WO2013152836A1

WO2013152836A1 - Anode circuit for a fuel cell

Info

Publication number: WO2013152836A1
Application number: PCT/EP2013/000963
Authority: WO
Inventors: Gerald Hornburg; Massimo Venturi
Original assignee: Daimler Ag
Priority date: 2012-04-12
Filing date: 2013-03-30
Publication date: 2013-10-17
Also published as: DE102012007384A1

Abstract

The invention relates to an anode circuit (12) for a fuel cell (3), comprising a recirculation line (10), which connects an output of an anode chamber (4) of the fuel cell (3) to an input of the anode chamber (4) of the fuel cell (3), and comprising a recirculation conveyor (11). The invention is characterised in that a valve device (15) for stopping a flow through the recirculation line (10) is arranged in the recirculation conveyor (10).

Description

Anode circuit for a fuel cell

The invention relates to an anode circuit for a fuel cell, according to the

In addition, the invention relates to a method for starting a fuel cell system with such a

Anode circuit. Finally, the invention also relates to the use of the

Anodenkreislaufs or a method for starting a fuel cell system with such an anode circuit.

Fuel cell systems are known from the general state of the art. They can be used in particular in vehicles for generating electrical power, for example for generating electrical drive power. Under vehicles in the context of the invention, all rail-bound or trackless land vehicles with driver or with an autonomous driving system can be understood. Likewise, watercraft or aircraft may be considered as vehicles, in particular in aircraft, in addition to the provision of electrical drive power, here in particular the generation of electrical power for an electrical system of the vehicle is in the foreground.

Such fuel cell systems often have low-temperature fuel cells in the form of so-called PEM fuel cells with proton exchange membranes. The fuel cell itself then typically consists of a plurality of individual PEM cells, which are stacked in the fuel cell to form a so-called fuel cell stack or stack. The fuel cell stack or fuel cell stack has an anode space and a cathode space. The cathode space is typically supplied with air or an oxygen-containing medium, the anode space with hydrogen or a hydrogen-containing medium. Now it is so that to the maximum Exploitation of the available active area of the fuel cell in the area of the fuel cell

Anode space a so-called anode circuit is known from the general state of the art. Such an anode circuit for a fuel cell comprises a

Rezirkulationsleitung which connects an output of the anode compartment of the fuel cell to the input of the anode compartment of the fuel cell, and which

typically has a recirculation conveyor. Through the anode circuit, an excess of fuel can be used, as unused exhaust gas from the anode compartment of the fuel cell via the recirculation conveyor is transported back into the anode compartment of the fuel cell. The anode compartment of the fuel cell is then typically supplied mixed with fresh fuel. This results in a comparatively large volume flow of fuel through the anode compartment. The available active area of the fuel cell is thus ideally utilized and resulting product water is well discharged from the anode space by the comparatively large volume flow.

Now it is the case that in certain operating situations of the fuel cell or a fuel cell equipped with the fuel cell system, a recirculation is not desired because, for example, during cold start of the fuel cell system by the anode circuit and the recirculated exhaust gas comparatively much from the fuel cell already discharged moisture or condensed moisture back in the

Anodenraum is registered. It can also be at a start at

At sub-freezing ambient temperatures, ice formation occurs in the supply of recirculated exhaust gas and fresh fuel mixed with it, which would delay the start of the fuel cell. These aspects are a serious disadvantage for the cold start of a fuel cell with an anode circuit.

In order to counteract this problem, it is known from DE 10 2007 057 451 A1 to provide a bypass line around a metering unit designed, for example, as a gas jet pump and thus as a recirculation conveyor, in order to bypass this gas jet pump in the cold start case, for example if it is frozen in the region of its nozzle. Inevitably, this also results in a prevention of recirculation, which can also be partially avoided the disadvantages mentioned above. However, the problem with the structure described in DE 10 2007 057 451 A1 is that it is comparatively complex and requires numerous components. These are correspondingly expensive, heavy and require a comparatively large Space. In addition, they are also freeze-endangered, if the start at

Temperatures should be below freezing.

The object of the present invention is now to provide an anode circuit which avoids all the disadvantages mentioned and allows a simple, safe and reliable starting of the fuel cell equipped with it. In addition, a suitable method for operating such an anode circuit in the

Cold start case can be specified.

