Filter medium for the cathode feed air of a fuel cell unit

Abstract

The present invention relates to a filter medium (1) for purifying a cathode gas of a fuel cell unit (102). Improved efficiency and cost-effective implementation are achieved by virtue of the filter medium (1) having a particle filter layer (2) for filtering particles from the cathode feed air, a gas filter layer (3) for removing harmful gases from the cathode feed air and a carrier layer (4) for carrying the filter medium (1), the layers being connected to each other and following one another, wherein the gas filter layer (3) contains activated carbon (5) and ion exchangers (6). The invention also relates to a fuel cell system (100) comprising a fuel cell unit (102), which has at least one fuel cell (101), and such a filter medium (1).

Description

[0001] Filter medium for the cathode supply air of a fuel cell unit

[0002] The present invention relates to a filter medium for the cathode supply air of a fuel cell unit. The invention also relates to a fuel cell system with such a filter medium.

[0003] A fuel cell requires an oxygen-containing cathode supply air and a hydrogen-containing reducing agent. Within the fuel cell, a controlled reaction of the cathode supply air with the reducing agent takes place, with the fuel cell providing electrical energy for extraction.

[0004] For the quality and efficiency of the fuel cell, it is advantageous to supply the reactants and especially the cathode supply air to the fuel cell as pure as possible.

[0005] US 10,046,271 B2 describes an air purifier for the cathode supply air of a fuel cell. The air purifier has a first filter for removing dust from the cathode air and a second filter for removing gases from the cathode air. The second filter follows the first filter along the flow of the cathode gas and can be arranged adjacent to the first filter.

[0006] The present invention addresses the problem of providing improved or at least alternative embodiments of a filter medium for the cathode air supply of a fuel cell, as well as for a fuel cell system with such a filter medium. In particular, the present invention addresses the problem of providing embodiments of the filter medium and the fuel cell system that are characterized by an increased service life and / or improved efficiency. This problem is solved according to the invention by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

[0007] The invention is therefore based on the fundamental idea of ​​constructing a multi-layered filter medium for the cathode supply air of a fuel cell. In addition to a supporting layer, one of these layers serves to filter particles from the cathode supply air, and another of these layers serves to filter harmful gases from the cathode supply air, and for this purpose comprises activated carbon and ion exchangers. Thus, both the filtration of particles from the cathode supply air and the reduction of harmful gases in the cathode supply air are implemented within one filter medium and thus a coherent unit. The standardization of the filtration of particles and the removal of harmful gases from the cathode supply air in one filter medium leads to a reduction in the total number of supporting layers required. As a result, the pressure drop resulting from filtration is reduced.Thus, the cathode supply air can reach the fuel cell at increased pressure and / or with reduced effort while maintaining the same filter performance, allowing the fuel cell to operate with increased overall efficiency. The basic concept of the invention also leads to a cost-effective implementation and simplified use of the filter medium in an associated fuel cell system.

[0008] According to the inventive concept, the filter medium has a permeable and supporting layer for supporting the filter medium, which is also referred to below as the carrier layer. The filter medium also has a layer for filtering particles from the cathode supply air, which is also referred to below as the particle filter layer. The filter medium also has a layer for removing harmful gases from the cathode supply air, which comprises activated carbon and ion exchangers and is also referred to below as the gas filter layer. The layers of the filter medium are interconnected and follow one another. The filter medium serves to filter the cathode supply air, which then flows to a fuel cell.

[0009] The fuel cell is advantageously part of a fuel cell unit. The fuel cell unit advantageously comprises two or more consecutive or stacked fuel cells. Thus, the filter medium serves to filter the cathode supply air for the fuel cell unit.

[0010] The fuel cell unit is usually part of a fuel cell system, which also has a system for supplying the cathode supply air to the at least one fuel cell. This system is also referred to below as the cathode gas supply system. A flow path for the cathode supply air for the fuel cell unit runs through the cathode gas supply system. During operation, the cathode supply air flows via the cathode gas supply system to the at least one fuel cell. The fuel cell system also has the filter medium, which is arranged in the cathode gas supply system, so that the cathode supply air flows through the filter medium upstream of the fuel cell unit, and the filter medium filters and thus cleans the cathode supply air. The flow path runs through the layers of the filter medium.

[0011] The filter medium can be part of a filter device arranged upstream of the fuel cell unit in the cathode gas supply system. The filter device can, for example, comprise a housing accommodating the filter medium and / or at least one seal.

[0012] During fuel cell operation, the oxygen contained in the cathode supply air is reacted with a reducing agent. The oxygen-containing cathode supply air is, for example, fresh air supplied from outside. The reducing agent contains hydrogen, for example, hydrogen. The cathode supply air is fed to a cathode compartment or cathode of the fuel cell, and the reducing agent is fed to an anode compartment or anode of the fuel cell. To enable a controlled reaction, which can be used to generate electrical energy, the cathode compartment is separated from the anode compartment. The separation can be achieved using a membrane, such as a Nafion® membrane.

[0013] The separation between the cathode compartment and the anode compartment, in particular the membrane, is advantageously coated on both sides with a catalytically active electrode. Such a catalytically active electrode can contain, for example, carbon and platinum or a mixture of platinum and at least one other metal. Both the membrane and the catalytically active electrodes are sensitive to harmful gases and particles in the cathode supply air and can be damaged both reversibly and irreversibly by them. Such damage can lead to a decrease in performance and even failure of the fuel cell. The filter medium prevents or at least reduces such damage and simultaneously increases the efficiency of the fuel cell system.

[0014] The cathode supply air advantageously flows downstream of the filter medium, in particular the filter device, to a humidifier to humidify the filtered cathode supply air before it flows into the fuel cell unit. Humidification can be achieved, for example, using a humid medium via membranes that are permeable to gaseous water and / or partially condensed water. Examples of such membranes are perfluorinated sulfonic acid-based (PFSA) polymer membranes, such as Nafion® membranes, or other hydrophilic polymer membranes, for example, those based on polyacrylonitriles or so-called polymer composite membranes. These membranes are also sensitive to particles and harmful gases entrained in the cathode supply air. In particular, coating / wetting of the membrane with particles and harmful gases can lead to a reduction in performance or even failure of the humidifier.Particles can also clog the spaces between the membranes through which the cathode supply air flows, leading to reduced efficiency and even failure of the humidifier. Such failures and damage are also prevented or at least reduced by the filter medium, while simultaneously increasing the efficiency of the fuel cell system.

