Water separator for a fuel cell system

Abstract

The invention relates to a water separator (10) for a fuel cell system, having a separating device (20) for separating liquid water (W) from a gas flow (G), a water collecting region (36), in which the liquid water (W) separated from the gas flow (G) by the separating device (20) collects, and a discharge line (28) for discharging the water (W) located in the water collecting region (36), the discharge line (28) having an inlet opening (34) which is located in the water collecting region (36).

Description

[0001] Water separator for a fuel cell system

[0002] The invention relates to a water separator for a fuel cell system, comprising a separation device for separating liquid water from a gas flow, a water collection region in which the liquid water separated from the gas flow by the separation device collects, and a discharge line for discharging the water located in the water collection region, wherein the discharge line has an inlet opening located in the water collection region.

[0003] The invention further relates to a fuel cell system having at least one fuel cell, a gas circulation path connected to the fuel cell for an anode gas flow to be at least partially returned to the fuel cell, and a water separator arranged along the gas circulation path.

[0004] Furthermore, the invention relates to a method for removing liquid water from a gas flow by means of a water separator, comprising the steps of: separating liquid water from the gas flow by means of a separation device of the water separator, collecting the water separated from the gas flow by the separation device in a water collection region of the water separator and discharging the water located in the water collection region by means of a discharge line which has an inlet opening located in the water collection region.

[0005] Generic water separators are used, for example, in fuel cell systems where the gas flow passed through the water separator is an anode gas flow comprising gaseous hydrogen and liquid water, which is then returned to the fuel cell after the liquid water has been separated and enriched with gaseous hydrogen. In such fuel cell systems, it is also necessary to prevent the nitrogen concentration in the gas flow from exceeding a concentration limit. To prevent such a limit from being exceeded, the water separator can be used not only for water separation but also to divert the gas flow from a gas circulation path.

[0006] From the document DE 10 2021 105 669 A1, for example, a gas management device is known which comprises an outlet valve for discharging liquid and gas.

[0007] This and other devices have the problem that, after operation of a fuel cell system, water remaining in the water separator's water collection chamber can freeze at low ambient temperatures, and the water separator's discharge line used to drain the water can become frozen. During subsequent commissioning of the fuel cell system, the water cannot be drained from the water collection chamber due to the freezing of the discharge line, which can significantly impair the operation of the fuel cell system and cause damage to the fuel cell system.

[0008] The provision of an additional heater to thaw the frozen water would lead to a significant increase in the production costs and energy requirements of the fuel cell system and should therefore be avoided.

[0009] The object underlying the invention is therefore to enable rapid defrosting of an iced-up discharge line, particularly in the region of the discharge line's inlet opening, of a water separator of a fuel cell system. This object is achieved by a water separator of the type mentioned above, wherein the water separator according to the invention has one or more water guide surfaces configured to specifically direct the liquid water separated from the gas flow into a dew zone located at the discharge line's inlet opening in the water collection area, in order to break up any icing on the discharge line by means of the water specifically directed into the dew zone.

[0010] The gas flow can, for example, be an anode gas flow of the fuel cell system. When the fuel cell system is started up, the gas flow and the water contained in the anode gas flow heat up by approximately 0.7°C / s to a temperature of approximately 60°C. If, when the fuel cell system is started up, the separated water cannot initially be discharged due to icing of the discharge line in the water collection area, the separated warm water ensures a direct heat input into the thawing zone, so that a melt channel leading to the inlet opening of the discharge line quickly forms in the frozen water. Even if the remaining water in the water collection area is still frozen, newly separated water can be discharged directly via the melt channel and the discharge line. The remaining water in the water collection area then also gradually thaws during a warm-up phase.

[0011] The water separator according to the invention can comprise a separator housing. The separator housing can be flowed through by the gas flow. The separator housing preferably has a flow inlet through which the gas flow can flow into the separator housing. Furthermore, the separator housing preferably has a flow outlet through which the gas flow can flow out of the separator housing after the water has been separated. The separation device is preferably located in the separator housing. The separation device can be, for example, a collecting separator, such as a knitted fabric separator or a nonwoven separator, a deflection separator, such as an impact separator or a lamella separator, or a centrifugal separator, such as a cyclone or a centrifuge. The water collection area is preferably located in the separator housing, but can alternatively also be designed separately, e.g., as a tank.In an advantageous embodiment, the water collection area is located below the separation device in the direction of gravity during normal operation, so that separated water is directed into the water collection area by gravity. The anode gas flow can be a recirculation flow of the fuel cell system.

