Recirculation device for a fuel cell

Abstract

The present invention relates to a recirculation device (2) for a fuel cell (3). The recirculation device (2) has a drive (10), a conveying means (20) and a separation means (30). The drive (10) comprises a drive shaft (11). The conveying means (20) is coupled to the drive shaft (11) in such a manner that the conveying means (20) can be driven by the drive (10). The conveying means (20) is designed to recirculate a medium as recirculated material in the fuel cell (3). The separation means (30) is arranged upstream of the conveying means (20) in the flow direction of the recirculated material. The separation means (30) is coupled to the drive shaft (11) in such a manner that the separation means (30) can be driven by the drive (10). The separation means (30) is designed to separate liquid from the recirculated material.

Description

[0001] Recirculation device for a fuel cell

[0002] The present invention relates to a recirculation device for a fuel cell. A corresponding method for recirculating a recirculated material in a fuel cell (recirculation method) is also disclosed.

[0003] In general, a fundamental development goal for fuel cells, especially for PEM (polymer electrolyte membrane) fuel cells, is to achieve the highest possible system efficiency of the fuel cell system.

[0004] A key lever for increasing system efficiency is the most efficient use of fuel (such as hydrogen) on the anode side. To ensure a good supply of catalyst layers in all areas of the fuel cell, the anode is typically operated superstoichiometrically (i.e., with a fuel surplus). This ensures that even areas near the anode outlet are still sufficiently supplied with fuel. However, releasing the resulting anode exhaust gas would cause significant losses, as it would release a large amount of unused fuel into the environment.

[0005] The British government published a study in April 2022 that found that hydrogen released into the atmosphere causes global warming eleven times faster than an equal amount of carbon dioxide.

[0006] Against this background, it is known to recirculate the anode exhaust gas. This can be done passively (e.g., by a jet pump) or actively (e.g., by a blower or compressor, hereinafter also referred to as a conveying device).

[0007] The high volume flow generated in this way in the fuel cell makes it possible, in principle, to layer a high stoichiometry on the catalyst and thus achieve even distribution without significant fuel losses. However, recirculation leads to an enrichment of reaction products (e.g., nitrogen and water) in the anode circuit. This has negative effects on the function of the fuel cell stack. A further disadvantage is that, when an active blower or compressor is used for recirculation, liquid components of the reaction products (e.g., water) in particular pose a challenge to the durability of the conveying system, as they can damage or erode it.

[0008] To counteract this, a separation device is installed in the anode recirculation path to remove excess liquids. This separation device represents an additional component in the overall system. It is associated with costs and increased installation space requirements. Currently available separation devices also cause pressure losses that must be compensated for by the conveying device, thus representing additional energy expenditure. Functionally, there is a conflict between these pressure losses and the separation efficiency of the existing concepts: the better the liquid separation, the higher the pressure losses.

[0009] A further challenge can be the inert gases (such as nitrogen) enriched in the recirculation. These are removed from the system by intermittently blowing off a fuel-inert gas mixture through a purge valve and replacing it with pure fuel.

[0010] To date, side-channel compressors and claw compressors have been used in series production conveying systems due to their robustness. Flow compressors offer fundamental advantages in terms of efficiency and space requirements, but are still in the development stage as a solution for anode recirculation.

[0011] The object of the present invention is therefore to increase the system efficiency of the fuel cell system, particularly in situations where space is limited. Further advantageous effects that can be achieved by the present invention include an increase in the service life of the components of the fuel cell system, in particular the delivery device, as well as a reduction in costs, pressure losses, and negative environmental impacts.

[0012] This object is achieved by a recirculation device or a fuel cell system having the features of the independent claims. Further advantageous embodiments of the present invention are the subject of the dependent claims.

[0013] According to the invention, a recirculation device for a fuel cell is provided. The recirculation device has a drive, a conveying device, and a separation device. The drive comprises a drive shaft. The conveying device is coupled to the drive shaft such that the conveying device can be driven by the drive. The conveying device is designed to recirculate a medium as recirculate in the fuel cell. The separation device is arranged upstream of the conveying device in the flow direction of the recirculate. The separation device is coupled to the drive shaft such that the separation device can be driven by the drive. The separation device is designed to separate liquid from the recirculate.

