Water separator, anode subsystem having water separator

Abstract

The invention relates to a water separator (1) for separating water from a water-containing gas stream, in particular a water-containing anode gas stream in an anode circuit of an anode subsystem (14) for supplying a fuel cell stack (15) with hydrogen, the water separator comprising a housing (2) having a cavity (3), into which an inlet channel (4) and an outlet channel (5) lead, wherein the outlet channel (5) has wall surfaces (6) and, at the end of the outlet channel remote from the cavity (3), an outlet opening (7) which is inwardly offset, all around, relative the wall surfaces (6) and which is surrounded by a hollow cylindrical collar (8), such that the wall surfaces (6) and the collar (8) form an annular collection basin (9) for water droplets. The invention also relates to an anode subsystem (14) having a water separator (1) according to the invention.

Description

[0001] Description

[0002] title

[0003] Water separator, anode subsystem with water separator

[0004] The invention relates to a water separator for separating water from a gas-containing gas stream, in particular a water-containing anode gas stream in an anode circuit of an anode subsystem for supplying a fuel cell stack with hydrogen. The invention further relates to an anode subsystem for supplying a fuel cell stack with hydrogen, comprising a water separator according to the invention.

[0005] The preferred field of application of the invention is fuel cell systems, in particular mobile fuel cell systems or fuel cell vehicles.

[0006] State of the art

[0007] Polymer electrolyte membrane (PEM) fuel cells convert hydrogen into electrical energy, heat, and water with the help of oxygen. The hydrogen is fed to an anode of the PEM fuel cell, and the oxygen to a cathode, which is separated from the anode by a polymer electrolyte membrane. Ambient air typically serves as the oxygen source. In practice, to increase electrical output, several fuel cells are stacked together to form a fuel cell stack. Supply ducts run through the fuel cell stack, supplying the individual fuel cells with hydrogen and air. The anode gas and moist exhaust air escaping from the fuel cells are removed via exhaust ducts.

[0008] A systemic approach has been established in which the anode gas escaping from the fuel cells is actively recirculated using a gas delivery unit and / or passively recirculated, as this still contains residual hydrogen. The recirculated anode gas also contains product water, which diffuses from the cathode side to the anode side. Before the recirculated anode gas enters the fuel cell stack, the product water must be separated from the gas stream and drained away. Separation is typically achieved using a water separator, which, in addition to its separation function, also performs a storage function. This means that the separated water is collected in a storage volume of the water separator. Only when the storage volume is full is a drain valve opened, through which the storage volume can be emptied.

[0009] In fuel cell systems, so-called "sedimenters" are often used as water separators, which separate the water using the principle of sedimentation. The gas stream containing the product water is fed into a cavity of the water separator, which slows the gas flow. This slows the flow. This slows the flow and separates the liquid phase from the gas phase, causing the liquid phase to fall or rain down under the force of gravity. In this way, separation efficiencies of 85% and more can be achieved. In practice, however, it has been shown that water droplets settle in the ceiling area of ​​the water separator and do not rain down, but are carried along by the gas flow towards the outlet of the water separator. This means that this water is not separated, thereby reducing the separation efficiency of the water separator.

[0010] The present invention is concerned with the task of optimizing the separation efficiency of a water separator, in particular when used in an anode subsystem of a fuel cell system.

[0011] To achieve this object, the water separator having the features of claim 1 and the anode subsystem having the features of claim 8 are proposed. Advantageous further developments of the invention can be found in the respective subclaims.

[0012] Disclosure of the invention

[0013] A water separator is proposed for separating water from a water-containing gas stream, in particular a water-containing anode gas stream in an anode circuit of an anode subsystem for supplying a fuel cell stack with hydrogen. The water separator comprises a housing with a cavity into which an inlet channel and an outlet channel open. The outlet channel has wall surfaces and, at its end facing away from the cavity, an outlet opening circumferentially indented from the wall surfaces and enclosed by a hollow cylindrical collar, so that the wall surfaces and the collar form an annular collecting basin for water droplets.

[0014] The annular collar surrounding the outlet opening prevents water droplets precipitating in the ceiling area or on the wall surfaces of the outlet duct, which are driven toward the outlet opening by the gas flow, from entering the outlet opening. Instead, the water droplets collect in the annular collecting basin or fall downwards from there by gravity. This significantly improves the separation efficiency of the water separator.

[0015] According to a first preferred embodiment of the invention, the hollow cylindrical collar is formed by the housing of the water separator. For example, the collar can be molded in. Therefore, no additional components are required that would have to be installed separately.

