Sealing device for at least one fuel cell stack

Abstract

The invention relates to a sealing device (1) for at least one fuel cell stack (2), in particular a SOFC stack, comprising a housing (3) and at least one fuel cell stack (2) which is or can be located within the housing (3), wherein: the at least one fuel cell stack (2) comprises a plurality of fuel cells (4); the fuel cells (4) at least each have a further seal (5) at the lateral ends thereof; the housing (3) surrounds the at least one fuel cell stack (3) with the further seal (5); at least one sealing element (6) is located between the housing (3) and the further seal (5) for pressure compensation. The invention also relates to a fuel cell system, in particular a SOFC system, having such a sealing device (1).

Description

[0001] Sealing device for at least one fuel cell stack

[0002] The invention relates to a sealing device for at least one fuel cell stack, in particular an SOFC fuel cell stack, comprising a housing and at least one fuel cell stack arranged or arrangeable within the housing, wherein the at least one fuel cell stack comprises a plurality of fuel cells, wherein the fuel cells have at least one further seal at their lateral ends, wherein the housing surrounds the at least one fuel cell stack with the further seal.

[0003] It is known from the prior art that individual fuel cell elements (anode, cathode, bipolar plate) must be sealed internally within the fuel cell stack. This is achieved with an additional seal, which is usually made of glass. However, it is quite possible that during operation of SOFC fuel cell systems, in particular, this glass seal may begin to melt or liquefy due to the high temperatures within a fuel cell stack. If the pressure differences between the fuel cell stack and the environment are too great, the glass seal may be forced outwards. This should be avoided at all costs, as it could damage or even destroy the fuel cell stack.

[0004] This is where the invention comes in. The object of the invention is to provide a sealing device that solves the problems mentioned above, in particular reducing pressure differences.

[0005] A further aim is to specify a use of such a fuel cell system.

[0006] The object is achieved according to the invention in that, in a sealing device of the type mentioned at the outset, at least one sealing element for pressure equalization is arranged between the housing and the further seal.

[0007] One advantage achieved by the inventive design of the sealing device is that the housing is no longer directly connected to the additional seal, but rather the sealing element is arranged between the housing and the additional seal. The sealing element can therefore be considered a buffer device and / or pressure compensation element.

[0008] The sealing device comprises at least one, preferably several, for example forty fuel cell stacks, wherein the housing is preferably arranged around all fuel cell stacks, i.e. a common housing is designed and provided for all fuel cell stacks. The housing seals the fuel cell stacks against the environment outside the fuel cell stacks in a gas-tight manner, although generally not pressure-tight. In sealing devices and / or fuel cell stacks according to the prior art, the ambient pressure then acts on the fuel cell stack and in particular the at least one further seal. Due to the sealing element according to the invention, the housing is arranged at a distance from the fuel cell stack and the further seal. In a vertical direction, the sealing element is preferably arranged between an inlet side and an outlet side of the fuel cell stack, but in each case to the side thereof.Since the fuel cells are sealed at both ends over the entire height of the fuel cell stack with the additional seal, at least one sealing element is also arranged on both sides of the fuel cell stack between the housing and the fuel cell stack.

[0009] Within the scope of the invention, the sealing device according to the invention is to be understood not only as the seal itself, but as described, as a sealing device comprising at least one fuel cell stack. The described seal can advantageously be used for any configuration and configuration, in particular SOFC fuel cell stacks, in order to create pressure equalization. Within the scope of the invention, it is particularly not necessary for the sealing element of the sealing device to be 100% leak-proof. For example, it can advantageously also be partially gas-permeable in order to create pressure equalization. Within the scope of the invention, the sealing element is, in particular, largely leak-proof.