[0014] The fuel cell according to the invention can be any known type of fuel cell. However, the fuel cell is, in particular, a PEM fuel cell.

[0015] The fuel is preferably hydrogen, but other fuels may also be used.

[0016] The liquid is preferably water.

[0017] The medium or recirculate is an exhaust gas from the anode compartment of the fuel cell. The medium or recirculate is preferably a mixture containing hydrogen, nitrogen, and water. The water is present in liquid and gaseous form when exiting the anode of the fuel cell. Nevertheless, the term "exhaust gas" or "anode exhaust gas" is used in this disclosure, even if it contains liquids and is therefore not purely gaseous.

[0018] The drive is preferably an electric machine, more preferably an electric motor. However, any other drive device can also be used that can drive components of the recirculation device, such as the conveying device and the separation device, via a drive shaft (rotating shaft). For example, in a hybrid system that uses an internal combustion engine in addition to the fuel cell system, it is also possible to use the internal combustion engine as the drive. In this case, a rotational force is transmitted to the drive shaft by means of a transmission device (for example, a belt), which in turn can drive the conveying device and the separation device. Other drives, such as a turbine operating with exhaust gas, are also conceivable.

[0019] The conveying device is preferably a flow compressor. An axial or radial compressor can be used.

[0020] The conveying device is preferably configured to recirculate the exhaust gas to the anode chamber of the fuel cell via a recirculation path in order to convert unused fuel, preferably hydrogen, in the fuel cell. This increases the efficiency of the fuel cell. However, it would also be conceivable to use the recirculation device on the cathode side of the fuel cell. In this case, "fuel" refers to the oxidizing agent that is converted in the fuel cell. A preferred oxidizing agent is oxygen, preferably from the ambient air.

[0021] The separation device is preferably a centrifuge. In other words, the separation device separates liquid by conveying the liquid in the recirculate radially outward due to centrifugal forces through a rotation applied by the drive shaft, thus separating it from the lighter gaseous components of the recirculate, which remain radially further inward. Even more preferably, the separation device is a centrifuge that can be mounted on the drive shaft together with the conveying device. The separation device according to the invention is, in particular, not a stationary device that separates liquid, for example, by means of impacting recirculate. In other words, separation devices that do not rotate with the drive shaft are not separation devices within the meaning of the present disclosure or invention.

[0022] Unless otherwise described in this disclosure, the terms “axial” and “radial” refer to the drive shaft.

[0023] The drive shaft can be solid or hollow. It can consist of several, for example, two or three, concentrically arranged shafts. This can be used, for example, in multi-stage compressors as conveying devices and in multi-stage turbines as drives. It is also conceivable to drive a multi-stage compressor as a conveying device with more than one electric motor at different speeds via more than one drive shaft.

[0024] Unless otherwise stated, the terms "downstream" and "upstream" in this disclosure refer to the main flow direction of the medium from the anode outlet to the anode inlet. Therefore, the recirculation direction is generally decisive.

[0025] The coupling of the conveyor devices and / or the separation device to the drive shaft is preferably achieved by directly placing and non-rotatably connecting the device to and with the drive shaft. For example, shrink fits or splines are conceivable.

[0026] Preferably, the conveying device is arranged at a first axial end of the drive shaft. In this embodiment, the separation device is arranged at a second axial end of the drive shaft, which is opposite the first axial end. The drive can more preferably be arranged between the conveying device and the separation device on the drive shaft. Alternatively, both the conveying device and the separation device are arranged at the same first axial end of the drive shaft. In this embodiment, either the conveying device or the separation device can be arranged further outwards in the axial direction, i.e. closer to the first axial end. In this embodiment, the drive is arranged at a second axial end of the drive shaft, which is opposite the first axial end.

[0027] The designs described ensure, on the one hand, a compact design and, on the other hand, the power transmission required for driving.