According to the invention the object is achieved by the features in the characterizing part of claim 1. A method according to the invention is specified in claim 9. In addition, claim 10 gives a particularly preferred use of

Device according to the invention and / or the method according to the invention.

Further advantageous embodiments of the solution according to the invention will become apparent from the dependent device claims.

In the anode circuit according to the invention, it is provided that a

Valve means for shutting off a flow through the recirculation line is arranged in the recirculation line. Regardless of how the recirculation conveyor is constructed, such a valve device can recirculate by blocking the recirculation line in certain operating situations

extraordinarily simple and efficient. As a result, accumulated condensate is not transported back into the still cold fuel cell during startup, but it is only the closed volume of the anode circuit raised to the working pressure and fresh fuel, which flows into the anode circuit, mixed with the at rest in the anode circuit typically located air.

This will very quickly sufficient hydrogen partial pressure in the

Anode room reached. The fuel cell can be activated very quickly without any accumulated condensate and liquid condensing in the fuel cell obstructing or delaying the starting process.

According to a particularly favorable and advantageous development of the invention, the valve device can be designed as a shut-off valve or flap. A simple shut-off valve or a simple flap can efficiently into the anode circuit without significant additional effort in terms of space, weight and cost to get integrated. As a result, the recirculated gas stream can be shut off at least temporarily during the cold start.

In a further particularly favorable and advantageous embodiment of the

According to the invention Anodenkreislaufs it can also be provided that the valve device is designed integrated into the recirculation conveyor. Such a valve device integrated in the recirculation conveyor device is even smaller in terms of the space requirement, since, for example, in any case

existing connection area for the recirculation conveyor such a valve device can be placed very easily.

According to a further embodiment of the anode circuit according to the invention, it may be provided that the recirculation conveyor is designed as a gas jet pump, which is drivable by the fresh fuel. In an advantageous development thereof, the valve device may be in the gas jet pump

be formed, wherein a suction port for the recirculated gas stream can be closed by the valve means. Such an integration of the valve device in the gas jet pump is particularly simple and efficient, since in this way the recirculated gas stream is shut off and the recirculation effect of the gas jet pump is prevented.

In a further very advantageous embodiment of this, it can then be provided that a nozzle for the propulsion jet is positioned centrally in a suction area connected to the suction, wherein the nozzle is displaceable in its axial direction, the size of the connection between the intake and a Blending zone depending on the axial position of the nozzle has its full flow-through cross-section or no flow-through cross-section. Due to the possibility of the nozzle in axial

To shift direction, so the flow cross-section in the intake can be reduced to zero. This makes it very easy and efficient in the smallest

durchströmbaren cross-section of the entire anode circuit reaches a closing just this cross section. The mechanical complexity and the size of the components required for this purpose are minimal, since at no other place in the

Anodenkreislauf a smaller flow-through cross section is present. Closing the smallest possible cross section according to this embodiment of the The anode circuit according to the invention is thus structurally particularly simple and can be implemented very efficiently with small, lightweight and cost-effective means.

In the inventive method for starting a fuel cell system with an anode circuit according to one or more of the above

Embodiments it is now provided that during the boot process the

Valve device is closed at least temporarily. Such an at least temporary closing of the valve device during the starting process makes it possible to prevent the recirculation, which prevents accumulated condensate from being transported back into the cold fuel cell and thus the working pressure in the closed anode circuit is reached very quickly and accordingly a sufficiently high hydrogen level very early Partial pressure for the activation of the fuel cell is present.

If in the anode circuit, as is well known and customary, a water separator and a drain valve for water is present, then this may also be opened at least briefly before opening the valve means to drain in the region of the recirculation line and arranged in her Wasserabscheiders accumulated condensate and thus to prevent the entry of just this condensate in the region of the fuel cell after opening the valve device itself.

As already mentioned several times, the particular advantage of the anode circuit according to the invention is that it is ideally suited to achieve a start or cold start of the fuel cell or a equipped with her fuel cell system. Since cold start conditions play a decisive role, in particular in mobile fuel cell systems, since, for example, vehicles must frequently be shut down and restarted, the particularly preferred use of the

Anodenkreislaufs or the method for starting a fuel cell system with such an anode circuit for use in vehicles. The use in stationary systems would in principle also be possible, but due to the less frequently occurring starts and the lower requirements in terms of the shortest possible start time of the fuel cell system here more easily dispensable. Further advantageous embodiments of the anode circuit according to the invention will become apparent from the remaining dependent claims and are based on the

Embodiment clear, which will be described below with reference to the figures.