[0010] Preferably, the at least one fuel cell stack is designed with an open cathode, whereby a single air flow is guided over the entire fuel cell stack(s). The housing limits the air flow to the outside. According to the invention, a portion of this air flow is also guided outside the fuel cell stack itself, at least to the sealing element. For example, the sealing element can advantageously be arranged approximately centrally of the additional seal in a plan view. This makes it possible for the air flow to flow outside the fuel cell stack on both the inlet and outlet sides. Consequently, the ambient pressure no longer acts on the additional sealing element, but rather the pressure of the air flow. A pressure difference is therefore reduced, and the additional sealing element(s) remain in place even at high temperatures.The distance between the housing and the fuel cell stack, which essentially corresponds to the thickness of the sealing element, should advantageously not exceed a defined width, so that a large portion of the air flow flows inside the fuel cell stack and not outside it. The fuel cell stack(s) are preferably flowed through by an air flow horizontally, with the anode path being substantially orthogonal to the air flow.

[0011] One or more fuel cell stacks are arranged within the housing, with a manifold for supplying anode feed gas or fuel being arranged, in particular, on their underside or at their vertically lowest point. Several, for example 50, individual fuel cells are located on this manifold, which are preferably flat and stacked one on top of the other to form a fuel cell stack. The fuel cell stacks are preferably designed with an open cathode, with the air flow being guided over all fuel cell stacks within the housing. This air flow is preferably directed laterally onto the fuel cell stacks in such a way that the air is guided between (and also to the side of) the ends of the fuel cells, which encompass the additional seal.Anode feed gas is supplied to the fuel cell stack at the bottom, flows through it essentially vertically upwards and is then led back down to the manifold, where the anode feed gas usually exits the manifold again.

[0012] It is advantageous if the sealing element is gas-tight or slightly porous. If the sealing element is slightly porous, a small portion of the air can flow through it, creating a pressure gradient between an inlet side and an outlet side of the fuel cell stack because the sealing element is slightly leaky. This pressure gradient outside the fuel cell stack (but inside the housing) essentially corresponds to the pressure gradient inside the fuel cell stack. If, in contrast, the sealing element is gas-tight, the pressure on the outlet side of the fuel cell stack prevails above the sealing element, and the pressure on the inlet side of the fuel cell stack prevails below it. The sealing element can preferably be made of an aluminum silicate, sealing mat, swell mat, or similar materials.

[0013] It is advantageous if the sealing element extends either over an entire side of the at least one fuel cell stack or only over a part thereof. In a first possible variant, the sealing element advantageously extends over the entire depth and / or height of a fuel cell stack, wherein this is then advantageously designed to be porous so that pressure equalization can take place between a fuel cell inlet side and a fuel cell outlet side. In another possible variant, the sealing element extends only over part of a height of the fuel cell stack, wherein this can advantageously be arranged approximately in the middle of a height and / or depth of the fuel cell stack. However, it can also be arranged, for example, at a lower or upper end of the fuel cell system. In this variant, the sealing element can advantageously be designed to be gas-tight or somewhat gas-permeable.In principle, it can also be advantageous if two or more sealing elements are arranged on each side of the fuel cell stack, with these elements being spaced apart by a predetermined distance.

[0014] It is expedient if a plurality of fuel cell stacks are arranged within the housing, wherein each fuel cell stack has at least one further seal and a sealing element is arranged between the further seal of each two fuel cell stacks. The individual fuel cell stacks are advantageously stacked both on top of one another and next to one another, so that a type of wall or array is formed. When arranged next to one another, each fuel cell stack comprises at least one separate further seal on each side of the same. Between two fuel cell stacks, a sealing element is advantageously provided for both fuel cell stacks, which sealing element always shares two fuel cell stacks. As described above, two or more sealing elements can also be arranged vertically one above the other between two fuel cell stacks.If two or more fuel cell stacks are arranged one above the other, each fuel cell stack includes its own manifold for supplying the anode feed gas. The sealing element can, for example, extend over the entire height of all fuel cell stacks. In such an arrangement of multiple fuel cell stacks, these are advantageously designed with an open cathode so that they can be jointly exposed to and through a single air flow. The fuel cell stacks are enclosed by a common housing.

[0015] It is advantageous if the sealing element has a capillary element or can be bypassed by a capillary element. If the sealing element is designed to be gas-tight, a capillary element for the defined passage of air can be advantageous, so that air can also flow outside the fuel cell stack from a fuel cell inlet to a fuel cell outlet. The capillary element is designed in particular as a pressure-communicating tube. The capillary element can either pass directly through the sealing element or be designed as a type of bypass that runs around the housing and bypasses the sealing element. The capillary element is made, for example, from steel or a corresponding alloy.