[0028] In a preferred embodiment, the separation device is an impeller mounted on the drive shaft. The impeller has at least one inlet for the recirculated material and at least two outlets spaced radially from the impeller. Thus, liquid components of the recirculated material can exit the impeller from a radially outer outlet. Gaseous components of the recirculated material can exit the impeller from a radially inner outlet. This arrangement achieves the separation effect.

[0029] Even more preferably, the inlet and the radially inner outlet are arranged closer to the second axial end of the drive shaft than the radially outer outlet, which is arranged further toward the first axial end of the drive shaft. This applies to cases where the separation device is arranged at the second axial end of the drive shaft or is at least arranged closer to the second axial end than the conveying device (for example, when the separation device is arranged at the first axial end, but the conveying device is arranged further toward the first axial end than the separation device).In the embodiment in which the separation device is arranged at the first axial end of the drive shaft and the conveying device is arranged further in the direction of the second axial end than the separation device, the inlet and the radially inner outlet are arranged closer to the first axial end of the drive shaft than the radially outer outlet arranged further in the direction of the second axial end of the drive shaft. Generally, when the separation device is designed as an impeller mounted on the drive shaft, the inlet and the radially inner outlet are arranged further on the side of the separation device opposite the conveying device than the radially outer outlet arranged further in the direction of the conveying device. Even more preferably, the inlet and the radially inner outlet are arranged directly at the axial end of the drive shaft.

[0030] Alternatively or additionally, the inlet and the radially inner outlet are arranged at one end of a channel in the impeller, and the radially outer outlet is arranged at another end of the channel in the direction of flow of the recirculated material in the impeller. The inlet and the radially inner outlet are separated by a partition wall in the channel. The partition wall divides the channel into two sub-channels, at least in the region of one end of the channel.

[0031] As an alternative to the impeller design, the separation device has two housings. One housing is an inner housing mounted on the drive shaft and rotatable with it. The other housing is a stationary outer housing arranged around the inner housing. The inner housing has at least one first opening as an axial inlet, which penetrates a first axial housing wall, at least one second opening as an axial outlet, which penetrates a second axial housing wall, and at least one third opening as a radial outlet, which penetrates a radial housing wall.The outer housing has at least one fourth opening as an axial inlet, which penetrates a first axial housing wall, at least one fifth opening as an axial outlet, which penetrates a second axial housing wall, and at least one sixth opening as a radial outlet, which penetrates a radial housing wall and, in the properly installed state of the recirculation device, is arranged below the inlets and outlets of the inner and outer housing. The properly installed state of the recirculation device is a state in which the recirculation device is installed in the fuel cell system for normal operation. The sixth opening, which penetrates the radial housing wall of the outer housing, is preferably arranged at or directly in the region of a lowest point of the outer housing in the properly installed state of the recirculation device.

[0032] The inner housing is preferably a rotationally symmetrical housing, and more preferably a drum. Even more preferably, the drum is a screening drum.

[0033] Alternatively or additionally, the axial inlets of the inner and outer housings (the first and fourth openings) are arranged on the same first axial side of the separation device and the axial outlets of the inner and outer housings (the second and fifth openings) are arranged on the same second axial side of the separation device, which is opposite to the first axial side of the separation device.

[0034] Alternatively or additionally, the inner and outer housings are arranged coaxially around the drive shaft.

[0035] Alternatively or additionally, the lower part of the outer housing in the properly installed state of the recirculation device is funnel-shaped.

[0036] Alternatively or additionally, at least one of the axial inlets and outlets of the inner and outer housings (first, second, fourth, and / or fifth openings) is formed by a drive shaft opening of the inner and / or outer housing. The drive shaft opening of the housings is the opening through which the drive shaft is inserted.