Showing:

1 shows a principle indicated vehicle with a fuel cell system,

which has an anode circuit according to the invention;

Fig. 2 shows an alternative embodiment for an anode circuit according to the invention; and

Fig. 3 shows a possible embodiment of the integration of a valve device in a

Gas jet pump.

In the illustration of Figure 1, a vehicle 1 indicated in principle with a fuel cell system 2 can be seen, which is to be designed for the provision of electrical power, in particular of electrical drive power for the vehicle 1. Core of the fuel cell system 2 is a fuel cell 3, which is designed as a stack of individual cells, as a so-called fuel cell stack. The fuel cell 3 should be realized in the embodiment shown here as a PEM fuel cell. This construction of fuel cells with

Proton exchange membranes are well known and common for vehicle applications. The fuel cell 3 comprises an anode compartment 4 and a cathode compartment 5. The cathode compartment 5 is supplied with air as an oxygen-containing medium via an air conveying device 6. This air can through an optional humidifier 7 in the

Cathode space 5 flow. The oxygen-depleted and laden with product water exhaust air then passes in the embodiment shown here again on the optional humidifier 7, in the area they give their moisture to the dry supply air to the cathode compartment 5, from the vehicle 1. Other components in the exhaust air For example, a turbine or the like are conceivable and known from the general state of the art. Since this is not relevant for the present invention, a corresponding representation has been omitted.

Hydrogen is supplied from a compressed gas reservoir 8 via a metering and regulating valve 9 to the anode chamber 4 of the fuel cell 3. The hydrogen flows into the Anode space 4 and is at least partially implemented there. Unconsumed hydrogen passes through a recirculation line 10 and a

Recirculation conveyor 11, which is indicated here as a hydrogen circulation fan 110, back to the entrance of the anode compartment 4 and this is mixed with fresh hydrogen from the compressed gas storage 8 again supplied. This structure is also referred to as anode circuit 12. In the region of the recirculation line 10 is typically also next to the recirculation conveyor 11 a

Water separator 13 is arranged with a drain valve 14. During operation of the fuel cell system 2, water and inert gas, which has diffused through the membranes of the fuel cell 3 from the cathode compartment 5 into the anode compartment 4, accumulate over time in the region of the anode circuit 12. The water can now be drained from time to time. Since the volume of the anode circuit 12 is constant, decreases with increasing proportion of inert gases in the anode circuit 12 the

Hydrogen concentration. In addition to the water can therefore via the drain valve 14 from time to time or, for example, as a function of substance concentrations, the

Accumulated amount of water or the like, gas can be drained with to keep the concentration of hydrogen in the anode circuit 12 in the desired range. All this is as far as has been described so far, known from the general state of the art.

Of the conventional fuel cell systems 2, the fuel cell system 1 shown here now differs in that in the field of

Rezirkulationsleitung 10 also a valve device 15 is arranged. About this valve means 15, the recirculated gas stream can shut off. As a result, the recirculation can be deactivated at least temporarily, in particular during the starting process. This prevents that accumulating condensate is transported into the cold fuel cell 3. The valve device 15 can be designed, for example, as a solenoid valve, as indicated in FIG. 1, or as a simple, actively actuable flap or the like. This is extremely easy and efficient. The valve device 15 can thus be realized simply, inexpensively, easily and with minimal space required.

In the illustration of Figure 2, an alternative embodiment of the anode circuit 12 can be seen. In the embodiment shown here is the

Rezirkulationsfördereinrichtung 11 formed as a gas jet pump 111. Otherwise corresponds to the structure shown in Figure 2 in its functionality largely the structure shown in Figure 1. Since when using a gas jet pump 111 as

Rezirkulationsfördereinrichtung 11 is a dosage typically via valves in the gas jet pump 111, instead of the pressure control and metering valve 9 in the schematic diagram of Figure 1 here a shut-off valve 16 and a pressure control valve 17 is shown, wherein the representation of the actual metering valves in the

Gas jet pump 111 has been omitted. The functionality with the valve device 15 in the recirculation line 10 of the anode circuit 12 is substantially the same, as already described in the illustration of Figure 1.