[0012] In a preferred embodiment of the water separator according to the invention, at least one water guide surface is a component of the separation device. The separation device can, for example, comprise one or more separation surfaces and one or more water guide surfaces. Liquid water is separated from the gas flow at the one or more separation surfaces. The liquid water separated from the gas flow is directed in a targeted manner toward the dew zone via the one or more water guide surfaces. The one or more water guide surfaces and / or the one or more separation surfaces can be components of a plate structure of the separation device.

[0013] In a further preferred embodiment, the water separator according to the invention has a separation chamber into which the gas flow can be introduced. The water guide surface of the separation device is preferably an inflow surface, which is arranged in the separation chamber and / or is configured to be flowed against by the gas flow flowing into the separation chamber. The inflow surface is preferably arranged and oriented such that it is frontally flowed against by the gas flow flowing into the separation chamber. The direct, in particular frontal, flow against the inflow surface achieves a particularly high degree of separation. The separation chamber is preferably located in the separator housing of the water separator.

[0014] In another preferred embodiment of the water separator according to the invention, the separation device has a flow guide contour designed to direct the gas flow flowing into the separation chamber, preferably frontally, onto the inflow surface. The flow guide contour preferably defines a circulating flow region in which the gas flow is guided in the circumferential direction. The flow guide contour preferably comprises a cross-sectional taper along which the gas flow coming from the circulating flow region is converged. The flow guide contour preferably comprises an alignment channel along which an intended flow direction is imposed on the gas flow coming from the cross-sectional taper.

[0015] Furthermore, a water separator according to the invention is preferred in which the water guide surface of the separating device has a contour that defines one or more drip points for the water toward the dew zone. The one or more drip points can be defined by the surface shape of the water guide surface and / or by water guiding elements on the water guide surface, such as water guide webs and / or water guide grooves and / or channels.

[0016] Furthermore, a water separator according to the invention is advantageous in which at least one water guide surface is part of the discharge line. In this case, the separated water is guided directly along the discharge line to the freezing point, ensuring that the discharge line thaws more quickly. A direct heat channel is created along the discharge line, which thaws the area surrounding the discharge line and thus also the part of the water collection area adjacent to the discharge line. Preferably, at least one drip point on the water guide surface of the separator is arranged so that the dripping water drops onto the water guide surface of the discharge line.

[0017] In another preferred embodiment of the water separator according to the invention, the water-guiding surface of the discharge line is formed by the outer wall of the discharge line. The discharge line is preferably a pipeline and / or has a circumferential line wall. The water-guiding surface is located on the outside of the discharge line, so that heat is introduced into the discharge line from the outside to the inside. Because the water-guiding surface of the discharge line is formed by the outer wall of the discharge line, even ice buildup along a longer line section can be quickly and reliably removed.

[0018] In a preferred embodiment of the water separator according to the invention, at least one water guide surface runs at a distance from and / or parallel to the discharge line. An air gap is preferably located between the water guide surface and the discharge line. This prevents component collisions caused by temperature fluctuations.

[0019] Furthermore, a water separator according to the invention is preferred in which the discharge line is designed as a riser pipe. The discharge line designed as a riser pipe preferably runs at an angle relative to a central axis of the separation chamber. A lower region of the riser pipe preferably extends into the water collection area.

[0020] The water separator according to the invention is further advantageously developed in that the discharge line is connected to a discharge valve, via which, when actuated, the water can be discharged from the water collection area via the discharge line. Upon actuation of the discharge valve, water from the water collection area is preferably sucked into and through the discharge line or forced into and through the discharge line due to the prevailing pressure conditions. The actuation of the discharge valve can be initiated, for example, by an electronic control device. For example, the electronic control device initiates actuation of the discharge valve when the water level in the water collection area has reached a water level limit.Alternatively or additionally, the electronic control device can be configured to actuate the discharge valve during startup of the fuel cell system according to a predetermined actuation routine. The actuation routine can be dependent on a current or previous ambient temperature.

[0021] The object underlying the invention is further achieved by a fuel cell system of the type mentioned above, wherein the water separator of the fuel cell system according to the invention is designed according to one of the embodiments described above. With regard to the advantages and modifications of the fuel cell system according to the invention, reference is therefore made to the advantages and modifications of the water separator according to the invention.