[0037] In a preferred embodiment, the recirculation device has a purge valve arranged downstream of the separation device in the flow direction of the recirculate in the recirculation path. The purge valve is configured to periodically expel inert gaseous components of the recirculate from the recirculation path. The inert gaseous components of the recirculate are preferably nitrogen or nitrogen mixtures. In a preferred embodiment, the conveying device and the separation device are designed as an integrated assembly of the recirculation device, which can be installed as a single unit in the recirculation device and removed from the recirculation device. In other words, the recirculation device is modular in design, such that one of its modules represents a combination of conveying device and separation device.The module, which comprises the conveying device and separation device, is assembled or disassembled as a whole during the initial assembly of the recirculation device as well as during repair work on the recirculation device, without being further disassembled into the individual components of the conveying device and separation device.

[0038] The fuel cell system according to the invention comprises the recirculation device described above with all preferred embodiments.

[0039] In the fuel cell system, the fuel cell is preferably a polymer electrolyte membrane fuel cell.

[0040] Alternatively or additionally, the fuel cell in the fuel cell system is operated over-stoichiometrically.

[0041] The inventive (system) integration of conveyor and separation device has the following advantages:

[0042] Elimination of a separate separation device (package advantage)

[0043] Higher separation efficiency than with a static separation system due to the high centrifugal forces

[0044] Ensuring that no liquid water components are added to the conveying system

[0045] Minimizing the risk of erosion by water droplets on the flow compressor wheel

[0046] Extending the service life of the conveying system. Furthermore, the liquid separators and recirculation devices described here are robust, cost-effective, and more efficient than standard liquid separator components in conventional fuel cell systems.

[0047] All features described above and below can be combined with each other as long as the combination is technically possible and advantageous.

[0048] Further details and advantages of the present invention will become apparent from the following description of the exemplary preferred embodiments.

[0049] Fig. 1 shows a schematic view of the fuel cell system according to the invention.

[0050] Fig. 2 shows schematically a recirculation device according to the invention.

[0051] Fig. 3 shows schematically and in a partial sectional view a part of the recirculation device according to the invention, in which the separation device is designed as an impeller mounted on the drive shaft.

[0052] Fig. 4 shows schematically and in a partial sectional view a part of the recirculation device according to the invention as an alternative to the recirculation device shown in Fig. 3, in which the separation device is designed as a screening drum placed on the drive shaft with a coaxially arranged stationary outer housing.

[0053] Fig. 5 shows schematically a recirculation device according to the invention as an alternative to the recirculation device shown in Fig. 2.

[0054] In the following, identical parts are designated by the same reference numerals.

[0055] The fuel cell system 1 according to the invention is shown in Fig. 1. The

[0056] Fuel cell system 1 comprises a fuel cell 3 and a recirculation device 2 for the fuel cell 3. The fuel cell 3 has an anode chamber 4 on the anode side (left of the fuel cell 3 in the illustration of Fig. 1) and a cathode chamber on the cathode side (right of the fuel cell 3 in the illustration of Fig. 1).

[0057] The cathode side of fuel cell 3 comprises a turbine-driven compressor, a cooling device, an evaporation device, and a liquid separator (water separator). The cathode side of fuel cell 3 serves to supply and preferably recirculate the oxidizing agent (oxygen) from and to fuel cell 3. The cathode side of fuel cell 3 shown here represents a conventional cathode side of a known fuel cell.

[0058] The anode side of the fuel cell 3 comprises the integrated assembly 100 consisting of the conveyor device 20 and the deposition device 30, which is arranged between the anode outlet and the anode inlet. As shown schematically in Fig. 1, the conveyor device 20 and the deposition device 30 constitute a single component of the fuel cell system 1.

[0059] A purge valve 90 is arranged downstream of the assembly 100 comprising the conveying device 20 and the separation device 30. This purge valve 90 allows inert gases, such as gaseous nitrogen, contained in the recirculate from the fuel cell 3 (more precisely, from the anode chamber 4) and separated from the liquid portions of the recirculate in the separation device 30, to be expelled from the fuel cell system 1. The expelled inert gases are then replaced with fuel (hydrogen) to optimize the processes in the fuel cell and increase its efficiency and effectiveness.