In order to further save space and further reduce the cost of the valve device 15, this can be formed in the recirculation conveyor 11 with integrated. This will be explained in a possible embodiment in Figure 3 using the example of the gas jet pump 111 as recirculation conveyor 11. The

Sectional view of Figure 3 shows the gas jet pump 111 and the

Recirculation line 10, which in the region of an intake opening 18 with the

Gas jet pump 11 is connected. The suction opening 18 is followed by a

annular intake 19 in the gas jet pump 111 on, in

Flow direction of the gases before the actual mixing zone 20, the region of the anode circuit 12 with the smallest flow-through cross-section. The fresh gas flow from the pressure regulator 17 flows through a nozzle 21 for the propulsion jet into the area of the gas jet pump 111. This Treibstrahldüse 21 runs conically in its front region, as well as the Treibstrahldüse 21 surrounding part of the

Aspiration 19. The emerging from the propulsion jet nozzle 21 hydrogen flow as a propellant gas stream flows into the mixing zone 20 and sucks on vacuum and

Pulse exchange the recirculated gas stream from the region of the suction port 18 and the intake 19, so that through the mixing zone 20, a mixture of the two gas streams in regular operation to the anode compartment 4 of the fuel cell 3 flows. By moving the Treibstrahldüse 21, it is now possible, this in its axial

Direction, as indicated by the double arrow 22, to move so that the right in the illustration of Figure 3 end of the Treibstrahldüse 21, which is also provided with an elastomeric seal 23, sealingly abuts the walls of the intake 19. As a result, the connection between the mixing zone 20 and the

Suction port 18 is closed and prevents recirculation of gas in the anode circuit 12. The displaceable in the axial direction 22 Treibstrahldüse 21 thus forms in this area, the valve device 15. This is a particularly compact construction, since the lowest flow-through cross-section of the anode circuit 12 is present in the intake region 19 or in the mixing zone 20. To close this is therefore possible with correspondingly simple and small-sized elements, so that with minimal energy consumption, the very small and efficient valve device 15 can be operated.

Claims

claims

An anode circuit (12) for a fuel cell (3) having a recirculation line (10) which connects an output of an anode compartment (4) of the fuel cell (3) to an input of the anode compartment (4) of the fuel cell (3), and a recirculation conveyor (11),

characterized in that

in the recirculation line (10) a valve means (15) for shutting off a flow through the recirculation line (10) is arranged.

2. Anodenkreislauf (12) according to claim 1,

characterized in that

the valve device (15) is designed as a shut-off valve or flap.

3. anode circuit (12) according to claim 1 or 2,

characterized in that

the valve device (15) is designed to be integrated in the recirculation conveyor (11).

4. Anodenkreislauf (12) according to claim 1, 2 or 3,

characterized in that

the recirculation conveyor (11) is designed as a gas jet pump (111), which is driven by fresh fuel as a propellant gas stream.

5. Anodenkreislauf (12) according to claim 4,

characterized in that

the valve device (15) is formed in the gas jet pump (111), wherein the valve device (15) a suction port (18) or a suction region (19) for the recirculated gas stream is closable.

6. Anodenkreislauf (12) according to claim 5,

characterized in that

a nozzle (21) for the propulsion jet is positioned centrally in a suction area (19) connected to the suction opening (18), the nozzle (21) being displaceable in its axial direction (22), the size of the connection between the suction opening ( 18) and a mixing zone (20) depending on the axial position of the nozzle (21) has its full flow-through cross-section, no flow-through cross-section or any intermediate positions.

7. Anodenkreislauf (12) according to claim 6,

characterized in that

the nozzle (21) on its circumference facing the walls of the suction area (19) with a contour of the walls of the suction area (19)

corresponding form is formed.

8. Anodenkreislauf (12) according to claim 6 or 7,

characterized in that

the nozzle (21) on its the walls of the suction area (19) facing surfaces and / or the walls of the suction (19) on its nozzle (21) facing surfaces a seal, preferably made of an elastomer having.

9. A method for starting a fuel cell system (2) with a

An anode circuit (12) according to any one of claims 1 to 8,

characterized in that

during the starting process of the fuel cell system (2), the valve device (15) is closed at least temporarily.

10. The use of the anode circuit (12) according to any one of claims 1 to 8 and / or the method according to claim 9 in a fuel cell system (2), which is provided for the provision of electrical power in a vehicle (1).