EP4378012A1 - Fuel cell system and recirculation device for recirculating anode exhaust gas in a fuel cell system - Google Patents

Abstract

The invention relates to a recirculation device for recirculating anode exhaust gas in a fuel cell system, comprising a blower with a suction connection for connection to a fuel outlet of a fuel cell arrangement of the fuel cell system, a pressure connection for connection to a fuel cell inlet of the fuel cell arrangement, and an impeller for conveying the anode exhaust gas from the suction connection to the pressure connection. The recirculation device further comprises a turbine having an inlet for connection to a fuel tank of the fuel cell system, an outlet for connection to the fuel inlet of the fuel cell arrangement, and a turbine wheel kinematically coupled to the impeller of the blower, against which turbine wheel gaseous fuel from the fuel tank can flow through the inlet and which is rotatable in order to drive the impeller of the blower.

Description

Description

title

Fuel cell system and recirculation device for recirculation

Anode exhaust gas in a fuel cell system

technical field

The present invention relates to a fuel cell system and a recirculation device for recirculating anode exhaust gas in a fuel cell system.

State of the art

Fuel cells are increasingly used as energy converters, including in vehicles, to convert chemical energy stored in a fuel, such as hydrogen, directly into electrical energy together with oxygen. Fuel cells typically have an anode, a cathode, and an electrolytic membrane positioned between the anode and the cathode. The fuel is oxidized at the anode and the oxygen is reduced at the cathode. This creates water on the cathode side.

Typically, the anode of fuel cells is continuously supplied with excess gaseous fuel, that is, more fuel than would be stoichiometrically necessary for a given amount of oxygen supplied to the cathode. The excess fuel or the anode output is usually recirculated or fed back to the anode. This is typically done using a recirculation fan that circulates the anode exhaust from an outlet of the anode back to the inlet of the anode. The recirculation fan is usually operated by an electric motor. In order to improve the energy efficiency of a fuel cell system, DE 102007037096 A1 discloses driving the recirculation fan by means of a turbine. The turbine uses compressed air as the working fluid, which has been compressed by means of a compressor for supply to the cathode.

Disclosure of Invention

According to the invention, a recirculation device having the features of claim 1 and a fuel cell system having the features of claim 9 are provided.

According to a first aspect of the invention, a recirculation device for recirculating anode exhaust gas in a fuel cell system comprises a fan with a suction port for connection to a fuel outlet of a fuel cell arrangement of the fuel cell system, a pressure port for connection to a fuel inlet of the fuel cell arrangement and an impeller for conveying the anode exhaust gas from the suction port to the Pressure port and a turbine having an inlet for connection to a fuel tank of the fuel cell system, an outlet for connection to the fuel inlet

Fuel cell assembly and a kinematically coupled to the impeller of the fan turbine wheel, which can flow through the inlet with gaseous fuel from the fuel tank and is rotatable to drive the impeller of the fan.

According to a second aspect of the invention, a fuel cell system comprises a fuel cell arrangement having at least one fuel cell, a fuel inlet and a fuel outlet, and a recirculation device according to the first aspect of the invention, wherein the pressure port of the fan and the outlet of the turbine are connected to the fuel inlet, and wherein the The suction port of the blower is connected to the fuel outlet. One idea on which the invention is based is to partially break down the kinetic energy of a fuel flow that is supplied to the fuel cell system, for example from a tank, in a turbine and to drive a blower with the turbine in order to recirculate anode waste gas. For this purpose, according to the invention, an impeller of the turbine, which is driven by the fuel, such as hydrogen, and an impeller of the fan, which promotes the anode exhaust gas, are kinematically coupled to one another, for example via a shaft, a flange or by the turbine wheel and the impeller being in one piece are trained. Typically, the fuel is present in the tank at a pressure in a range between 8 bar and 20 bar and is supplied to an anode of the fuel cell assembly at a pressure in a range between 1.5 bar and 3.5 bar. The pressure difference can advantageously be reduced in the turbine and used to drive the fan.

By using the kinetic energy of a fuel flow that is supplied to the fuel cell system in a turbine to drive the fan that recirculates the anode exhaust gas, the energy efficiency of the fuel cell system is advantageously improved.

Advantageous refinements and developments result from the further dependent claims and from the description with reference to the figures of the drawing.