[0016] According to a further preferred embodiment of the invention, the hollow cylindrical collar is formed by a sleeve. Using the sleeve, an existing water separator can also be retrofitted or upgraded to a water separator according to the invention. The sleeve is preferably inserted into the outlet opening, for example, screwed or pressed in. The height of the collar can then be determined by the screw-in or press-in depth.

[0017] Furthermore, the cavity preferably has a bottom region that is spaced apart from a bottom region of the inlet channel and a bottom region of the outlet channel. This means that there is a height difference between the bottom region of the cavity and the bottom regions of the inlet and outlet channels. This is intended to prevent water collecting in the cavity from entering the inlet or outlet channel. This is only possible when the cavity is filled with water to such an extent that the fill level corresponds to the height of the bottom regions of the inlet and outlet channels. To prevent this, the cavity can be emptied in good time. In a further development of the invention, it is proposed that the bottom region of the inlet channel runs at an angle so that water droplets collecting in the collecting basin are guided over the bottom region towards the cavity.The water then flows back into the cavity via the floor area and can be discharged with the water collecting there.

[0018] Alternatively or additionally, it is proposed that the annular collecting basin be connected to the cavity via a channel formed in the housing. Water collecting in the collecting basin can thus be returned to the cavity via the channel. For this purpose, the channel preferably has a gradient toward the cavity, so that the water is returned by gravity.

[0019] Advantageously, the inlet channel and / or the outlet channel are oriented substantially tangentially with respect to the cavity. This tangential orientation has the advantage of creating a swirl in the gas stream, particularly when introducing a water-containing gas stream into the cavity of the water separator. This swirl promotes the precipitation of the accumulating water droplets on the ceiling.

[0020] Since the preferred application of the proposed water separator is an anode subsystem for supplying a fuel cell stack with hydrogen, an anode subsystem comprising a water separator according to the invention is also proposed. Since the water separator has an increased separation efficiency, the ingress of water into the fuel cell stack is minimized via the anode subsystem. If the anode subsystem has a gas delivery unit downstream of the water separator, this is also protected from water ingress.

[0021] According to a preferred embodiment of the invention, the anode subsystem comprises an adapter plate for connection to the fuel cell stack. This makes it easier to connect the anode subsystem to a fuel cell stack. The adapter plate can, for example, have connections for supply and disposal lines of the fuel cell stack, via which anode gas can be easily supplied and removed or recirculated. To simplify the anode subsystem, it is proposed that the adapter plate forms a ceiling region of the cavity, the inlet channel, and / or the outlet channel. The housing of the water separator can therefore be open in some regions, preferably at the top, thus saving material and installation space.

[0022] The invention and its advantages are described in more detail below with reference to the accompanying drawings. These show:

[0023] Fig. 1 shows a schematic longitudinal section through a fuel cell stack with an anode subsystem,

[0024] Fig. 2 shows a horizontal section through a water separator according to the invention,

[0025] Fig. 3 a) a vertical section and b) a horizontal section through the outlet channel of the water separator of Figure 2,

[0026] Fig. 4 a) a vertical section and b) a horizontal section through the outlet channel of a second water separator according to the invention and

[0027] Fig. 5 a) a horizontal section and b) a vertical section through a third water separator according to the invention.

[0028] Detailed description of the drawings

[0029] Figure 1 shows a fuel cell stack 15 comprising several fuel cells 20 arranged one above the other. To supply each fuel cell 20 with hydrogen, the fuel cell stack 15 is traversed by a supply channel 17. A discharge channel 18 extending through the fuel cell stack 15 serves to remove anode gas. The flow direction 21 of the hydrogen or anode gas through the fuel cells 20 is indicated by arrows.

[0030] Since the anode gas exiting the fuel cells still contains hydrogen, it is recirculated via an anode subsystem 14, i.e., fed back to the fuel cells 20. In the illustrated anode subsystem 14, which is connected to the fuel cell stack 15 via an adapter plate 16, recirculation is actively effected by means of a gas delivery unit 19. Since recirculated anode gas contains water that has passed from the cathode side to the anode side through diffusion processes, the anode subsystem 14 also includes a water separator 1 for separating water from the anode gas stream. This is intended to prevent water from being introduced into the gas delivery unit 19 and / or the fuel cell stack 15. To increase the separation efficiency of the water separator 1, the latter is designed according to the invention, for example, analogously to Figures 2 to 4.

