Fuel cell exhaust gas system

Abstract

To substantially prevent fog formation in fuel cell exhaust gas discharged to the periphery by improving a fuel cell exhaust gas system especially for a vehicle.SOLUTION: A fuel cell exhaust gas system especially for a vehicle includes: a first fuel cell exhaust gas cooling unit 30 for accommodating a flow of fuel cell exhaust gas therethrough to dissipate heat from the fuel cell exhaust gas; a first separating unit 34 disposed in a region and / or on the downstream side of the first fuel cell exhaust gas cooling unit 30 and separating condensate held in the fuel cell exhaust gas; and a fuel cell exhaust gas heating unit 36 disposed in a region and / or on the downstream side of the first separating unit and heating the fuel cell exhaust gas.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fuel cell exhaust gas system, via which fuel cell exhaust gases emitted by a fuel cell operated for generating electrical energy, for example in a vehicle, can be released into the environment. [Background technology]

[0002] To generate electrical energy in a fuel cell, hydrogen or a hydrogen-containing gas is supplied to the anode region of the fuel cell, and oxygen or an oxygen-containing gas, such as air, is supplied to the cathode region of the fuel cell. A hydrogen-poor gas is discharged as fuel cell exhaust gas at an anode exhaust gas outlet of the anode region of the fuel cell. An oxygen-poor gas is discharged as fuel cell exhaust gas at a cathode exhaust gas outlet of the cathode region of the fuel cell. Depending on the type of fuel cell, the fuel cell exhaust gas discharged first at the cathode region of the fuel cell or the fuel cell exhaust gas discharged first at the anode region of the fuel cell contains a relatively large proportion of moisture or water vapor. If fuel cell exhaust gas that is significantly rich in water vapor and has a relative humidity in the range of 90 to 100% is discharged into the surroundings via a fuel cell exhaust gas device, the temperature of the fuel cell exhaust gas may drop significantly upon contact with the surrounding air, especially when the ambient temperature is relatively low. This may result in condensation of moisture from the fuel cell exhaust gas and consequently significant mist formation. This type of fog formation can be perceived as unpleasant and undesirable simply based on visual appearance, and can also cause ice to form in the ground underneath the vehicle when the vehicle is stopped in areas where fuel cell exhaust gases escape into the environment, especially when the ambient temperature is very low. Summary of the Invention [Problem to be solved by the invention]

[0003] The object of the present invention is to improve fuel cell exhaust gas systems, in particular for vehicles, so that mist formation in the fuel cell exhaust gases discharged into the environment can be substantially prevented. [Means for solving the problem]

[0004] This problem is solved according to the invention by providing a fuel cell exhaust gas system, in particular for a vehicle, which comprises: a first fuel cell exhaust gas cooling unit through which the fuel cell exhaust gas can flow for extracting heat from the fuel cell exhaust gas; a first separation unit for separating condensate contained in the fuel cell exhaust gas, which is arranged in the region of and / or downstream of the first fuel cell exhaust gas cooling unit; a fuel cell exhaust gas heating unit for heating the fuel cell exhaust gas, which is provided in the region of and / or downstream of the first separation unit; The problem is solved by a fuel cell exhaust gas device comprising:

[0005] In a fuel cell exhaust gas system configured according to the present invention, first cooling the fuel cell exhaust gas and thereby lowering its temperature below the dew point allows some of the moisture or water vapor carried in the fuel cell exhaust gas to separate from the fuel cell exhaust gas and be collected or accumulated as condensate, particularly in a first separation unit. Heating the fuel cell exhaust gas depleted of moisture or water vapor in the fuel cell exhaust gas heating unit does not, of course, cause a change in the amount of water vapor still contained in the fuel cell exhaust gas. However, due to the increase in temperature, the relative humidity in the fuel cell exhaust gas decreases significantly. When the depleted fuel cell exhaust gas is then released into the environment at an elevated temperature, spontaneous condensation or mist formation is prevented. Because the fuel cell exhaust gas mixes sufficiently with the ambient air before its temperature drops significantly again, the resulting dilution prevents significant local mist formation in the area where the fuel cell exhaust gas leaves the fuel cell exhaust gas system.

[0006] For efficient cooling of the fuel cell exhaust gas, the first fuel cell exhaust gas cooling unit may comprise a first heat exchanger that transfers heat from the fuel cell exhaust gas to a cooling medium, preferably a cooling liquid or a cooling gas.