According to some embodiments, it can be provided that the turbine wheel has a circular outer circumference on which a plurality of essentially hemispherical flow surfaces are formed, with several nozzles being arranged along the outer circumference, which are oriented tangentially to the outer circumference and are each connected to the inlet. The flow surfaces can thus be concavely curved surfaces which extend hemispherically or essentially hemispherically. The nozzles are aligned so that the gaseous fuel is directed onto the airfoils, turning the fuel and causing the turbine wheel to move. Accordingly, the turbine can be designed as a type of free jet turbine. This advantageously results in a simpler structural design of the flow surfaces and an uncomplicated flow control.

According to some embodiments, it can be provided that the flow surfaces are defined by indentations formed in the outer circumference. The flow surfaces therefore do not protrude radially from the outer circumference, or only insignificantly, and a compact construction of the turbine is advantageously achieved.

According to some embodiments, it can be provided that the turbine wheel is attached to an outer circumference of the impeller of the fan. For example, the turbine wheel and the impeller of the fan can be formed as one piece, with an outer circumference of the impeller of the fan corresponding to the outer circumference of the turbine wheel. An even more compact construction of the recirculation device is thus realized.

According to some embodiments, it can be provided that the blower and the turbine have a common housing, with the blower being designed as a side channel compressor, with which the impeller of the blower has blades on one end face, which face a ring-segment-shaped side channel formed in the housing, wherein the suction port and the pressure port are formed in opposite end portions of the side duct, and wherein the housing has a mixing duct connected to an outlet port to which the outlet of the turbine and the pressure port of the fan are connected. Thus, the side passage in which the anode off-gas is conveyed and a space in which fresh fuel is supplied to the turbine are immediately adjacent with respect to the radial direction, and the fresh fuel and the anode off-gas are mixed directly within the common casing. This achieves an even more compact structure. The outer circumference of the impeller or of the turbine can be surrounded, for example, by a fresh gas channel in the form of a ring segment, into which the nozzles project at predetermined distances from one another. The fresh gas channel can open into the mixing channel. According to some embodiments, it can be provided that a gap is formed between the end face of the impeller of the fan and a region of the housing radially delimiting the side channel, which gap connects the side channel to a channel formed in the housing, so that liquid water can flow out of the side channel in the radial direction can be removed through the gap. The trough can be separated from the fresh gas duct, for example with respect to an axial direction. Optionally, the channel encloses the impeller or the turbine wheel at least partially and is preferably designed in the form of a ring segment. Due to the rotation of the impeller about an axis of rotation, the anode exhaust gas is accelerated in the radial direction, so that the water contained in the anode exhaust gas is transported radially outwards. The water can be discharged from the side channel in a simple manner through the gap.

According to some embodiments, it can be provided that the recirculation device has a drive device that is kinematically coupled to the impeller of the fan, in particular in the form of an electric motor. The flexibility of the regulation of the mass flow of fuel that is conveyed by the blower can thus be further increased.

According to some embodiments, it can be provided that the recirculation device has a collection container for collecting liquid water that is separated from the anode waste gas in the blower.

According to some embodiments, it can be provided that the collection container is connected to the blower by one or more lines, the line(s) and/or the collection container being thermally coupled to the drive device. For example, the drive can protrude into the collection container or the lines can or the lines can run along the drive device. This improves the cooling of the drive device and thus its service life.

According to some embodiments it can be provided that the pressure connection of the fan and the outlet of the turbine without intermediate ejector pump are connected directly to the fuel inlet. The combination of turbine and fan can advantageously provide the required recirculation mass flow and the required fresh gas mass flow both at high and at low loads, which simplifies the control of the fuel cell system. Furthermore, the flow losses in the system are reduced.

According to some specific embodiments, it can be provided that the fuel cell system has a metering valve connected to the inlet of the turbine, which can be connected to a fuel tank and is set up to vary a fuel mass flow supplied to the turbine from the fuel tank.

According to some embodiments, it can be provided that the fuel cell system has a tank which is connected to the inlet of the turbine.

The invention is explained below with reference to the figures of the drawings. From the figures show:

1 shows a schematic representation of a hydraulic circuit diagram of a fuel cell system according to an exemplary embodiment of the invention;

2 shows a plan view of a recirculation device according to an embodiment of the invention;

FIG. 3 is a simplified, fragmented, sectional view of the recirculation device shown in FIG. 2. FIG.

In the figures, the same reference symbols designate identical or functionally identical components, unless otherwise stated.

Fig. 1 shows an example and in a schematic way a fuel cell system 200. As shown in Fig. 1 by way of example, the fuel cell system 200 a tank 205, a fuel cell assembly 210, a recirculation device 100 and a flow control valve 220.