[0022] The object underlying the invention is further achieved by a method of the type mentioned at the outset, wherein, within the scope of the method according to the invention, the liquid water separated from the gas flow is deliberately brought into a dew zone located at the inlet opening of the discharge line in the water collection region by means of one or more water guide surfaces in order to dissolve icing of the discharge line by means of the water deliberately brought into the dew zone. By means of the method according to the invention, liquid water is preferably removed from an anode gas flow of a fuel cell system. Within the scope of the method according to the invention, a water separator according to one of the embodiments described above is preferably used. With regard to the advantages and modifications of the method according to the invention, reference is therefore also made to the advantages and modifications of the water separator according to the invention.

[0023] Preferred embodiments of the invention are explained and described in more detail below with reference to the accompanying drawings.

[0024] Fig. 1 shows a water separator according to the invention in a schematic side sectional view;

[0025] Fig. 2 shows the water separator shown in Fig. 1 in a further schematic side sectional view;

[0026] Fig. 3 shows another water separator according to the invention in a schematic sectional view from above; and

[0027] Fig. 4 shows the water separator depicted in Fig. 3 in a schematic side sectional view. Figs. 1 and 2 show a water separator 10 for a fuel cell system. The water separator 10 has a separator housing 12. A gas flow G can be introduced into the separator housing 12 via a flow inlet 14. After the water has been separated, the gas flow G can be discharged from the separator housing 12 via a flow outlet 16.

[0028] Within the separator housing 12 is a separation chamber 18 into which the gas flow G can be introduced. Within the separation chamber 18 is a separation device 20 for separating liquid water W from the gas flow G. The separation device 20 comprises a flow guide contour 22, which directs the gas flow G flowing into the separation chamber 18 frontally onto an inflow surface. The inflow surface is a water guide surface 24, wherein the water guide surface 24 has a contour that defines a drip point 26 for the water W in the direction of a discharge line 28.

[0029] The discharge line 28 has an outer wall 30, with a further water-guiding surface 32 being formed by a section of the outer wall 30 of the discharge line 28. The water W dripping from the water-guiding surface 24 of the separation device 20 thus strikes the water-guiding surface 32 of the discharge line 28 and is guided via the water-guiding surface 32 of the discharge line 28 toward a water-collecting region 36. The liquid water W separated from the gas flow G by the separation device 20 collects in the water-collecting region 36. The discharge line 28 has an inlet opening 34 located in the water-collecting region 36. The water guide surfaces 24, 32 are designed to bring the liquid water W separated from the gas flow G into a dew zone 38 located at the inlet opening 34 of the discharge line 28 in the water collection area 36.This allows icing of the discharge line 28 to be dissolved by means of the water W deliberately brought into the thawing zone 38. After operation of the fuel cell system, water W may remain in the water collection area 36 of the water separator 10, which freezes at low ambient temperatures and can cause the discharge line 28 used to discharge the water W to freeze. Thus, during subsequent commissioning of the fuel cell system, there is a risk that the water W cannot be drained from the water collection area 36 due to the icing of the discharge line 28. When the fuel cell system is commissioned, the water W in the gas flow G heats up by approximately 0.7°C / s to a temperature of 60°C.If, during commissioning of the fuel cell system, the separated water W cannot initially be discharged due to icing of the discharge line 28 in the water collection area 36, ​​the separated warm water W ensures a direct heat input into the thawing zone 38, so that a melt channel leading to the inlet opening 34 of the discharge line 28 quickly forms in the frozen water W. Even if the remainder of the water W in the water collection area 36 is still frozen, newly separated water W can be discharged directly via the melt channel and the discharge line 28. The remaining water W in the water collection area 36 then also thaws during the warm-up phase and can be discharged via the discharge line 28.

[0030] 3 and 4 show a water separator 10 in which the liquid water W separated from the gas flow G is guided via a water guide surface 24 of the separating device 20 and a water guide surface 32 of the discharge line 28 in the direction of a water collection area 36.

[0031] The separation device 20 has a flow guide contour 22, which directs the gas flow G flowing into the separation chamber 18 frontally onto the water guide surface 24. The flow guide contour 22 defines a circulating flow region 40, in which the gas flow G flowing into the water separator 10 via the flow inlet 14 is initially guided in the circumferential direction. The flow guide contour 22 further comprises a cross-sectional taper 42, along which the gas flow G coming from the circulating flow region 40 is converged. The flow guide contour 22 further comprises an alignment channel 44, along which an intended flow direction is imposed on the gas flow G coming from the cross-sectional taper 42.

[0032] The gas flow G flows around the water guide surface 24 and the discharge line 28 within the separation chamber 18 and, after the water has been separated, is led out of the separation chamber 18 again via the flow outlet 16.