[0031] The water separator 1 according to the invention, shown in Figure 2, has a housing 2 in which a cavity 3 as well as an inlet channel 4 and an outlet channel 5 are formed. A water-containing gas stream enters the cavity 3 via the inlet channel 4. Since the inlet channel 4 is oriented essentially tangentially with respect to the cavity 3, the gas stream is swirled in the cavity 3, thereby improving the separation into the liquid phase and the gas phase. The liquid phase, or the liquid water, falls downwards under gravity and collects in a bottom region 11 of the cavity 3. Since the bottom region 11 of the cavity 3 is lower than the inlet and outlet channels 4, 5 or their bottom regions 12, 13, the water remains in the cavity 3, and the gas phase leaves the water separator 1 via the outlet channel 5.

[0032] Water droplets can settle in a ceiling area of ​​the cavity 3; they do not rain down but are entrained by the gas flow into the outlet channel 5. The water droplets are driven towards an outlet opening 7 of the outlet channel 5 via wall surfaces 6 that define the outlet channel 5. To prevent the water droplets from being discharged from the water separator 1 via the outlet opening 7 together with the gas flow, the outlet opening 7 is defined by a hollow cylindrical collar 8. The water droplets cannot overcome this collar because the gas flow pushes them back. Instead, the water droplets collect in an annular collecting basin 9 formed by the wall surfaces 6 and the collar 8. From there, the water droplets move towards the bottom area 13 of the outlet channel 5, driven by gravity.Since the bottom area 13 forms a slope, the water can flow back from the outlet opening 7 into the cavity 3 via the slope during phases in which the water separator is not in operation.

[0033] As can be seen in particular from Figures 3a) and 3b), the hollow cylindrical collar 8 is formed by a sleeve 10 that is inserted, for example, pressed, into the outlet opening 7. The sleeve 10 can also be subsequently inserted to upgrade a water separator 1.

[0034] Alternatively, the collar 8 can also be formed integrally with the housing 2, as shown by way of example in Figures 4a) and 4b). Another possibility for draining water accumulating in the collecting basin 9 is shown by way of example in Figures 5a) and 5b). Here, the collecting basin 9 is connected to the cavity 3 via a channel 22 (see Figure 5a)). Since the channel 22 has a gradient towards the cavity 3 (see Figure 5b), gravity can also be used to drain the water.

Claims

Claims 1. A water separator (1) for separating water from a water-containing gas stream, in particular a water-containing anode gas stream in an anode circuit of an anode subsystem (14) for supplying a fuel cell stack (15) with hydrogen, comprising a housing (2) with a cavity (3) into which an inlet channel (4) and an outlet channel (5) open, wherein the outlet channel (5) has wall surfaces (6) and, at its end facing away from the cavity (3), an outlet opening (7) which is circumferentially indented from the wall surfaces (6) and is enclosed by a hollow cylindrical collar (8), such that the wall surfaces (6) and the collar (8) form an annular collecting basin (9) for water droplets.

2. Water separator (1) according to claim 1, characterized in that the hollow cylindrical collar (8) is formed by the housing (2).

3. Water separator (1) according to claim 1, characterized in that the hollow cylindrical collar (8) is formed by a sleeve (10) which is preferably inserted, for example screwed or pressed, into the outlet opening (7).

4. Water separator (1) according to one of the preceding claims, characterized in that the cavity (3) has a bottom region (11) which is spaced from a bottom region (12) of the inlet channel (4) and a bottom region (13) of the outlet channel (5).

5. Water separator (1) according to claim 4, characterized in that the bottom region (12) of the inlet channel (4) runs obliquely, so that water drops collecting in the collecting basin (9) are guided over the bottom region (12) in the direction of the cavity (3).

6. Water separator (1) according to one of the preceding claims, characterized in that the annular collecting basin (9) is connected to the cavity (3) via a channel (22) formed in the housing (2), wherein the channel (22) preferably has a gradient in the direction of the cavity (3).

7. Water separator (1) according to one of the preceding claims, characterized in that the inlet channel (4) and / or the outlet channel (5) is / are aligned substantially tangentially with respect to the cavity (3).

8. Anode subsystem (14) for supplying a fuel cell stack (15) with hydrogen, comprising a water separator (1) according to one of the preceding claims.

9. Anode subsystem (14) according to claim 8, characterized in that the anode subsystem (14) comprises an adapter plate (16) for connection to the fuel cell stack (15), wherein preferably the adapter plate (16) forms a ceiling region of the cavity (3), the inlet channel (4) and / or the outlet channel (5).

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