[0007] Similarly, for efficient heating of the fuel cell exhaust gas poor in water vapor, the fuel cell exhaust gas heating unit may be provided with a second heat exchanger and / or at least one electrically excitable heater for transferring heat from the heating medium, preferably a heating liquid or a heating gas, to the fuel cell exhaust gas.

[0008] In order to be able to utilize the heat carried in the fuel cell exhaust gas for an energy-efficient operation of the fuel cell system, it is proposed that the heat transfer medium flowing through the first and second heat exchangers provides a cooling medium and a heating medium, and is thus able to transfer heat from the fuel cell exhaust gas flowing in the further upstream part of the fuel cell exhaust gas device to the fuel cell exhaust gas flowing in the further downstream part of the fuel cell exhaust gas device.

[0009] In an alternative configuration, which also utilizes the heat transported in the fuel cell exhaust gas, a heat exchanger unit can be provided that provides a first and a second heat exchanger, with an upstream heat exchanger area through which the fuel cell exhaust gas can flow and a downstream heat exchanger area downstream of the upstream heat exchanger area that interacts with the upstream heat exchanger area in a heat transfer manner. The heat transfer between the two heat exchanger areas achieves a direct heat transfer that does not require a liquid or gaseous heat transfer medium and is therefore highly efficient.

[0010] In order to be able to remove the moisture condensed after cooling of the fuel cell exhaust gas even during this substantially direct heat transfer, it is proposed that the first separation unit is arranged downstream of the upstream heat exchanger area and upstream of the downstream heat exchanger area.

[0011] For the structural integration of the various system areas of the fuel cell exhaust gas system and therefore for a compact design, it is further proposed that a second fuel cell exhaust gas cooling unit for extracting heat from the fuel cell exhaust gas is provided downstream of the upstream heat exchanger area or / and at the downstream end of this upstream heat exchanger area and upstream of the downstream heat exchanger area or / and at the upstream end of this downstream heat exchanger area. By providing such a second fuel cell exhaust gas cooling unit, in addition to the cooling already achieved in the upstream heat exchanger area, the fuel cell exhaust gas is further cooled upstream of the downstream heat exchanger area, thus supporting condensation of water.

[0012] Here, the second fuel cell exhaust gas cooling unit may comprise a third heat exchanger for transferring heat from the fuel cell exhaust gas to a cooling medium, preferably a cooling liquid or a cooling gas.

[0013] The heat exchanger unit may comprise a heat exchanger unit casing, with the upstream heat exchanger region and the downstream heat exchanger region disposed within the heat exchanger unit casing, and the third heat exchanger may be disposed substantially within the heat exchanger unit casing and / or may be disposed externally surrounding the heat exchanger unit casing.

[0014] For efficient heat transfer for the fuel cell exhaust gas flowing through the various parts of the fuel cell exhaust gas arrangement, the heat exchanger unit may comprise a counter-flow heat exchanger or a cross-flow heat exchanger.

[0015] A first fuel cell exhaust gas line leading to the first fuel cell exhaust gas cooling unit may be provided for conducting the fuel cell exhaust gas to the first fuel cell exhaust gas cooling unit, and thus the first fuel cell exhaust gas line may be a cathode exhaust gas line if moisture or water vapor is mainly contained in the cathode exhaust gas.

[0016] In order to separate the moisture transported in the fuel cell exhaust gas substantially in the form of droplets already upstream of the first fuel cell exhaust gas cooling unit, a second separation unit for separating the liquid contained in the fuel cell exhaust gas substantially in the form of droplets may be arranged in the first fuel cell exhaust gas line.

[0017] The fuel cell exhaust gas device may further comprise a second fuel cell exhaust gas line, preferably an anode exhaust gas line, which either opens into the first fuel cell exhaust gas line or into a fuel cell exhaust gas discharge line directed away from the fuel cell exhaust gas heating unit, meaning that the two associated lines are respectively joined together to join the fuel cell exhaust gas streams directed in the lines. In particular, if the second fuel cell exhaust gas line opens into the first fuel cell exhaust gas line, moisture or water vapor contained in the portion of the fuel cell exhaust gas directed by the second fuel cell exhaust gas line can also be separated.

[0018] In particular, if the fuel cell exhaust gas conducted by the second fuel cell exhaust gas line contains a relatively small proportion of moisture or water vapor, the second fuel cell exhaust gas line may open into the first fuel cell exhaust gas line downstream of the second separation unit.