[0033] The discharge line 28 is designed as a riser pipe and runs inclined relative to a central axis of the separation chamber 18. The discharge line 28 is connected to a discharge valve (not shown), via which, when actuated, the water W can be discharged from the water collection area 36 via the discharge line 28. When the discharge valve is actuated, water W from the water collection area 36 is sucked into and through the discharge line 28 or pushed into and through the discharge line 28 due to the prevailing pressure conditions.

[0034] Reference symbol

[0035] 10 water separators

[0036] 12 separator housings

[0037] 14 Flow inlet

[0038] 16 Flow outlet

[0039] 18 Separation chamber

[0040] 20 Separation device

[0041] 22 Flow control contour

[0042] 24 Water management area

[0043] 26 Draining point

[0044] 28 Discharge line

[0045] 30 exterior wall

[0046] 32 Water flow area

[0047] 34 Inlet opening

[0048] 36 Water collection area

[0049] 38 dew zone

[0050] 40 Circulating flow area

[0051] 42 Cross-sectional taper

[0052] 44 Alignment channel

[0053] G Gas flow

[0054] W Water

Claims

Claims 1. A water separator (10) for a fuel cell system, comprising a separation device (20) for separating liquid water (W) from a gas flow (G); a water collection region (36) in which the liquid water (W) separated from the gas flow (G) by the separation device (20) collects; and a discharge line (28) for discharging the water (W) located in the water collection region (36), wherein the discharge line (28) has an inlet opening (34) located in the water collection region (36); characterized by one or more water guide surfaces (24, 32) which are designed to bring the liquid water (W) separated from the gas flow (G) into a dew zone (38) located at the inlet opening (34) of the discharge line (28) in the water collection area (36) in order to dissolve an icing of the discharge line (28) by means of the water (W) brought specifically into the dew zone (38).

2. Water separator (10) according to claim 1, characterized in that at least one water guide surface (24) is a component of the separating device (20).

3. Water separator (10) according to claim 2, characterized by a separation chamber (18) into which the gas flow (G) can be introduced, wherein the water guide surface (24) of the separation device (20) is an inflow surface which is arranged in the separation chamber (18) and / or is designed to be flowed against, preferably frontally, by the gas flow (G) flowing into the separation chamber (18).

4. Water separator (10) according to claim 3, characterized in that the separation device (20) has a flow guide contour (22) which is designed to direct the gas flow (G) flowing into the separation chamber (18), preferably frontally, onto the inflow surface.

5. Water separator (10) according to one of claims 2 to 4, characterized in that the water guide surface (24) of the separating device (20) has a contour which specifies one or more drip points (26) for the water (W) in the direction of the dew zone (38).

6. Water separator (10) according to one of the preceding claims, characterized in that at least one water guide surface (32) is a component of the discharge line (28).

7. Water separator (10) according to claim 6, characterized in that the water guide surface (32) of the discharge line (28) is formed by the outer wall (30) of the discharge line (28).

8. Water separator (10) according to one of the preceding claims, characterized in that at least one water guide surface (24, 32) runs at a distance and / or parallel to the discharge line (28).

9. Water separator (10) according to one of the preceding claims, characterized in that the discharge line (28) is designed as a riser pipe.

10. Water separator (10) according to one of the preceding claims, characterized in that the discharge line (28) is connected to a discharge valve, via which the discharge of the water (W) from the water collection area (36) via the discharge line (28) can be initiated by actuation.

11. A fuel cell system comprising at least one fuel cell; a gas circulation path connected to the fuel cell for an anode gas flow to be at least partially recirculated into the fuel cell; and a water separator (10) arranged along the gas circulation path, characterized in that the water separator (10) is designed according to one of the preceding claims.

12. A method for removing liquid water (W) from a gas flow (G), in particular from an anode gas flow of a fuel cell system, by means of a water separator (10), in particular a water separator (10) according to one of claims 1 to 10, comprising the steps: Separating liquid water (W) from the gas flow (G) by means of a separation device (20) of the water separator (10); collecting the water (W) separated from the gas flow (G) by the separation device (20) in a water collection region (36) of the water separator (10); and discharging the water (W) located in the water collection area (36) by means of a discharge line (28) which has an inlet opening (34) located in the water collection area (36), characterized by the step: deliberately bringing the liquid water (W) separated from the gas flow (G) into a dew zone (38) located at the inlet opening (34) of the discharge line (28) in the water collection area (36) by means of one or more water guiding surfaces (24, 32), in order to dissolve an icing of the discharge line (28) by means of the water (W) deliberately brought into the dew zone (38).

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