, wherein the connecting means (13) are made of a metallic material, preferably of a nickel-iron-cobalt alloy, with a low expansion coefficient of less than 7.0 x 10'6 1 / K or of Ni200.

8. Gas conduit apparatus (10) according to one of claims 5 to 7, wherein the connecting means (13) are annular and each encloses a circumference of the conduit body (11) and / or a circumference of one of the connecting sections (12), for a radial force-locking and / or form-locking connection between the connecting means (13) and the conduit body (11) and / or between the connecting means (13) and the connecting sections (12).

9. Gas conduit apparatus (10) according to one of claims 1 to 8, wherein the conduit body (11) comprises a metallization introduced into the ceramic material on peripheral surface sections (16), and the connecting means (13) and / or the connecting section (12) is connected to the metallized peripheral surface (16) by a solder, for a material connection between the connecting means (13) and / or the connecting section (12) and the conduit body (11).

10. Gas conduit assembly (20) for conducting a high-temperature gas from high-temperature fuel cells, comprising at least one gas conduit apparatus (10) according to one of claims 1 to 9, further comprising: tubular line sections (22) for axially conducting a flow of the gas along the gas conduit assembly (20); wherein the at least one gas conduit apparatus (10) is arranged between two of the line sections (22) for interrupting electrical conductivity along the gas conduit assembly (20).

11. Gas conduit assembly (20) according to claim 10, further comprising compensation sections (21) with a tubular jacket body having an axially flexible contour for compensating axially acting forces in the gas conduit assembly (20) due to different thermal expansions of the line sections (22) and the gas conduit assembly (21).

12. A high-temperature fuel cell system (30) comprising a plurality of fuel cell stacks (31), which comprises at least one gas conduit assembly (20) for conducting an anode supply gas and / or an anode exhaust gas of a high-temperature gas, and at least one gas conduit apparatus (10) according to one of claims 1 to 9, wherein the at least one gas conduit assembly (20) comprises the at least one gas conduit apparatus (10) between at least two of the fuel cell stacks (31).

13. The high-temperature fuel cell system (30) according to claim 12, wherein the at least one gas conduit assembly (20) connects branches for parallel supply or discharge of the high-temperature gas to the fuel cell stacks (31); and the gas conduit assembly (20) comprises the gas conduit apparatus (10) between each of the branches.

14. The high-temperature fuel cell system (30) according to claim 12 or 13, wherein at least two of the fuel cell stacks (31) are arranged one above the other in a stacking direction of the fuel cells, and the at least one gas conduit assembly (20) extends past the fuel cell stacks (31) substantially parallel to the stacking direction.

15. The high-temperature fuel cell system (30) according to any one of claims 12 to 14, wherein a plurality of fuel cell stacks (31) are stacked one above the other in the form of a tower in a stacking direction of the fuel cells, and the ends of the fuel cell stacks (31) are electrically connected to one another in series; and in the at least one gas conduit assembly (20), between each branch of the gas conduit assembly (20) to one of the fuel cell stacks (31), one of the gas conduit apparatus (10) is arranged for isolating the gas conduit assembly (20) between different potentials of the serially connected, stacked fuel cell stacks (31) along the stacking direction.