The tank 205 is designed to store gaseous fuel such as hydrogen at high pressure, for example at a pressure of more than 10 bar. The tank 205 is shown in FIG. 1 as part of the fuel cell system 200 purely by way of example. However, the invention is not limited to this, but the fuel cell system 200 can also be connectable to the tank 205 or another fuel source.

The fuel cell arrangement 210 can have a multiplicity of fuel cells 213 arranged to form a stack. In principle, however, it is also conceivable that only one fuel cell 213 is provided. As shown schematically in Fig. 1, each fuel cell 213 may have an anode 213A, a cathode 213B and an electrolyte 213C arranged therebetween, for example in the form of an electrolyte membrane.

The fuel cell arrangement 210 has a fuel inlet 211, via which the anode 213A can be supplied with gaseous fuel, e.g. hydrogen or natural gas, and a fuel outlet 212, via which unused or unreacted fuel can be removed from the anode 213A. Unconsumed fuel discharged at fuel outlet 212 may also be referred to as excess fuel or anode exhaust.

As also shown in Fig. 1, the fuel cell arrangement 210 has an oxygen inlet 214, via which the cathode 213B can be supplied with gaseous oxygen, either as pure oxygen or as oxygen contained in the ambient air, and a product outlet 215, via which unused or unused reacted oxygen and chemical reaction products, in particular water, can be discharged from the cathode 213B.

The fuel cell arrangement 210 is supplied with fuel from the tank 205 via a supply line 201 which is connected to the fuel inlet 211 . That at the fuel outlet 212 of the fuel cell assembly 210 exiting anode waste gas or the excess fuel is fed via a discharge line 202 of the recirculation device 100 recirculated by means of the recirculation device 100 and fed back to the fuel inlet together with fresh fuel.

As shown schematically in FIG. 1, the recirculation device 100 comprises a blower 1 and a turbine 2. Optionally, a drive device 4 and/or a collection container 5 can also be provided, as shown in FIG. 1 by way of example.

The blower 1 is only shown symbolically in FIG. 1 and has a suction connection 11 connected to the discharge line 202 and a pressure connection 12 connected to the supply line 201 . The fan 1 is designed to convey anode waste gas from the fuel outlet 212 to the fuel inlet 211 .

The turbine 2 is also shown only symbolically in FIG. 1 and has an inlet 21 which is connected to the tank 205 and an outlet 22 which is connected to the supply line 201 . As shown schematically in FIG. 1 , the turbine 2 is kinematically coupled to the fan 1 . The fuel, which is present at high pressure, can flow through the turbine 2 from the tank 205 and is designed to convert the kinetic energy stored in the flowing fuel and thereby to drive the fan 1 . Thus, the energy efficiency of the fuel cell system 200 can be improved in a simple manner since the energy requirement for driving the blower 1 is reduced. As is also shown schematically in FIG. 1 , the pressure connection 12 of the blower 1 and the outlet 12 of the turbine 2 can be connected directly to the fuel inlet 211 of the fuel cell arrangement, in particular without an interposed ejector pump. As a result, the fuel cell system 200 can be made more compact. However, it is not excluded that further flow components such as valves, humidifiers or dehumidifiers or the like are arranged between the pressure connection 12 of the blower 1 and the fuel inlet 211 or the outlet 12 of the turbine 2 and the fuel inlet 211 . The optional motor 4 can be an electric motor, for example, and is also kinematically coupled to the fan 1 in order to drive it at least in support of the turbine 2 .

For example, the flow control valve 220 may be located between the tank 205 and the inlet 21 of the turbine 2, as shown schematically in FIG. The flow control valve 220 can in particular be designed to vary a mass flow of fuel that is supplied to the turbine 2 .

FIG. 2 schematically shows a plan view of an exemplary recirculation device 100 as can be installed in the fuel cell system 200 shown in FIG. 1 . FIG. 3 shows a sectional view of the device 100 shown in FIG. As can also be seen in FIG. 2 , the blower 1 has an impeller 10 which can be rotated about an axis of rotation A1 for conveying the anode waste gas from the suction connection 11 to the pressure connection 12 . The turbine 2 has a turbine wheel 20, which can be flowed with and rotated by gaseous fuel from the fuel tank 205, for example about the same axis of rotation A1 as the impeller 10 of the fan 1. As is also shown schematically in Fig. 2, the recirculation device 100 can continue have a housing 3, the fan 1 and the turbine 2 preferably being housed together in the housing 3.