[0015] In this context, "harmful gases" are defined as gaseous compounds entrained in the cathode supply air that can, in particular, lead to damage to the membranes and / or the catalytically active electrodes. These harmful gases include, for example, nitrogen oxides, ammonia, sulfur oxides, dihydrogen sulfide, ozone, and volatile organic carbon compounds.

[0016] “Volatile organic carbon compounds” are gaseous compounds of organic origin, such as hydrocarbons, aldehydes and organic acids. These are often divided into very volatile organic carbon compounds, volatile organic carbon compounds and semi-volatile organic carbon compounds based on their boiling range. Very volatile organic carbon compounds, or “WOG” for short, include formaldehyde. Benzene is a volatile organic compound, or “VOC” for short. Some plasticizers are semi-volatile organic compounds, or “SVOC” for short, for example.

[0017] Accordingly, the filter medium, in particular the gas filter layer, is designed to remove, in particular to adsorb and / or absorb, these gases.

[0018] The pollutants filtered by the filter medium include NOx, SO2, H2S and NH3, as well as toluene, ozone, n-butane, benzene, and volatile hydrocarbons.

[0019] The layers of the filter medium are bonded together. The layers are preferably bonded together by a material bond, for example, by adhesive bonding. For example, the layers are stacked on top of each other, pressed, and laminated. Alternatively or additionally, the layers can be bonded together, for example, at the cut edges, linearly and at specific points across the surface, using ultrasonic welding and / or thermal calendering.

[0020] The layers of filter medium can be arranged in any order. "Consecutive" preferably refers to the sequence along a designated flow direction of the cathode supply air. This means that the layers are arranged in such a way that the cathode supply air flows through them one after the other during operation. In other words, the flow path of the cathode supply air leads through the layers one after the other. The order of the layers determines / defines which type of filtration takes place successively.

[0021] In principle, the layers of the filter medium can each have any shape. It is generally possible for the respective layer, especially the filter medium, to be flat and even.

[0022] The gas filter layer of the filter medium is advantageously folded. The folding direction expediently and preferably runs transversely to the sequential arrangement of the layers. This means, in particular, that the gas filter layer is folded transversely to the flow direction. In particular, at least the gas filter layer forms a bellows. The folding of the gas filter layer results in the filter medium having more activated carbon and ion exchanger for the same available volume and thus installation space. This means that the filter medium has a higher volume density of activated carbon and ion exchanger. This results in an improved filtering effect, in particular in reduced perforation. Variants in which the layers, i.e. all layers, of the filter medium are folded are preferred. The layers of the filter medium thus form a bellows. The layers are preferably folded together.The folding direction is expediently and preferably perpendicular to the sequential arrangement of the layers. This means, in particular, that the layers are folded perpendicular to the flow direction. This results in an optimized pressure drop across the filter medium. This means that the flow resistance across the filter medium is reduced or at least optimized.

[0023] In advantageous embodiments, the entire filter medium is pleated. The filter medium is thus designed as a bellows.

[0024] In advantageous variants, the gas filter layer is arranged between the particle filter layer and the carrier layer.

[0025] In preferred variants, the particle filter layer is arranged after the gas filter layer along the intended flow path. This means that the particle filter layer is preferably arranged downstream of the gas filter layer. Thus, pollutants and ions are filtered out of the cathode supply air first, followed by particles from the cathode supply air.

[0026] It is conceivable that a further layer / component of the filter medium is arranged between at least two of the successive layers.

[0027] In preferred embodiments, the layers of the filter medium, i.e. the carrier layer, the gas filter layer, and the particle filter layer, adjoin one another directly. This leads in particular to a further reduced pressure drop when flowing through the filter medium and consequently to a further increase in the efficiency of the fuel cell system with the same or at least comparable filter performance. A "layer" is understood here to mean a coherent unit with a thickness running along the flow direction. The respective layer can consist of a single layer. The respective layer can also have at least two consecutive layers, wherein the layers differ from one another, for example in their composition.

[0028] As described above, the particle filter layer serves to filter particles from the cathode supply air. In this case, this means in particular that the primary purpose of the particle filter layer is to filter particles from the cathode supply air. For example, the particle filter layer filters dust from the cathode supply air.

[0029] As described above, the gas filter layer serves to remove, i.e., filter, harmful gases from the cathode supply air. In this case, this means, in particular, that the main purpose of the gas filter layer is to remove harmful gases from the cathode supply air.

[0030] As described above, the carrier layer serves to support the filter medium. In this case, this means, in particular, that the primary purpose of the permeable carrier layer is to support the filter medium and, preferably, to maintain the mechanical stability of the entire filter medium.

[0031] The removal of harmful gases from the cathode supply air is advantageously carried out by means of the activated carbon and / or ion exchanger contained in the gas filter layer. The activated carbon is advantageously designed to remove said harmful gases from the cathode supply air by adsorption. The ion exchanger is preferably designed to remove said harmful gases from the cathode supply air by absorption. The gas filter layer can comprise impregnated activated carbon and / or unimpregnated activated carbon. In particular, the impregnated activated carbon can comprise potassium carbonate, i.e., K2CO3.

[0032] The activated carbon advantageously comprises activated carbon particles, in particular, it consists of such particles. These particles are also referred to simply as activated carbon granules. The activated carbon can therefore consist of activated carbon granules.

[0033] The ion exchanger is advantageously designed in such a way that the ion exchanger binds anions and / or cations and thus removes them from the cathode supply air.