[0060] In Fig. 1, a further valve (in the figure above the purge valve 90) is also shown upstream of the assembly 100 in the supply path of the anode chamber 4, which serves as a supply valve and doses and / or shuts off the fuel supplied from a fuel reservoir (pressure vessel not shown) or allows it to pass to the anode chamber 4.

[0061] Fig. 2 schematically shows the arrangement of the components in the assembly 100. The drive 10 for the recirculation device 2 is, for example, an electric motor (electric machine). The electric motor 10 has a rotating shaft which outputs the torque generated by the electric motor 10 and thus functions as a drive shaft 11.

[0062] A conveying device 20 in the form of a flow compressor is arranged at a first (left in the figure) axial end of the drive shaft 11. A separation device 30 in the form of a water separator is arranged at a second (right in the figure) axial end of the drive shaft 11, opposite the first axial end.

[0063] In the present example, the flow compressor 20 and the water separator 30 are both mounted directly on the drive shaft 11 and are connected to the drive shaft 11 in a rotationally fixed manner. Another type of coupling to the drive shaft 11, such as an indirect connection via a drive force-transmitting element such as a gear, is also possible.

[0064] As indicated by an arrow in Fig. 2, an anode exhaust gas flows out of the anode outlet of the anode chamber 4 and into the water separator 30. The anode exhaust gas is a mixture of excess hydrogen, nitrogen, and water, which is present in liquid and gaseous form.

[0065] If the liquid water hits the flow compressor 20, it can cause short-term damage and long-term erosion. Therefore, the water separator 30 is installed upstream of the flow compressor 20 to remove the liquid water components from the anode exhaust gas.

[0066] Accordingly, liquid water flows out of the water separator 30 at a liquid outlet and is discharged from the fuel cell system 1, and a gas mixture of hydrogen, nitrogen and water vapor flows out of the water separator 30.

[0067] Preferably, the inert gas nitrogen is vented via the purge valve 90 and replaced with additional hydrogen from the pressure vessel. The gas mixture then flows to the flow compressor 20, where it is compressed and fed to the anode chamber 4 via the anode inlet.

[0068] The design shown makes it possible to drive the flow compressor 20 and the water separator 30 by the same drive 10 with an overall very compact and preferably integrated arrangement.

[0069] Fig. 3 shows a preferred embodiment of the liquid separator (water separator) 30. The embodiment in Fig. 3 is very compact and consists of few individual parts.

[0070] In the embodiment shown in Fig. 3, the water separator 30 is an impeller (vane) 40 which is mounted on the drive shaft 11 of the electric motor 10 and is connected thereto in a rotationally fixed manner and therefore rotates therewith.

[0071] The impeller 40 has an axial portion that rests on the drive shaft 11 and a radial portion that extends radially outward from the axial portion. In other words, the impeller 40 is substantially L-shaped.

[0072] In the embodiment shown, the impeller 40 has an inlet 41 for the recirculate (anode exhaust gas), which leads to a channel 44. The channel 44 is divided into two sub-channels 45 and 46 by a partition 47. The partition 47 ensures that the liquid water cannot flow back into the gas stream and that the inlet flow is separated from the outlet flow. The sub-channel 45 is connected to the inlet 41. The channel 44 and the partition 47 are designed such that they run radially outwards along their axial path. In other words, the channel 44 and the partition 47 move radially further and further away from the drive shaft 11 along their axial path. In other words, the channel 44 and the partition 47 essentially have an L-shape.At the end of the dividing wall 47 in the channel 44 there is preferably a space in which the liquid water collects at the radially outer end due to the centrifugal forces generated by high rotational speeds. The liquid water is then conveyed outwards via the radially outer outlet 42 and thus separated from the recirculation. The lighter gaseous components of the recirculation are not conveyed all the way outwards in the radial direction, flow around the end of the dividing wall 47 and flow further into the partial channel 46 in the direction of the outlet 43. This is arranged further inwards in the radial direction than the outlet 42. In the embodiment shown, it is also formed near the inlet 41 and separated from it by the dividing wall 47. The gaseous recirculation flows out of the outlet 43 and contains hydrogen, nitrogen and water vapor and preferably no or at least negligible amounts of liquid water.