The blower 1 can in particular be designed as a side channel compressor, as is shown in FIGS. 2 and 3 is shown purely by way of example. The impeller 10 has a plurality of blades 13 on at least one or, as shown in FIG. 3 , on both axial end faces, which are distributed along the circumference of the impeller 10 . The blades 13 extend essentially along a radial direction RI, which is transverse to the axis of rotation A1. As in Figs. 2 and 3, the blades 13 can be arranged between an inner, with respect to the radial direction RI, annular support part 14 and with respect to the radial direction RI, an outer, annular shroud 15 extend. As indicated schematically by dashed lines in FIG. The blades 13 face the side channel 30, as can be seen in particular in FIG.

The impeller 10 of the fan 1 and the turbine wheel 20 are kinematically coupled to one another, so that the impeller 10 of the fan 1 can be driven by the turbine wheel 20 . In the figs. 2 and 3 it is shown purely by way of example that the impeller 10 and the turbine wheel 20 are designed as a common wheel. In particular, the turbine wheel 20 can be attached to an outer periphery 10a of the impeller 10 of the fan 1 . For example, the turbine wheel 20 can be formed by the shroud 15 of the impeller 10 of the fan 1, as is shown schematically in FIG. The outer circumference 10a of the impeller 10 and an outer circumference 20a of the turbine wheel 20 can thus both be formed by the shroud 15 . The turbine wheel 20 generally includes a plurality of airfoils 23a constructed and arranged to redirect flow impinging thereon such that momentum of the flow is converted into rotation of the turbine wheel 20 . For example, the flow surfaces 23a may be substantially hemispherical, as shown in FIG. In particular, two hemispherical flow surfaces 23a can be arranged next to one another along the longitudinal axis A1 and separated by a central web 26. As is also shown in FIG. 3, the flow surfaces 23a can be defined, for example, by indentations 23 formed in the outer periphery 20a. A plurality of flow surfaces 23a are provided along the outer circumference 20a of the turbine wheel 20 .

As shown schematically in FIG. 2 , a plurality of nozzles 24 which are each connected to the inlet 21 can be arranged along the outer circumference 20a of the turbine wheel 20 . 2 shows three nozzles 24 purely by way of example. A different number of nozzles can of course also be provided.

The nozzles 24 are oriented tangentially to the outer periphery 20a of the turbine wheel 20 to direct fuel onto the airfoils 23a. Thus will realized a kind of free jet turbine. As in Figs. 2 and 3, the housing 3 can have a fresh gas duct 35 which extends in the form of a ring segment along the outer circumference 20a of the turbine wheel 20 and into which the nozzles 24 protrude at predetermined intervals. The fresh gas channel 35 is open to the flow surfaces 23a. One end of the fresh gas duct 35 can form the outlet 22 of the turbine 2, for example. Furthermore, a supply channel 36 can be provided, which is connected to the inlet 21 and which is arranged outside of the fresh gas channel 35 with respect to the radial direction RI, as shown schematically in FIG. 2 . The nozzles 24 are connected to the supply channel 36 with an input. Furthermore, the supply channel 36 is connected to the fuel tank 205, for example via the flow control valve 220. In general, the flow control valve 220 can be attached, for example, to the housing 3 and thus together with the fan 1 and turbine

2 can be integrated into one unit, as shown in FIG. 2 by way of example.

As shown schematically in FIG. 2 , the housing 3 can have an outlet connection 32 which is provided for connection 32 to the supply line 201 or for connection to the fuel inlet 211 . The fresh gas duct 32 or the outlet 22 of the turbine 2 and the pressure port 12 of the fan 1 can each be connected to a mixing duct 31 which is connected to the outlet port 32 , as shown schematically in FIG. 2 .

As also shown in Fig. 3 by way of example and schematically, the housing

3 have a channel 34 which at least partially encloses the outer circumference 10a of the impeller 10 or the outer circumference 20a of the turbine wheel 20. As shown in FIG. 3, the channel 34 is separated from the fresh gas channel 35 along the axis of rotation A1 or in relation to the axial direction and is thus separated from the flow surfaces 23a. A channel 34 can be provided for each side channel 30 . In Fig. 3, therefore, two channels 34 are shown. As also shown in FIG. 3 , a gap 33 connecting the side channel 30 to the groove 34 can be formed between the end face of the impeller 10 of the fan 1 and a region of the housing 3 bordering the side channel 30 in the radial direction RI. When the impeller 10 is rotated around the axis of rotation Al, the anode off-gas in the side channel 30 becomes RI in the radial direction accelerated. Liquid water, which may be contained in the anode waste gas, is conveyed into the radially outer region of the side channel 30 due to its high density compared to the gaseous fuel as a result of the centrifugal force and can be transported through the gap 33 into the channel 34 . As in Figs. 1 to 3 indicated schematically, the

Gutter 34 are routed via one or more lines 51 into the collection container 5.

