Water separator, anode subsystem with 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 (12) for supplying a fuel cell stack (13) with hydrogen, comprising a housing (2) with a cavity (3) into which an inlet channel (4) and an outlet channel (5) open, wherein the cavity (3), the inlet channel (4) and the outlet channel (5) are bounded by a cover (6) which, at the transition from the cavity (3) to the outlet channel (5), rests on a support beam (7) which extends over the entire width of the outlet channel (5). The invention further relates to an anode subsystem (12) with a water separator (1) according to the invention.

Description

[0001] 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.

[0002] The preferred field of application of the invention is fuel cell systems, in particular mobile fuel cell systems or fuel cell vehicles. State of the art

[0003] 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 channels run through the fuel cell stack, supplying the individual fuel cells with hydrogen and air. The anode gas escaping from the fuel cells, as well as the moist air or exhaust air escaping from the fuel cells, are removed via exhaust channels.

[0004] 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 is transferred from the cathode side to the anode side through diffusion processes. 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.

[0005] In fuel cell systems, so-called "sedimenters" are often used as water separators, which separate the water according to 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.

[0006] 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.

[0007] To achieve this object, the water separator having the features of claim 1 and the anode subsystem having the features of claim 7 are proposed. Advantageous further developments of the invention can be found in the respective subclaims. Disclosure of the invention

[0008] 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 cavity, the inlet channel, and the outlet channel are delimited by a ceiling, which rests on a support beam at the transition from the cavity to the outlet channel. The support beam extends across the entire width of the outlet channel.

[0009] The joist prevents water droplets that have settled on the ceiling near the cavity from being carried by the gas flow over the ceiling into the outlet duct. This is because the joist extending downwards from the ceiling forms a barrier that the water droplets cannot overcome. When the water droplets reach the joist, they run down the joist under gravity and then drip off the lower edge of the joist, on the side of the joist facing the cavity. The water droplets then fall into the cavity and can be discharged from the water separator along with the water collected there. The joist thus increases the separation efficiency of the water separator.

[0010] The joist is preferably formed integrally with the housing and / or the ceiling. If the joist and ceiling are separate components, any gaps between the ceiling and the joist are sealed to prevent water from penetrating the gap.

[0011] In a further development of the invention, it is proposed that the underside of the beam be formed with a slope or an arch. This means that the lower edge or underside of the beam is sloped or arched. The slope or arched design of the underside of the beam has the advantage that water droplets running down the beam are guided further downwards via the slope or arch. This reduces the height from which the water droplets fall, and they can be drained away in a more controlled manner. The slope can run along the entire length of the beam in one direction or the other. However, two slopes can also be placed opposite one another in a gable-like manner. The arch can be circular, oval, or parabolic.

[0012] Preferably, the bottom beam forms a drip edge on its side facing the cavity, extending over the entire length of the bottom beam. The drip edge is shaped to facilitate the dripping of water droplets running down the bottom beam. This is the case, for example, if the drip edge reduces the contact area of ​​the water droplets with the bottom beam, forcing the water droplets to assume a more spherical shape. If the bottom beam forms a slope or curve on its underside, the drip edge follows the slope or curve.

[0013] Alternatively or additionally, it is proposed that the beam form a groove on the side facing the cavity, extending the entire length of the beam. The groove can be used to guide the water droplets running down the beam toward the cavity in a controlled manner. This is especially true if the beam has a slope or curve on its underside, as in this case, the groove follows the slope or curve.

[0014] The channel formed by the beam can be open to the side or upward. If the channel is open to the side, it is pressed against the beam by the gas flow toward the outlet channel. A channel open to the top, on the other hand, does not require a gas flow to keep the water in the channel.

[0015] 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.

[0016] 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.

[0017] 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 the ceiling that defines the cavity, the inlet channel, and the outlet channel. The housing of the water separator can therefore be open in some areas, preferably at the top, thus saving material and installation space. If the support beam is formed integrally with the ceiling, it can be a component of the adapter plate.However, the beam and the ceiling can also be separate components, so that the beam is part of the housing of the water separator.