[0034] The ion exchanger is advantageously designed in such a way that it removes cations from the cathode gas, particularly by binding them to itself. The ion exchanger is therefore preferably a cation exchanger. The resulting reduction in the number of cations in the cathode chamber or at the cathode of the respective fuel cell results in improved operation, increased efficiency, and reduced degradation of the fuel cell components. Furthermore, the avoidance or at least reduction of cations in the cathode supply air leads to improved filtration of the cathode supply air by means of the activated carbon.

[0035] The ion exchanger advantageously contains sulfonic acid groups. This creates a toxic environment for organisms locally in the area of ​​the ion exchanger.

[0036] The ion exchanger, for example, comprises macroporous polystyrene cross-linked with divinylbenzene.

[0037] The ion exchanger can be at least partially fibrous and incorporated into a nonwoven layer with filter material fibers. The filter material fibers advantageously comprise, and in particular consist of, plastic fibers and / or cellulose fibers or a mixture thereof.

[0038] The ion exchanger advantageously comprises particles made of ion exchangers, in particular, it consists of such particles. These particles are also referred to simply as ion exchanger granules. The ion exchanger can therefore consist of ion exchanger granules.

[0039] The ion exchange granules can be incorporated into a nonwoven layer with filter material fibers, whereby plastic fibers and / or cellulose fibers or a mixture are preferably used for the nonwoven layer.

[0040] The activated carbon and ion exchangers can be arranged and / or distributed as desired in the gas filter layer.

[0041] The gas filter layer advantageously comprises at least one activated carbon layer with activated carbon and at least one ion exchange layer with ion exchangers, which are arranged in succession. The proportion of activated carbon in each activated carbon layer is greater, in particular considerably greater, than the proportion of ion exchangers. In particular, each activated carbon layer can be substantially free of ion exchangers. Conversely, the proportion of ion exchangers in each ion exchange layer is greater, in particular considerably greater, than the proportion of activated carbon. In particular, each ion exchange layer can be substantially free of activated carbon. During operation, the cathode supply air thus comes into contact with activated carbon and ion exchangers one after the other. This results in improved filtration of the cathode supply air.

[0042] Embodiments in which at least one of the at least one ion exchange layers directly adjoins at least one of the at least one activated carbon layers are considered advantageous. Preferably, the at least one ion exchange layer and the at least one activated carbon layer directly adjoin one another.

[0043] The gas filter layer can advantageously consist of at least one activated carbon layer and at least one ion exchange layer.

[0044] In principle, the respective activated carbon layer can contain both impregnated and unimpregnated activated carbon.

[0045] At least one of the at least one activated carbon layers may comprise predominantly impregnated activated carbon. These activated carbon layers are also referred to below as impregnated activated carbon layers.

[0046] It is preferred if the respective impregnated activated carbon layer comprises impregnated activated carbon as its main component. The weight fraction of impregnated activated carbon in the respective impregnated activated carbon layer is preferably at least 70%, preferably at least 90%, for example 95%. The weight fraction of non-activated carbon particles in the respective impregnated activated carbon layer can be up to 10%.

[0047] At least one of the at least one activated carbon layers may comprise predominantly unimpregnated activated carbon. These activated carbon layers are also referred to below as unimpregnated activated carbon layers.

[0048] The respective unimpregnated activated carbon layer expediently comprises unimpregnated activated carbon as its main component. The weight fraction of unimpregnated activated carbon in the respective unimpregnated activated carbon layer is preferably at least 70%, preferably at least 90%, for example 95%. For example, the gas filter layer can comprise two consecutive unimpregnated activated carbon layers and a subsequent ion exchange layer, in particular consisting of these layers.

[0049] Advantageously, the ion exchange layer follows the activated carbon layers. The gas filter layer thus has at least two, in particular exactly two, activated carbon layers and one ion exchange layer, with the ion exchange layer following the activated carbon layers.

[0050] Likewise, at least one ion exchange layer can be arranged between two activated carbon layers. This means that activated carbon layers and ion exchange layers can alternate.

[0051] It is conceivable to also design the gas filter layer to store particles, especially dust. For this purpose, the gas filter layer advantageously has a corresponding layer, which is also referred to below as a dust storage layer.

[0052] Preferably, the dust storage layer is arranged between at least one of the at least one activated carbon layers and at least one of the at least one ion exchange layers. The gas filter layer can therefore advantageously comprise a dust storage layer for storing particles, which is arranged between at least one of the at least one activated carbon layers and at least one of the at least one ion exchange layers.

[0053] The dust storage layer can be similar in design to the particle filter layer. Preferably, the dust storage layer has a higher storage capacity for particles, particularly dust, than the particle filter layer.

[0054] The gas filter layer can also have a layer containing activated carbon and ion exchangers, particularly activated carbon granules and ion exchange granules. This layer is also referred to below as the mixed layer. Activated carbon and ion exchangers, particularly activated carbon granules and ion exchange granules, are advantageously distributed evenly / homogeneously in the mixed layer.

[0055] The activated carbon granules and the ion exchange granules in the mixed layer and / or in the respective activated carbon layer or ion exchange layer are expediently fixed / held in the gas filter layer. This can be achieved, for example, using an adhesive. The adhesive can be, for example, a polypropylene hotmelt. Alternatively or additionally, the gas filter layer, in particular the respective associated layer, can contain polymer fibers that are melted to fix the granules.

[0056] At least one of the at least one activated carbon layer, preferably the respective activated carbon layer, advantageously has a grammage of between 150 g / m 2 and 300 g / m 2 For example, the grammage is 160 g / m 2 .

[0057] Likewise, at least one of the at least one activated carbon layer can have a grammage between 240 g / m 2 and 260 g / m 2In particular, the grammage can be 250 g / m 2 be.

[0058] The aforementioned grammage of the activated carbon layer results in high adsorption performance, while simultaneously optimizing and, in particular, reducing the flow resistance of the activated carbon layer and thus of the filter medium. This results in a combination of high adsorption performance and reduced pressure loss in the cathode supply air. The latter leads to a further increase in the efficiency of the associated fuel cell system.