[0016] It is advantageous if one, two, three, or more sealing elements are arranged between the additional seal and the housing and / or between the additional seal of a first fuel cell stack and the additional seal of a further fuel cell stack. The sealing elements are arranged vertically one above the other on each side of a fuel cell stack and spaced apart from each other. By arranging two or more sealing elements, air flow outside the fuel cell stack can be even better controlled.

[0017] When manufacturing the sealing device, it can be advantageous if the sealing element is pressed onto the additional seal of the fuel cell stack. This is advantageous because it is not absolutely necessary for the sealing element to be gas-tight with the additional seal.

[0018] The object is alternatively achieved according to the invention in that, in a sealing device of the type mentioned at the outset, a predetermined air gap for pressure equalization is arranged between the housing and the further seal.

[0019] One advantage achieved in this way is that the housing no longer directly adjoins the additional seal, but rather the air gap is arranged between the housing and the additional seal. The air gap can therefore be viewed as a buffer device, with the housing no longer directly adjoining the fuel cell stack. This is an alternative to the sealing element, which essentially offers the same advantages as detailed above.

[0020] It is advantageous for both the sealing element and air gap designs if the housing is indirectly connected to the additional seal. At least one additional seal is provided on each side of the fuel cell stack, which does not directly connect to the housing. Either one sealing element or an air gap is provided on both sides of the fuel cell stack, allowing pressure equalization between an inlet and an outlet of the fuel cell stack.

[0021] The sealing device according to the invention with at least one fuel cell stack is advantageously used in an SOFC fuel cell system, which is preferably designed or used as a stationary system. A corresponding SOFC fuel cell system advantageously comprises further elements such as a reformer, an afterburner, several heat exchangers, optionally a recirculation section as well as several lines, valves and the like. If several fuel cell stacks are present, it is advantageous if these are arranged in a type of matrix, wherein those fuel cell stacks which are stacked one above the other in a row are electrically connected to one another. The fuel cell stacks arranged next to one another should be electrically insulated from one another. The sealing element or the air gap itself can advantageously be used for this purpose and, for example, ceramic insulation can be dispensed with.

[0022] Further advantages, features, and details of the invention will become apparent from the following description, which describes embodiments of the invention in detail with reference to the drawing. It shows schematically:

[0023] Fig. 1 is a schematic representation of a plan view of a sealing device according to the invention;

[0024] Fig. 2 is a schematic representation of a plan view of another sealing device according to the invention;

[0025] Fig. 3 is a schematic representation of a plan view of another sealing device according to the invention; Fig. 4 is a schematic representation of a plan view of another sealing device according to the invention;

[0026] Fig. 5 is a schematic representation of a section through another sealing device according to the invention;

[0027] Fig. 6 is a schematic representation of a plan view of another sealing device according to the invention.

[0028] Fig. 1 shows a plan view of a sealing device 1 according to the invention with a fuel cell stack 2. The fuel cell stack 2 comprises a plurality of fuel cells 4, which are not identified in Fig. 1. Since this figure represents a plan view, exactly one fuel cell 4 can be seen from above, since the others are stacked underneath. The fuel cell stack 2 is arranged within a housing 3. The individual fuel cells 4 are electrically sealed at their two lateral ends with a further seal 5 between the individual elements of the fuel cells 4. The further seal 5 is made of glass and extends over the entire height and preferably depth of the fuel cell stack 2. The fuel cell stack 2 is designed with an open cathode, such that an air flow L can be guided over the entire surface of the fuel cell stack 2. Between the housing 3 and the fuel cell stack 2 orThe additional seal 5 has a sealing element 6 arranged on both sides of the fuel cell stack 2. According to Fig. 1, this sealing element is located approximately halfway down the fuel cell stack 2 and is gas-tight or porous. The housing 3 is spaced from the fuel cell stack 2 by the sealing element 6, so that the air flow L does not pass entirely through the fuel cell stack 2, but rather a portion of it also passes to the right and left of it. This ensures that the pressure outside the fuel cell stack 2 essentially corresponds to that in the fuel cell stack 2. Since the air can flow at least as far as the sealing element 6 even when the fuel cell stack 2 exits, it is ensured that the additional seal 5 does not have to withstand the pressure outside the housing 3. If the sealing element 6 is porous, this means that a certain amount of air can also penetrate through the sealing element 6.