[0073] In the embodiment shown in Fig. 3, the flow compressor would be arranged at the other end of the drive shaft 11 than the impeller 40 (left in the figure), but is not shown here for reasons of illustration.

[0074] Fig. 4 shows a preferred embodiment of the liquid separator (water separator) 30.

[0075] In the embodiment shown in Fig. 4, the water separator 30 comprises a screening drum (inner housing) 60, which is mounted on the drive shaft 11 of the electric motor 10 and is non-rotatably connected thereto, thus rotating with it. The screening drum 60 is surrounded by an outer housing 70. The outer housing 70 is stationary, meaning that it does not rotate with the screening drum 60 or the drive shaft 11.

[0076] In the preferred embodiment shown, the outer housing 70 is a separate housing provided specifically for the water separator 30. However, it is also conceivable that the outer housing 70 is the housing of the assembly 100. In other words, if at least a portion of the housing of the assembly 100 fulfills the function of collecting the liquid water radially propelled outward by the screening drum 60 and (preferably by means of gravity) draining it from the water separator 30, as well as passing the gaseous components of the recirculated water to the flow compressor 30, this portion of the housing or the housing of the assembly 100 represents the outer housing 70. It is also conceivable that the outer housing 70 is only partially provided separately and, for example, assumes the function of collecting the water, while, for example, the drainage of the water (preferably by means of a funnel-shaped section) is assumed by the housing of the assembly 100.In this case, the partially provided outer housing 70 and the housing of the assembly 100 would be the outer housing according to the invention.

[0077] In the embodiment shown in Fig. 4, the screening drum 60 and the outer housing 70 are arranged coaxially around the drive shaft 11, with the screening drum 60 surrounding the drive shaft 11 and the outer housing 70 surrounding the screening drum 60. The coaxial arrangement results in the recirculation flowing without deflection, thereby reducing pressure losses. The drive shaft extends through drive shaft openings in the axial housing walls 64, 65, 74, and 75 (end faces) of the screening drum 60 and the outer housing 70. The two drive shaft openings of the screening drum 60 and the outer housing 70, arranged axially next to one another on one axial side (right in the figure), are simultaneously the inlets of the screening drum 60 and the outer housing 70 for the recirculation (more precisely, they are simultaneously the first and fourth openings 61, 71).The two drive shaft openings of the screening drum 60 and the outer housing 70 arranged axially next to each other on the other (left in the figure) axial side are simultaneously the outlets of the screening drum 60 and the outer housing 70 for the (gaseous) recirculate (more precisely, they are simultaneously the second and fifth openings 62, 72).

[0078] The recirculate enters the water separator 30 through the (first and fourth) openings 71 and 61 and is swirled by the rotation of the screen drum 60, which is shown by a spiral line in Fig. 4. However, the gaseous portions of the recirculate remain largely in the radially inner region of the screen drum 60 and exit the water separator 30 through the (second and fifth) openings 62 and 72.

[0079] In the embodiment shown in Fig. 4, the screening drum 60 has a plurality of (third) openings 63 that penetrate the radial housing wall 66 of the screening drum 60 and through which liquid water from the recirculate exits the screening drum 60 radially outward due to the centrifugal forces generated by the rotation of the screening drum 60. The water impacts the walls of the outer housing 70 and flows downward due to gravity. The liquid water can then flow out of the water separator 30 through the (sixth) opening 73 that penetrates the radial housing wall 76 of the outer housing 70. Since the water separator 30 is installed or mounted as intended in the fuel cell system 1 in the orientation shown in Fig. 4, the liquid water also flows downward there. The drainage of water can be facilitated by a funnel-shaped part 77 of the outer housing 70.The funnel-shaped part 77 is located at the lower end of the outer housing 70.

[0080] The outer housing 70 can have at least one (seventh) opening in the radial housing wall, preferably in the region above the drive shaft 11, through which the gaseous components of the recirculate can exit the water separator 30. The two streams from the outlets formed by the second and fifth openings 62, 72 and the seventh opening can be combined downstream of the water separator 30 and, preferably after the nitrogen has been vented by means of the purge valve and replaced with additional hydrogen, can be fed to the flow compressor 20.