[0059] Embodiments are considered advantageous in which the respective impregnated activated carbon layer has a grammage between 140 g / m 2 and 180 g / m 2 For example, the grammage can be 160 g / m 2This combines high filtration performance with low pressure drop in the respective impregnated activated carbon layer and thus in the filter medium. This results in improved adsorption and simultaneously increased efficiency of the associated fuel cell system.

[0060] The activated carbon granules preferably have a grain size of 20x40 or 20x50 or 30x60 or 35x60.

[0061] At least one of the at least one ion exchange layer, preferably the respective ion exchange layer, advantageously has a grammage between 200 g / m 2 and 270 g / m 2 For example, the grammage is 220 g / m 2 or 250 g / m 2This leads to an effective exchange of ions from the cathode supply air while simultaneously reducing pressure drop in the filter medium. This results in a combination of improved ion absorption and increased efficiency in the associated fuel cell system.

[0062] As explained above, the main purpose of the particle filter layer is to filter particles from the cathode supply air.

[0063] In preferred embodiments, the particle filter layer is also designed to support the filter medium. This means that, in addition to filtering particles, the particle filter layer also serves to maintain the mechanical stability of the filter medium.

[0064] In advantageous embodiments, the carrier layer is designed to filter particles from the cathode supply air. This means that, in addition to supporting the filter medium, the carrier layer also serves to filter particles from the cathode supply air. Preferred variants are those in which the layer through which the air flows first in the flow direction filters larger / coarser particles from the cathode supply air than the layer through which the air flows next. Thus, if the carrier layer is arranged upstream of the particle filter layer, the carrier layer is preferably designed to filter larger particles from the cathode supply air, and the particle filter layer is preferably designed to filter smaller particles from the cathode supply air, for example, fine dust, or vice versa.

[0065] The particle filter layer can comprise any nonwovens, wovens, knitted fabrics or foams that enable mechanical separation of particles.

[0066] The particle filter layer preferably comprises nanofibers or fine meltblown fibers. This results in improved filtration of particles from the cathode supply air. The diameter of the nanofibers is advantageously between 10 nm and 800 nm. The diameter of the nanofibers is preferably between 100 nm and 500 nm. The diameter of the nanofibers is preferably between 100 nm and 120 nm.

[0067] The particle filter layer advantageously comprises a nonwoven fabric, which is also referred to below as a cover nonwoven. The cover nonwoven is advantageously made of fibers made of polyamide and / or polyester, such as fibers made of polyethylene terephthalate, and / or polyvinyl alcohol, and / or polypropylene. Isotactic, atactic, and / or syndiotactic polypropylene can be used. The polypropylene can be formed, for example, as a meltblown nonwoven.

[0068] The particle filter layer advantageously has a grammage between 30 g / m 2 and 70 g / m 2 For example, the grammage of the particle filter layer can be 40 g / m 2 , 45 g / m 2 or 60 g / m 2 be.

[0069] Preferred variants are those in which the cover fleece is light and open. The cover fleece preferably has a maximum grammage of 50 g / m 2 . The covering fleece preferably has a grammage between 10 g / m 2 and 20 g / m 2 , for example of approx. 16 g / m 2 In particular, the particle filter layer can comprise two polypropylene layers, for example a layer of meltblown nonwoven and a layer of spunbonded nonwoven.

[0070] Preferably, the grammage of the spunbonded fabric is between 5 g / m 2 and 25 g / m 2 In particular, the spunbonded fabric has a grammage of 15 g / m 2. This results in not only increased efficiency in particle filtration but also reduced pressure loss in the particle layer and thus increased efficiency of the associated fuel cell system.

[0071] Preferably, the meltblow fleece has a grammage of between 15 g / m 2 and 35 g / m 2 For example, the meltblow fleece has a grammage of 25 g / m 2 This results in high filtration efficiency and reduced pressure loss, thus simultaneously increasing the efficiency of the associated fuel cell system.

[0072] The carrier layer preferably has a layer of nonwoven fabric, which is also referred to below as nonwoven layer.

[0073] Preferred variants are those in which the fleece layer has a grammage of at least 40 g / m 2 Advantageously, the nonwoven layer has a grammage between 40 g / m 2 and 100 g / m2 , preferably between 45 g / m 2 and 75 g / m 2 , on.

[0074] The carrier layer may contain auxiliary materials. These include binders, crosslinkers, and additives. Examples of binders are acrylates and melamine formaldehyde. An example of an additive is polyurethane. The auxiliary materials are preferably present in the carrier layer in low weight concentrations. The proportion of the respective auxiliary material in the carrier layer is advantageously less than 2% by weight.

[0075] The filter medium can advantageously comprise, particularly in the direction of flow, a carrier layer, a first unimpregnated activated carbon layer, a second unimpregnated activated carbon layer, an ion exchange layer, and a particle filter layer in direct succession. The grammage of the carrier layer is preferably between 60 g / m 2 and 70 g / m 2 , especially 65 g / m 2, the grammage of the respective unimpregnated activated carbon layer between 240 g / m 2 and 260 g / m 2 , especially 250 g / m 2 , the grammage of the ion exchange layer between 210 g / m 2 and 230 g / m 2 , especially 220 g / m 2 and the grammage of the particle filter layer between 35 g / m 2 and 70 g / m 2 , especially 45 g / m 2 or 60 g / m 2 .

[0076] The filter medium can advantageously comprise, particularly in the direction of flow, a carrier layer, an impregnated activated carbon layer, an unimpregnated activated carbon layer, an ion exchange layer, and a particle filter layer in direct succession. The grammage of the carrier layer is preferably between 55 g / m 2 and 75 g / m 2 , especially 65 g / m 2 , the grammage of the impregnated activated carbon layer between 150 g / m 2 and 170 g / m 2 , especially 160 g / m 2, the grammage of the unimpregnated activated carbon layer between 150 g / m 2 and 170 g / m 2 , especially 160 g / m 2 , the grammage of the ion exchange layer between 240 g / m 2 and 260 g / m 2 , especially 250 g / m 2 and the grammage of the particle filter layer between 30 g / m 2 and 50 g / m 2 , especially 40 g / m 2 .