[0018] The invention and its advantages are described in more detail below with reference to the accompanying drawings. These show: Fig. 1 a schematic longitudinal section through a fuel cell stack with an anode subsystem, Fig. 2 a horizontal section through a water separator according to the invention, Fig. 3 a) to e) each show a side view of a beam and Fig. 4 a) to c) each show a vertical section through a beam. Detailed description of the drawings

[0019] Fig. Figure 1 shows a fuel cell stack 13 comprising several fuel cells 18 arranged one above the other. A supply channel 15 runs through the fuel cell stack 13 to supply each fuel cell 18 with hydrogen. A discharge channel 16 runs through the fuel cell stack 13 to remove anode gas. The flow direction 19 of the hydrogen or anode gas through the fuel cells 18 is indicated by arrows.

[0020] Since the anode gas emerging from the fuel cells 18 still contains hydrogen, it is recirculated via an anode subsystem 12, i.e., fed back to the fuel cells 18. In the illustrated anode subsystem 12, which is connected to the fuel cell stack 13 via an adapter plate 14, the recirculation is actively effected by means of a gas delivery unit 17. Since the recirculated anode gas contains water that has passed from the cathode side to the anode side through diffusion processes, the anode subsystem 12 also comprises 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 17 and / or into the fuel cell stack 13. To increase the separation efficiency of the water separator 1, the latter is designed according to the invention, for example analogously to the Fig. 2 to 4, trained.

[0021] The one in the Fig. 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 of the cavity 3. Since the bottom region of the cavity 3 is lower than the inlet and outlet channels 4, 5 or their bottom regions, the water remains in the cavity 3, and the gas phase leaves the water separator 1 via the outlet channel 5.

[0022] On a ceiling 6 bordering the cavity 3 (see Fig. 1) Water droplets can precipitate and not rain down. To prevent the precipitating water droplets from being driven by the gas flow over the ceiling 6 into the outlet channel 5, the ceiling 6 rests on a support beam 7. The support beam 7 forms a barrier for the water droplets.

[0023] The underside of the beam 7 can be terminated with a straight or horizontal edge, so that it has the same height across the entire width of the outlet channel. However, the underside of the beam 7 can also form a slope 8 or a curve 9. Preferred embodiments are shown in the Fig. 3a) to 3e). A water droplet running down the beam 7 can be guided downwards via the slope 8 or the arch 9, so that the fall height decreases when it finally drips off the beam 7. The slope 8 can also comprise two slopes 8 arranged in a gable-like manner, as shown for example in the Fig. 3d). The arc 9 does not necessarily have to be circular, but can also be parabolic, for example (see Fig. 3e)).

[0024] It is also advantageous if - as exemplified in the Fig. 4a) to 4c) - the beam 7 forms a drip edge 10 and / or channel 11 extending over its entire length. The drip edge 10 facilitates the dripping of a water droplet running down the beam 7, as it reduces the contact area of ​​the water droplet with the beam 7. A water droplet running down the beam 7 can be collected and drained away in a controlled manner via the channel 11. This applies in particular if the underside of the beam 7 forms a slope 8 or a curve 9 and the channel 11 follows the slope 8 or the curve 9.

Claims

[1] 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 (12) for supplying a fuel cell stack (13) with hydrogen, comprising a housing (2) with a cavity (3) into which an inlet channel (4) and an outlet channel (5) open, wherein the cavity (3), the inlet channel (4) and the outlet channel (5) are delimited by a cover (6) which, in the transition from the cavity (3) to the outlet channel (5), rests on a support beam (7) which extends over the entire width of the outlet channel (5). [2] Water separator (1) according to claim 1, characterized by that the beam (7) forms a slope (8) or an arch (9) on the underside. [3] Water separator (1) according to claim 1 or 2, characterized bythat the support beam (7) forms a drip edge (10) on its side facing the cavity (3), which extends over the entire length of the support beam (7), preferably following the slope (8) or the curve (9). [4] Water separator (1) according to one of the preceding claims, characterized by that the support beam (7) forms a groove (11) on its side facing the cavity (3) which extends over the entire length of the support beam (7), preferably following the slope (8) or the curve (9). [5] Water separator (1) according to claim 4, characterized by that the channel (11) is open to the side or upwards. [6] Water separator (1) according to one of the preceding claims, characterized by that the inlet channel (4) and / or the outlet channel (5) is / are aligned substantially tangentially with respect to the cavity (3). [7] Anode subsystem (12) for supplying a fuel cell stack (13) with hydrogen, comprising a water separator (1) according to one of the preceding claims. [8] Anode subsystem (12) according to claim 7, characterized by that the anode subsystem (12) comprises an adapter plate (14) for connection to the fuel cell stack (13), wherein preferably the adapter plate (14) forms the cover (6).

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