[0029] All figures, which show a top view of the sealing device 1 according to the invention, are traversed by the air flow L in the direction of a depth of the fuel cell stack 2, with the additional seals 5 being arranged laterally on the fuel cell stacks 2. An anode feed gas or fuel is guided essentially from bottom to top in the fuel cell stack, with a fuel outlet again being arranged on a lower side, and the individual fuel cells 4 naturally also being supplied with fuel horizontally.

[0030] For clarity, the distance between the housing 3 and the additional seal 5, or rather the sealing element 6, is shown quite large in all figures. It is understood that this distance should be small enough that the majority of the air flows through the fuel cell stack 2 itself, with only a predetermined portion flowing past it to the right and left.

[0031] Fig. 2 shows a plan view of a further sealing device 1 according to the invention. Elements which have the same function and in particular the same arrangement as those according to Fig. 1 also have the same reference numerals and will not be described further. In contrast to Fig. 1, in the sealing device 1 according to Fig. 2 the sealing elements 6 are the same height as the fuel cell stack 2 or extend over the entire height and depth of the fuel cell stack 2 and the further seals 5. In this case, the sealing elements 6 are porous so that a predetermined proportion of air can pass through them and a pressure gradient between the housing 3 and the further seal 5 essentially corresponds to that within the fuel cell stack 2.

[0032] Fig. 3 shows a plan view of a further sealing device 1 according to the invention. Elements which have the same function and in particular the same arrangement as those according to Fig. 1 and / or Fig. 2 also have the same reference numerals and will not be described further. This is a view in which three fuel cell stacks 2 are arranged next to one another. Several fuel cell stacks 2 can also be arranged one above the other. It can be seen that a sealing element 6 is provided not only between the fuel cell stack 2 with the further seal 5 and the housing 3, but also between each two fuel cell stacks 2. One sealing element 6 is sufficient for two fuel cell stacks 2. A further advantage of such an arrangement is that the sealing element 6 also makes separate electrical protection horizontally between the individual fuel cell stacks 2 possible.The sealing element 6 itself also forms an electrical seal. The individual fuel cell stacks 2 are to be electrically connected to one another vertically. The housing 3 contains all of the fuel cell stacks 2, and the air flow L hits and flows through all of the fuel cell stacks simultaneously. Fig. 3 shows two different possibilities for the arrangement and design of the sealing elements 6: Two sealing elements 6 are arranged one between two fuel cell stacks 2, and two between a fuel cell stack 2 and the housing 3, with these sealing elements being arranged at the two lateral ends of the fuel cell 2. The other two sealing elements 6 shown extend across the entire depth of the fuel cell stack 2. It is understood that the arrangements and designs of the sealing elements 6 are shown here only as examples. Any number can be provided and combined.These can be different as shown here, or all sealing elements 6 per sealing device 1 can be of the same design.

[0033] Fig. 4 shows a plan view of a further sealing device 1 according to the invention. Elements which have the same function and in particular the same arrangement as those according to Fig. 1 and / or Fig. 2 and / or Fig. 3 also have the same reference numerals and will not be described further. This sealing device 1 again comprises a plurality of fuel cell stacks 2, wherein the sealing elements 6 are arranged approximately in the center of the fuel cell stacks 2 and do not extend over their entire depth. In this sealing device 1, capillary elements 7 are provided, which are either passed through the gas-tight sealing element 6 (see sealing elements 6 between two fuel cell stacks 2) or form a pressure-communicating bypass around the sealing element 6 (see sealing elements 6 between fuel cell stack 2 and housing 3).The capillary elements 7 are essentially small tubes designed such that the pressure at an inlet side essentially corresponds to that at an outlet side of the fuel cell stack 2. It is understood that the arrangements of the capillary elements 7 are shown here only as examples. They can either all pass through the sealing elements 6, or all be designed as a bypass, or they can be combined in any desired way.