[0077] It is understood that in addition to the filter medium, the fuel cell system with the filter medium also belongs to the scope of this invention.

[0078] Preferably, the filter medium in the fuel cell system, in particular in the cathode gas supply system, is arranged such that the carrier layer is arranged upstream, i.e., the gas filter layer and the particle filter layer are flowed through.

[0079] Preferably, the particle filter layer is arranged downstream of the gas filter layer in the flow path and the gas filter layer is arranged downstream of the carrier layer.

[0080] The fuel cell system advantageously comprises a compressor integrated into the cathode gas supply system for compressing the cathode supply air. The compressor is advantageously integrated downstream of the filter medium, in particular the filter device, in the cathode gas supply system.

[0081] Advantageously, the fuel cell system has a cooler downstream of the compressor for cooling the cathode supply air. The cooler is preferably arranged between the compressor and the humidifier in the cathode gas supply system.

[0082] The compressor can be driven by a turbine which is integrated into a system for removing the exhaust gas generated in the at least one fuel cell during operation, i.e. can be a component of an exhaust gas turbocharger.

[0083] The fuel cell system can be used in stationary applications, such as a combined heat and power plant, a power generator, and the like. Applications in private households or businesses for power generation are also conceivable.

[0084] The fuel cell system can also be used in a mobile application, for example in a motor vehicle, in particular in a bus, a car, a truck, an agricultural machine and the like.

[0085] The fuel cell system can also be used in a construction machine, a ship, a train, an aircraft and the like.

[0086] Further important features and advantages of the invention emerge from the subclaims, from the drawings and from the associated description of the figures based on the drawings.

[0087] It is understood that the features mentioned above and those to be explained below can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the present invention. Preferred embodiments of the invention are illustrated in the drawings and explained in more detail in the following description, wherein like reference numerals refer to the same or similar or functionally identical components.

[0088] They show, schematically

[0089] Fig. 1 is a highly simplified, circuit diagram-like representation of a fuel cell system with a filter medium,

[0090] Fig. 2 to 9 each show a simplified sectional view of the filter medium in a different embodiment,

[0091] Fig. 10 a simplified side view of the filter medium,

[0092] Fig. 11 is a simplified representation of the element designated XI in Figure 10.

[0093] area.

[0094] A filter medium 1, as shown by way of example in the figures, is used in a fuel cell system 100, which is shown by way of example and in a highly simplified manner in Figure 1. As indicated in Figure 1, the fuel cell system 100 can be used in a motor vehicle 200 not otherwise shown, for example in a bus, a truck, an agricultural machine, and the like.

[0095] The fuel cell system 100 has a fuel cell unit 102 comprising at least one fuel cell 101. In the exemplary embodiment shown, as indicated in Figure 1, the fuel cell unit 102 has at least two stacked fuel cells 101. Five fuel cells 101 can be seen in Figure 1 purely as an example. During operation, the at least one fuel cell 101 is supplied with oxygen-containing cathode supply air via a system 103, which is also referred to below as cathode gas supply system 103. The cathode gas supply system 103 thus serves to supply the cathode supply air to the at least one fuel cell 101. A flow path 104 of the cathode supply air leads through the cathode gas supply system 103. The cathode supply air can, for example, be ambient air.The at least one fuel cell 101 is also supplied with a hydrogen-containing reducing agent via a system 105 of the fuel cell system 100, which is also referred to below as the reducing agent supply system 105. The reducing agent thus flows, as indicated by an arrow in Figure 1, through the reducing agent supply system 105 to the at least one fuel cell 101. The exhaust gas from the at least one fuel cell 101, i.e., in particular, water vapor, is removed by means of a system 106, which is also referred to below as the exhaust gas removal system 106. The exhaust gas thus flows, as indicated by an arrow in Figure 1, out of the at least one fuel cell 101 via the exhaust gas removal system 106.

[0096] The filter medium 1 serves to clean the cathode supply air to be supplied to the at least one fuel cell 101. For this purpose, the flow path 104 of the cathode supply air passes through the filter medium 1. The filter medium 1 is arranged in the cathode gas supply system 103 and, with respect to the flow of the cathode gas, i.e., along the flow path 104, upstream of the at least one fuel cell 101 and thus upstream of the fuel cell unit 102. As indicated in Figure 1, the filter medium 1 is a component of a filter device 107 in the illustrated embodiment.

[0097] In the illustrated embodiment, the fuel cell system 100 also includes a compressor 108, which compresses the cathode supply air after it flows through the filter medium 1. In the illustrated embodiment, the compressor 108 is part of an exhaust gas turbocharger 109, which also includes a turbine 110 integrated into the exhaust gas removal system 106. In the illustrated embodiment, the fuel cell system 100 also includes a cooler 111 for cooling the cathode supply air, through which the cathode supply air flows after compression by the compressor 108. The compressor 108 is thus integrated downstream of the filter medium 1, and the cooler 111 is integrated downstream of the compressor 108 in the cathode gas supply system 103. In the embodiment shown, the fuel cell system 100 also has a humidifier 112 for humidifying the cathode supply air upstream of the at least one fuel cell 101.The humidifier 112 is arranged downstream of the filter medium 1, in the illustrated embodiment downstream of the cooler 111. Thus, after cooling by the cooler 111, the cathode supply air is humidified in the humidifier 112. In the illustrated embodiment, the moisture required for this was generated from the exhaust gas of the at least one fuel cell 101. Accordingly, the humidifier 112 is also integrated into the exhaust gas removal system 106.

[0098] The structure of the filter medium 1 is explained in more detail below using Figures 2 to 11.

[0099] The filter medium 1 is therefore constructed in at least three layers, i.e., it has at least three layers 2, 3, 4. The layers 2, 3, 4 follow one another with respect to the flow direction 104 of the cathode gas through the filter medium 1 and are connected to one another, for example, by a material bond. In the illustrated embodiments, the filter medium 1 has a three-layer construction, i.e., it has only these three layers 2, 3, 4.