[0081] In the embodiment shown in Fig. 4, the flow compressor would be arranged at the other end of the drive shaft 11 than that of the water separator 30 (left in the figure), but is not shown here for reasons of illustration.

[0082] Fig. 5 corresponds to the representation in Fig. 2 and is an alternative embodiment to the embodiment shown in Fig. 2.

[0083] In Fig. 5, both the flow compressor 20 and the water separator 30 are arranged at the same (first) axial end of the drive shaft 11. The electric motor 10 is arranged at the other (second) axial end of the drive shaft 11.

[0084] In the embodiment shown in Fig. 5, the water separator 30 is arranged closer to the (first) axial end of the drive shaft 11 than the flow compressor 20. In other words, the flow compressor 20 is arranged in the axial direction between the water separator 30 and the electric motor 10. As shown in Fig. 5 by arrows, the flow compressor 20 is also arranged downstream of the water separator 30 in the flow direction of the recirculated fluid in this embodiment.

[0085] The present invention also encompasses an embodiment (not shown in the figures) similar to that shown in Fig. 5, in which the positions of the flow compressor 20 and the water separator 30 are reversed. In other words, in this embodiment, the flow compressor 20 is arranged closer to the (first) axial end of the drive shaft 11 than the water separator 30. In other words, the water separator 30 is arranged in the axial direction between the flow compressor 20 and the electric motor 10. The routing of the recirculate is selected such that the flow compressor 20 is also arranged downstream of the water separator 30 in this embodiment.

[0086] It is understood that in the embodiments of Figures 2 and 5 as well as the above-described modification of Figure 5 with swapped positions of the flow compressor 20 and the water separator 30, the water separators 30 shown in Figures 3 and 4 (as impeller 40 or as screen drum 60 surrounded by a stationary outer housing 70) are used.

Claims

AMENDED CLAIMS received by the International Bureau on 5 December 2024 (05.12.2024) 1. Recirculation device (2) for a fuel cell (3), comprising a drive (10) comprising a drive shaft (11); a conveying device (20) coupled to the drive shaft (11) such that the conveying device (20) can be driven by the drive (10), and configured to recirculate a medium as recirculate in the fuel cell (3);and a separation device (30) arranged upstream of the conveying device (20) in the flow direction of the recirculate, which is coupled to the drive shaft (11) in such a way that the separation device (30) can be driven by the drive (10) and which is designed to separate liquid from the recirculate, wherein the separation device (30) is a centrifuge which is an impeller (40) placed on the drive shaft (11), which has at least one inlet (41) for the recirculate and at least two outlets (42, 43) spaced apart in the radial direction of the impeller (40), so that liquid portions of the recirculate can exit the impeller (40) from a radially outwardly located outlet (42) and gaseous portions of the recirculate can exit the impeller (40) from a radially inwardly located outlet (43).