[0034] Fig. 5 shows a plan view of a sealing device 1 according to the invention with several fuel cell stacks 2. Elements which have the same function and in particular the same arrangement as those according to Fig. 1 and / or Fig. 2 and / or Fig. 3 and / or Fig. 4 also have the same reference numerals and will not be described further. In this view, the individual fuel cells 4 are shown schematically, although it is understood that these usually extend across the entire width of the fuel cell stack 2. For the sake of clarity, not all fuel cells 4 are shown. In this illustration, the air flow L would lead into the plane of the page. On the underside of the fuel cell stacks 2, a manifold 9 for supplying anode feed gas or fuel can be seen. The sealing device 1 according to the invention can advantageously also have one or more vertical rows of fuel cell stacks 2 with the elements as in Fig.5, wherein the individual rows are then stacked one above the other and all arranged within a common housing 3. Each fuel cell stack 2 comprises its own manifold 9, but the air flow L passes through all fuel cell stacks 2 together, since they are designed with an open cathode.

[0035] Fig. 6 shows a second variant of the sealing device 1 according to the invention. This does not comprise a sealing element 6, but rather an air gap 8 is provided in order to create pressure equalization between a fuel cell inlet and a fuel cell outlet. Here, too, the air flow L not only passes through the respective fuel cell stacks 2, but air also gets between the fuel cell stacks 2 and between the fuel cell stack 2 and the housing 3. In Fig. 6, too, the respective air gap 8 is always shown as oversized. Elements which have the same function and in particular the same arrangement as those according to Fig. 1 and / or Fig. 2 and / or Fig. 3 and / or Fig. 4 and / or Fig. 5 also have the same reference numerals and will not be described further.

Claims

Claims: Sealing device (1) for at least one fuel cell stack (2), in particular a SOFC fuel cell stack, comprising a housing (3) and at least one fuel cell stack (2) arranged or arrangable within the housing (3), wherein the at least one fuel cell stack (2) comprises several fuel cells (4), the fuel cells (4) having at least one further seal (5) at their lateral ends, the housing (3) surrounding the at least one fuel cell stack (3) with the further seal (5), characterized in that at least one sealing element (6) for pressure equalization is arranged between the housing (3) and the further seal (5). Sealing device (1) according to claim 1, characterized in that the sealing element (6) is gas-tight or slightly porous.A sealing device (1) according to claim 1 or 2, characterized in that the sealing element (6) extends either over an entire side of the at least one fuel cell stack (2) or only over a part thereof. A sealing device (1) according to any one of claims 1 to 3, characterized in that several fuel cell stacks (2) are arranged within the housing (3), each fuel cell stack (2) having at least one further seal (5) and a sealing element (6) being arranged between the further seal (5) of each of two fuel cell stacks (2). A sealing device (1) according to any one of claims 1 to 4, characterized in that the sealing element (6) has a capillary element (7) or can be bypassed by a capillary element (7).Sealing device (1) according to one of claims 1 to 5, characterized in that one, two, three or more sealing elements (6) are arranged between the further seal (5) and the housing (3) and / or between the further seal (5) of a first fuel cell stack (2) and the further seal (5) of a further fuel cell stack (2). A sealing device (1) for at least one fuel cell stack (2), in particular a SOFC fuel cell stack, comprising a housing (3) and at least one fuel cell stack (2) arranged or arrangable within the housing (3), wherein the at least one fuel cell stack (2) comprises several fuel cells (4), the fuel cells (4) having at least one further seal (5) at their lateral ends, the housing (3) surrounding the at least one fuel cell stack (3) with the further seal (5), characterized in that a predetermined air gap (8) for pressure equalization is arranged between the housing (3) and the further seal (5). A sealing device (1) according to any one of claims 1 to 7, characterized in that the housing (3) connects indirectly to the further seal (5).Fuel cell system, in particular SOFC fuel cell system, comprising a sealing device according to one of claims 1 to 8 with multiple fuel cell stacks (2).

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