[0100] One of these layers 2 serves to filter particles from the cathode supply air and is hereinafter also referred to as particle filter layer 2. The main purpose of particle filter layer 2 is therefore to filter particles from the cathode supply air. Another of these layers 3 serves to absorb harmful gases from the cathode supply air and is hereinafter also referred to as gas filter layer 3. The main purpose of gas filter layer 3 is therefore to absorb harmful gases from the cathode supply air. For this purpose, gas filter layer 3 has activated carbon 5 and ion exchangers 6, which are greatly simplified and only indicated in Figure 2. The other layer 4 serves to support the filter medium 1 and is hereinafter also referred to as carrier layer 4. The carrier layer 4 is permeable, i.e., is flowed through by the cathode supply air during operation. In the embodiments shown, the layers 2, 3, 4 are directly adjacent to one another, as can be seen from Figures 2 to 9.

[0101] In the illustrated embodiments, the particle filter layer 2 comprises a nonwoven fabric made of fibers, preferably nanofibers or fine meltblown, which is also referred to below as a covering nonwoven and is not shown further. The grammage of the particle filter layer 2 is, for example, between 30 g / m 2 and 70 g / m 2 In the illustrated embodiments, the particle filter layer 2 comprises two polypropylene layers, for example, a layer of meltblown nonwoven and a layer of spunbonded nonwoven. The grammage of the spunbonded nonwoven is advantageously between 5 g / m 2 and 25 g / m 2 , especially 15 g / m 2 . The grammage of the meltblown nonwoven is advantageously between 15 g / m 2 and 35 g / m 2 , especially 25 g / m 2 .

[0102] In the illustrated embodiments, the carrier layer 4 comprises a nonwoven fabric (not shown), which is also referred to below as the nonwoven layer. In the illustrated embodiments, the nonwoven layer has a grammage of at least 40 g / m 2 , preferably between 45 g / m 2 and 75 g / m 2 ,. In addition, the carrier layer 4 can contain excipients, wherein the proportion of the respective excipient in the carrier layer is less than 2 wt.%.

[0103] As can be seen from the figures, in the exemplary embodiments shown, the gas filter layer 3 is arranged between the particle filter layer 2 and the carrier layer 4. Advantageously, the carrier layer 4 is arranged upstream of the gas filter layer 3 and the particle filter layer 2, as can be seen from Figures 2 and 4 to 9. The particle filter layer 2 is therefore arranged in the flow path 104 downstream of the gas filter layer 3 and the gas filter layer 3 downstream of the carrier layer 4. In these exemplary embodiments, the filter medium 1 is flowed through in such a way that the cathode supply air first flows through the carrier layer 4, then through the gas filter layer 3 and then through the particle filter layer 2. However, it is also possible for the particle filter layer 2 to be arranged upstream of the gas filter layer 3 and the carrier layer 4, as shown in Figure 3.In this embodiment, the filter medium 1 is thus flowed through in such a way that the cathode supply air first flows through the particle filter layer 2, then through the gas filter layer 3 and then through the carrier layer 4.

[0104] In the illustrated embodiments, the respective particle filter layer 2 is also designed to support the filter medium 1. In the illustrated embodiments, the respective carrier layer 4 is also designed to filter particles from the cathode supply air. Advantageously, the upstream layer 2, 4 is designed to filter coarser particles, and the downstream layer 2, 4 is designed to filter finer particles, for example, fine dust. For example, the particle filter layer 2 can comprise a nonwoven cover (not shown) with a maximum grammage of 50 g / m 2 In particular, the carrier layer 4 may comprise a nonwoven layer (not shown) with a grammage of at least 40 g / m 2, especially between 40 g / m 2 and 100 g / m 2 , for example between 45 g / m 2 and 75 g / m 2 , have.

[0105] The gas filter layer 3 can, as can be seen in the exemplary embodiments of Figures 2 to 8, have two or more individual layers 7, 8, which follow one another along the flow path 104. The gas filter layer 3 can, as shown in the exemplary embodiments of Figures 2 to 8, have at least one layer 7 with activated carbon 5, which is also referred to below as the activated carbon layer 7. In the activated carbon layer 7, no ion exchangers 6 are present, or their proportion is very small compared to the activated carbon 5. As can also be seen from Figures 2 to 8, the gas filter layer 3 can have at least one layer 8 with ion exchangers ß, which is also referred to below as the ion exchange layer 8. In the ion exchange layer 8, no activated carbon 5 is present, or the proportion is very small compared to the ion exchanger 6.The gas filter layer 3 can therefore have at least one activated carbon layer 7 with activated carbon 5 and at least one ion exchange layer 8 with ion exchangers 6, which follow one another. At least one of the at least one ion exchange layer 8 and at least one of the at least one activated carbon layer 7 can be directly adjacent to one another, as can be seen from the exemplary embodiments in Figures 2 to 7. As can be seen from these figures, in these exemplary embodiments the activated carbon layers 7 and the ion exchange layers 8 are directly adjacent to one another. As can be seen from Figures 2 to 7, the gas filter layer 3 can consist of the at least one activated carbon layer 7 and the at least one ion exchange layer 8.

[0106] The gas filter layer 3, as shown in the embodiment of Figure 9, can also have a layer 10 comprising both activated carbon 5 and ion exchanger 6, which are expediently evenly / homogeneously distributed in the layer 10. This layer 10 is also referred to below as the mixed layer 10. In the embodiment shown in Figure 9, the gas filter layer 3 consists purely by way of example of the mixed layer 10.

[0107] As can be seen from Figure 8, the gas filter layer 3 can also have a layer 9 which is at least substantially free of activated carbon 5 and ion exchangers 6 and serves to store particles, in particular dust. This layer 9 is also referred to below as the dust storage layer 9. The dust storage layer 9 can, as can be seen from Figure 8, be arranged between an activated carbon layer 7 and an ion exchange layer 8. In the embodiment of Figure 8, the gas filter layer 3 consists of an activated carbon layer 7, the dust storage layer 9, and an ion exchange layer 8.