2. Recirculation device (2) according to claim 1, wherein the inlet (41) and the radially inwardly extending outlet (43) are arranged further on the side of the separation device (30) opposite the conveying device (20) than the radially outwardly extending outlet (42) arranged further in the direction of the conveying device (20), and are preferably arranged directly at the axial end of the drive shaft (11); and / or the inlet (41) and the radially inner outlet (43) are arranged at one end of a channel (44) in the impeller (40) and the radially outer outlet (42) is arranged at another end of the channel (44) in the flow direction of the recirculate in the impeller (40), wherein the inlet (41) and the radially inner outlet (43) are separated by a partition wall (47) in the channel (44), which divides the channel (44) into two sub-channels (45, 46) at least in the region of one end of the channel (44). 22 AMENDED SHEET (ARTICLE 19) 3. Recirculation device (2) for a fuel cell (3), comprising a drive (10) comprising a drive shaft (11); a conveying device (20) coupled to the drive shaft (11) such that the conveying device (20) can be driven by the drive (10), and configured to recirculate a medium as recirculate in the fuel cell (3); and a separation device (30) arranged upstream of the conveying device (20) in the flow direction of the recirculate, which is coupled to the drive shaft (11) in such a way that the separation device (30) can be driven by the drive (10) and which is designed to separate liquid from the recirculate, wherein the separation device (30) is a centrifuge having an inner housing (60) placed on the drive shaft (11) and rotatable therewith, and a stationary outer housing (70) arranged around the inner housing (60),the inner housing (60) has at least one opening (61) as an axial inlet, which penetrates a first axial housing wall (64), at least one opening (62) as an axial outlet, which penetrates a second axial housing wall (65), and at least one opening (63) as a radial outlet, which penetrates a radial housing wall (66), and the outer housing (70) has at least one opening (71) as an axial inlet, which penetrates a first axial housing wall (74), at least one opening (72) as an axial outlet, which penetrates a second axial housing wall (75), and at least one opening (73) as a radial outlet, which penetrates a radial housing wall (76), and is arranged below the inlets and outlets of the inner and outer housings (60, 70) in the properly assembled state of the recirculation device (2).

4. Recirculation device (2) according to claim 3, wherein the opening (73) is arranged as a radial outlet at or directly in the region of a lowest point of the outer housing (70).

5. Recirculation device (2) according to claim 3 or 4, wherein the inner housing (60) is a rotationally symmetrical housing and preferably a drum, more preferably a screening drum; and / or 23 AMENDED SHEET (ARTICLE 19) the axial inlets of the inner and outer housings (70) are arranged on the same first axial side of the separation device (30), and the axial outlets of the inner and outer housings (70) are arranged on the same second axial side of the separation device (30); and / or the inner and outer housings (70) are arranged coaxially to one another around the drive shaft (11); and / or the lower part (77) of the outer housing (70) is funnel-shaped when the recirculation device (2) is in the properly assembled state; and / or at least one of the axial inlets and outlets of the inner and outer housings (60, 70) is formed by a drive shaft opening of the inner and / or outer housing (70), through which the drive shaft (11) is inserted.

6. Recirculation device (2) according to one of the preceding claims, wherein the recirculate is an exhaust gas from an anode chamber (4) of the fuel cell (3) and / or the liquid is water; and the conveying device (20) is configured to resupply the exhaust gas to the anode chamber (4) via a recirculation path in order to convert unused fuel, preferably hydrogen, in the fuel cell (3).

7. Recirculation device (2) according to one of the preceding claims, wherein the conveying device (20) is a flow compressor; and / or the drive (10) is an electric machine; and / or the conveying device (20) is arranged at a first axial end of the drive shaft (11), the separation device (30) is arranged at an opposite second axial end of the drive shaft (11), and the drive (10) is preferably arranged between the conveying device (20) and the separation device (30) on the drive shaft (11); or the conveying device (20) and the separation device (30) are arranged at a first axial end of the drive shaft (11), wherein the conveying device (20) or the separation device (30) is arranged closer to the first axial end, and the drive (10) is arranged at an opposite second axial end of the drive shaft (11). 24 AMENDED SHEET (ARTICLE 19) 8. Recirculation device (2) according to one of the preceding claims, further comprising a flushing valve (90) arranged downstream of the separation device (30) in the Flow direction of the recirculate is arranged in the recirculation path and is designed to periodically expel inert gaseous components, preferably nitrogen or nitrogen mixtures, of the recirculate from the recirculation path.

9. Recirculation device (2) according to one of the preceding claims, wherein the conveying device (20) and the separation device (30) are designed as an integrated assembly (100) of the recirculation device (2), which is intended to be mounted as a single unit in the recirculation device (2) and dismountable from the recirculation device (2).

10. Fuel cell system (1) with a recirculation device (2) according to one of the preceding claims, wherein the fuel cell (3) preferably has a polymer electrolyte Membrane fuel cell and / or a superstoichiometric fuel cell (3). 25 AMENDED SHEET (ARTICLE 19)

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