As shown purely schematically in Fig. 1, the optional drive device 4 can be thermally coupled to the collection container 5, e.g

Drive device 4 protrudes into the collection container 5. Alternatively or additionally, the lines 51 can also be thermally coupled to the drive device 4 . Although the present invention above with reference to

Exemplary embodiments was explained, it is not limited to this, but can be modified in many ways. In particular, combinations of the above exemplary embodiments are also conceivable.

Claims

Expectations 1. Recirculation device (100) for recirculating anode exhaust gas in a fuel cell system (200), comprising: a fan (1) with a suction connection (11) for connection to a fuel outlet (212) of a fuel cell arrangement (210) of the fuel cell system (200), a Pressure connection (12) for connection to a fuel inlet (211) of the fuel cell arrangement (210) and an impeller (10) for conveying the anode exhaust gas from the suction connection (11) to the pressure connection (12); and a turbine (2) having an inlet (21) for connection to a fuel tank (205) of the fuel cell system (200), an outlet (22) for connection to the fuel inlet (211) of the fuel cell assembly (210) and a kinematic connection to the impeller (10) of the fan (1) coupled turbine wheel (20), which through the inlet (21) with gaseous fuel from the fuel tank (205) can flow and rotate to drive the impeller (10) of the fan (1). 2. Recirculation device (100) according to claim 1, wherein the turbine wheel (20) has a circular outer periphery (20a) on which a plurality of substantially hemispherical flow surfaces (23a) are formed, and wherein along the outer periphery (20a) a plurality of nozzles ( 24) oriented tangentially to the outer periphery (20a) and each connected to the inlet (21). 3. Recirculation device (100) according to claim 2, wherein the flow surfaces (23a) are defined by indentations (23) formed in the outer periphery (20a). 4. recirculation device (100) according to claim 2 or 3, wherein the turbine wheel (20) is attached to an outer periphery (10a) of the impeller (10) of the fan (1). 5. recirculation device (100) according to claim 4, wherein the fan (1) and the turbine (2) have a common housing (3), wherein the fan (1) is designed as a side channel compressor, in which the impeller (10) of the fan (1) has blades (13) on one end face, which face a ring-segment-shaped side channel (30) formed in the housing (3), the suction connection (11) and the pressure connection (12) being formed in opposite end regions of the side channel (30). and wherein the housing (3) has a mixing duct (31) connected to an outlet port (32) to which the outlet (22) of the turbine (2) and the pressure port (12) of the fan (1) are connected. 6. Recirculation device (100) according to claim 5, wherein a gap (33) is formed between the end face of the impeller (10) of the blower (1) and a region of the housing (3) radially delimiting the side channel (30), which gap separates the side channel (30) connects to a groove (34) formed in the housing (3), so that liquid water can be discharged from the side channel (30) in the radial direction (RI) through the gap (33). 7. Recirculation device (100) according to one of the preceding claims, additionally comprising: a drive device (4) kinematically coupled to the impeller (10) of the fan (1), in particular in the form of an electric motor. The recirculation device (100) according to claim 7, further comprising: a collection tank (5) for collecting liquid water separated from the anode off-gas in the blower (1), the collection tank (5) communicating with the blower (1). one or more lines (51) is connected, and wherein the line (s) and / or the Collection container (5) is thermally coupled to the drive device (4). 9. Fuel cell system (200), comprising: a fuel cell assembly (210) having at least one fuel cell (213), a fuel inlet (211) and a fuel outlet (212); and a recirculation device (100) according to any one of the preceding claims; the pressure port (12) of the fan (1) and the outlet (12) of the turbine (2) being connected to the fuel inlet (211); and wherein the suction port (11) of the fan is connected to the fuel outlet (212). 10. Fuel cell system (200) according to claim 9, wherein the The pressure connection (12) of the blower (1) and the outlet (12) of the turbine (2) are connected directly to the fuel inlet (211) without an interposed ejector pump.