[0108] In the illustrated embodiments, the activated carbon 5 is present as particles 11, for example, as granules or powder (see Figure 2). These activated carbon particles 11 are also referred to below as activated carbon granules 11 for the sake of simplicity. Furthermore, the ion exchangers 6 in the illustrated embodiments are present as particles 12, for example, as granules or powder (see Figure 2). These ion exchange particles 12 are also referred to below as ion exchange granules 12 for the sake of simplicity.

[0109] In the embodiments shown, the respective activated carbon layer 7 has a grammage between 150 g / m 2 and 300 g / m 2 The activated carbon granules 11 can have a grain size of 20x40 or 30x60 or 35x60 or 20x50.

[0110] In the embodiments shown, the respective ion exchange layer 8 has a grammage between 200 g / m 2 and 270 g / m 2, especially 220 g / m 2 or 250 g / m 2 , on.

[0111] The activated carbon 5 can be present in either impregnated or unimpregnated form. As can be seen from the exemplary embodiments in Figures 2 to 4, the activated carbon 5 in the respective activated carbon layer 7 can consist predominantly of either impregnated activated carbon 5 or re-impregnated activated carbon 5. The respective activated carbon layer 7 with predominantly unimpregnated activated carbon 5 is also referred to below as unimpregnated activated carbon layer 13 for ease of differentiation. The respective activated carbon layer 7 with predominantly impregnated activated carbon 5 is also referred to below as impregnated activated carbon layer 14 for ease of differentiation.

[0112] In the illustrated embodiments, the activated carbon granules 11 and the ion exchange granules 12 are fixed / held in the gas filter layer 2 by means of an adhesive, for example, a polypropylene hotmelt (not shown). Likewise, the gas filter layer 3 can contain polymer fibers (not shown) that are melted to fix the activated carbon granules 11 and the ion exchange granules 12.

[0113] In the embodiment of Figure 2, the gas filter layer 3 is arranged between the carrier layer 4 and the particle filter layer 2. The carrier layer 4 is the foremost layer of the filter medium 1 along the flow path 104. In the embodiment shown, the gas filter layer 3 has two unimpregnated activated carbon layers 13 and an ion exchange layer 8. The two unimpregnated activated carbon layers 13 follow the carrier layer 4 along the flow path 104, thus being arranged downstream of the carrier layer 4. The ion exchange layer 8 follows the unimpregnated activated carbon layers 13, thus being arranged downstream of the unimpregnated activated carbon layers 13. The cathode supply air flows first through the carrier layer 4 and then successively through the unimpregnated activated carbon layers 13, then through the ion exchange layer 8 and then through the particle filter layer 2. The grammage of the carrier layer 4 can be between 55 g / m 2 and 75 g / m 2, for example 65 g / m 2 , In addition, the grammage of the respective unimpregnated activated carbon layer 13 can be between 240 g / m 2 and 260 g / m 2 , for example 250 g / m 2 The grammage of the ion exchange layer 8 can be between 210 g / m 2 and 230 g / m 2 , for example 220 g / m 2 The grammage of the particle filter layer 2 can be between 35 g / m 2 and 70 g / m 2 , for example 45 g / m 2 or 60 g / m 2 , amount to.

[0114] In the filter medium 1 in the embodiment of Figure 3, the gas filter layer 3 is arranged upstream of the carrier layer 4 and the particle filter layer 2 is arranged upstream of the gas filter layer 3. In this embodiment, the gas filter layer 3 has, purely by way of example, two activated carbon layers 7, namely an impregnated activated carbon layer 13 and an unimpregnated activated carbon layer 14, as well as an ion exchange layer 8. The ion exchange layer 8 follows the activated carbon layers 7 along the flow path 104. In the embodiment shown, the ion exchange layer 8 is thus arranged upstream of the particle filter layer 2 and the activated carbon layers 7 upstream of the ion exchange layer 8. The impregnated activated carbon layer 14 is arranged upstream of the unimpregnated activated carbon layer 13.

[0115] In the embodiment shown in Figure 4, the gas filter layer 3 has two activated carbon layers 7 and one ion exchange layer 8, wherein the ion exchange layer 8 follows the activated carbon layers 7 along the flow path 104. The ion exchange layer 8 is arranged upstream of the particle filter layer 2 in this embodiment. One of the activated carbon layers 7 is designed as an unimpregnated activated carbon layer 13 and is arranged upstream of the ion exchange layer 8. The other activated carbon layer 7 is designed as an impregnated activated carbon layer 14 and is arranged upstream of the unimpregnated activated carbon layer 13. The grammage of the carrier layer 4 can be between 55 g / m 2 and 75 g / m 2 , for example 65 g / m 2 The grammage of the impregnated activated carbon layer 14 can be between 150 g / m 2 and 170 g / m 2 , for example 160 g / m 2The grammage of the unimpregnated activated carbon layer 13 can be between 150 g / m 2 and 170 g / m 2 , for example 160 g / m 2 The grammage of the ion exchange layer 8 can be between 240 g / m 2 and 260 g / m 2 , for example 250 g / m 2 The grammage of the particle filter layer 2 can be between 30 g / m 2 and 50 g / m 2 , for example 40 g / m 2 , amount to.

[0116] In the embodiment shown in Figure 5, the gas filter layer 3 has an activated carbon layer 7 and an ion exchange layer 8. The ion exchange layer 8 follows the activated carbon layer 7 along the flow path 104. Thus, the ion exchange layer 8 is arranged upstream of the particle filter layer 2, the activated carbon layer 7 upstream of the ion exchange layer 8, and the carrier layer 4 upstream of the activated carbon layer 7.

[0117] In the exemplary embodiment of Figure 6, the gas filter layer 3 comprises two activated carbon layers 7 and an ion exchange layer 8, with the ion exchange layer 8 being arranged upstream of the activated carbon layers 7. The two activated carbon layers 7 are thus arranged one after the other upstream of the particle filter layer 2, and the ion exchange layer 8 is arranged upstream of the activated carbon layers 7. The carrier layer 4 is arranged upstream of the ion exchange layer 8.

[0118] Figure 7 shows an embodiment in which the gas filter layer 3 has two activated carbon layers 7 and an ion exchange layer 8 arranged between the activated carbon layers 7. In the embodiment shown in Figure 8, the gas filter layer 3 has the dust storage layer 9, as described above. In the embodiment shown, the dust storage layer 9 is arranged between an activated carbon layer 7 and an ion exchange layer 8. In the embodiment shown, the gas filter layer 3 has, purely by way of example, a single activated carbon layer 7 and a single ion exchange layer 8, wherein the activated carbon layer 7 is arranged upstream of the dust storage layer 9 and the ion exchange layer 8.Overall, the ion exchange layer 8 is arranged upstream of the particle filter layer 2, one of the activated carbon layers 7 is arranged upstream of the ion exchange layer 8, the dust storage layer 9 is arranged upstream of this activated carbon layer 7 and the other activated carbon layer 7 is arranged upstream of the dust storage layer 9.

[0119] In the embodiment shown in Figure 9, the gas filter layer 3 has only the mixed layer 10, thus corresponding to the mixed layer 10.

[0120] As shown in Figure 10, in the exemplary embodiments shown, at least the gas filter layer 3 is folded. Figure 11 shows an enlarged view of the section designated XI in Figure 10, wherein the filter medium 1 of the exemplary embodiment in Figure 2 is shown purely as an example. As can be seen from Figures 10 and 11, the layers 2, 3, 4 of the filter medium 1, in particular the entire filter medium 1, are preferably folded. The layers 2, 3, 4 thus form a so-called bellows 15. In the exemplary embodiment shown and preferably, the filter medium 1 is designed as a bellows 15. Here, as can be seen from Figure 10, the folding direction runs transversely to the flow direction 104, so that the layers 2, 3, 4 are flowed through one after the other (see Figure 11).

Claims

Claims 1 . Filter medium (1 ) for the cathode supply air of a fuel cell unit (102), - with a particle filter layer (2) for filtering particles from the cathode supply air, - with a gas filter layer (3) for removing harmful gases from the cathode supply air, which has activated carbon (5) and ion exchanger (6), - with a permeable carrier layer (4) for carrying the filter medium (1), - wherein the layers (2, 3, 4) follow one another and are connected to one another.

2. Filter medium according to claim 1, characterized in that the gas filter layer (3) is arranged between the particle filter layer (2) and the carrier layer (4) is arranged.

3. Filter medium according to claim 1 or 2, characterized in that the layers (2, 3, 4) are directly adjacent to one another.

4. Filter medium according to one of claims 1 to 3, characterized in that the gas filter layer (3) has at least one activated carbon layer (7) with activated carbon (5) and at least one ion exchange layer (8) with ion exchanger (6), which follow one another.

5. Filter medium according to claim 4, characterized in that at least one of the at least one ion exchange layer (8) is directly at least one of which borders at least one activated carbon layer (7).

6. Filter medium according to claim 4 or 5, characterized in that the gas filter layer (3) has two activated carbon layers (7) and an ion exchange layer (8), wherein the ion exchange layer (8) follows the activated carbon layers (7).

7. Filter medium according to claim one of claims 4 to 6, characterized in that the gas filter layer (3) has a dust storage layer (9) for storing particles, which is arranged in particular between at least one of the at least one activated carbon layers (7) and at least one of the at least one ion exchange layers (8).

8. Filter medium according to one of claims 4 to 7, characterized in that at least one of the at least one activated carbon layers (7) is designed as an unimpregnated activated carbon layer (13) with unimpregnated activated carbon (5).

9. Filter medium according to one of claims 1 to 8, characterized in that the gas filter layer (3) has at least one mixed layer (10) with Activated carbon granules (11) and ion exchange granules (12).

10. Filter medium according to one of claims 4 to 9, characterized in that at least one of the at least one activated carbon layers (7) has a grammage between 150 g / m 2 and 300 g / m 2 has.

11. Filter medium according to one of claims 4 to 10, characterized in that at least one of the at least one ion exchange layer (8) has a grammage between 200 g / m 2 and 270 g / m 2 , especially 220 g / m 2 or 250 g / m 2 , has.

12. Filter medium according to one of claims 1 to 9, characterized in that the particle filter layer (2) is designed to support the filter medium (1).

13. Filter medium according to one of claims 1 to 10, characterized in that the carrier layer (4) is designed to filter particles from the cathode supply air.

14. Filter medium according to one of claims 1 to 13, characterized in that the particle filter layer (2) has a grammage between 30 g / m 2 and 70 g / m 2 has.

15. Filter medium according to one of claims 1 to 14, characterized in that the particle filter layer (2) is a covering fleece with a grammage of maximum 50 g / m 2 has.

16. Filter medium according to one of claims 1 to 15, characterized in that the carrier layer (4) is a nonwoven layer with a grammage of at least 40 g / m 2 , especially between 40 g / m 2 and 100 g / m 2 , for example between 45 g / m 2 and 75 g / m 2 , has.

17. Filter medium according to one of claims 1 to 16, characterized in that the gas filter layer (3) is folded.

18. Filter medium according to claim 17, characterized in that the layers (2, 3, 4) are folded.

19. Filter medium according to claim 18, characterized in that the filter medium (1) is folded.

20. Fuel cell system (100), - with a fuel cell unit (102) which has at least one fuel cell (101), advantageously fuel cells (101) stacked on top of one another, - with a cathode gas supply system (103) for supplying the cathode supply air to at least one fuel cell (101), through which a flow path (104) of the cathode supply air leads, - with a filter device (107) which is arranged in the cathode gas supply system (103) upstream of the fuel cell unit (102) and has a filter medium (1) according to one of the preceding claims, wherein the flow path (104) leads through the filter medium (101).

21. Fuel cell system according to claim 20, characterized in that the particle filter layer (2) is arranged in the flow path (104) downstream of the gas filter layer (3) and the gas filter layer (3) is arranged downstream of the carrier layer (4).

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