[0019] In order to prevent residual hydrogen still contained in the anode exhaust gas from being released into the environment in excessively high concentrations, at least one oxidation unit, preferably a catalytic unit or / and a burner, may be provided to oxidize the hydrogen contained in the fuel cell exhaust gas released from the fuel cell.

[0020] If the second fuel cell exhaust gas line, in particular the anode exhaust gas line, leads essentially directly into the fuel cell exhaust gas discharge line, the at least one oxidation unit may be arranged in the second fuel cell exhaust gas line upstream of its opening into the fuel cell exhaust gas discharge line. In particular, if the second fuel cell exhaust gas line leads into the first fuel cell exhaust gas line, the at least one oxidation unit may be arranged in the first fuel cell exhaust gas line downstream of its opening into the first fuel cell exhaust gas line.

[0021] In order to prevent as much as possible the emission of noise generated by the fuel cell system, for example by a compressor, via the fuel cell exhaust gas device, at least one fuel cell exhaust gas silencer may be provided, which is arranged in the fuel cell exhaust gas discharge line that is guided away from the fuel cell exhaust gas heating unit.

[0022] At least one fuel cell exhaust gas silencer is preferably arranged in the second fuel cell exhaust gas line downstream of its opening to the fuel cell exhaust gas discharge line, thereby also suppressing noise transmission via the fuel cell exhaust gas flowing through the second fuel cell exhaust gas line.

[0023] The present invention also relates to a fuel cell system including a fuel cell and a fuel cell exhaust gas device configured according to the present invention, which is arranged in association with the fuel cell.

[0024] In this fuel cell system, the first fuel cell exhaust gas line may be connected to the cathode exhaust gas outlet of the fuel cell, preferably via a cathode exhaust gas blocking unit, and the second fuel cell exhaust gas line may be connected to the anode exhaust gas outlet of the fuel cell, preferably via an anode exhaust gas blocking unit.

[0025] The present invention further relates to a method for operating a fuel cell system, in particular a fuel cell system constructed in accordance with the present invention, which comprises cooling fuel cell exhaust gas discharged from the fuel cell in order to condense the water vapor, and heating the fuel cell exhaust gas, which is depleted in water vapor, after condensing the water vapor.

[0026] The invention will now be described in more detail with reference to the accompanying drawings. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a diagram illustrating the principle of a fuel cell system for a vehicle. [Figure 2] FIG. 2 is a view corresponding to FIG. 1 showing an alternative configuration of the fuel cell system. [Figure 3] 1, showing an alternative configuration of the fuel cell system; FIG. [Figure 4] 1, showing an alternative configuration of the fuel cell system; FIG. [Figure 5] 1, showing an alternative configuration of the fuel cell system; FIG. [Figure 6] 1, showing an alternative configuration of the fuel cell system; FIG. [Figure 7] 1, showing an alternative configuration of the fuel cell system; FIG. [Figure 8] 1, showing an alternative configuration of the fuel cell system; FIG. DETAILED DESCRIPTION OF THE INVENTION

[0028] 1, a fuel cell system for a vehicle is generally designated by the reference numeral 10. The fuel cell system 10 includes a fuel cell 12, configured in the illustrated example as a PEM fuel cell, having an anode region 14 and a cathode region 16. The anode region 14 is supplied with hydrogen or a hydrogen-containing gas W. The cathode region 16 is supplied with oxygen or a gas L containing oxygen and possibly water vapor, such as air.

[0029] A first fuel cell exhaust gas line 22 of the fuel cell exhaust gas system 11 is connected to a cathode exhaust gas outlet 18 of the fuel cell 12 via a cathode exhaust gas shut-off unit 20, such as a valve, an actuating flap or the like, and in the illustrated embodiment, the first fuel cell exhaust gas line 22 is the cathode exhaust gas line. A second fuel cell exhaust gas line 28 of the fuel cell exhaust gas system 11 is connected to an anode exhaust gas outlet 24 of the fuel cell via an anode exhaust gas shut-off unit 26, and in the illustrated embodiment, the second fuel cell exhaust gas line 28 is the anode exhaust gas line.

[0030] The first fuel cell exhaust gas line 22 leads to a first fuel cell exhaust gas cooling unit 30. The first fuel cell exhaust gas cooling unit 30 may comprise a first heat exchanger 32 in which the fuel cell exhaust gas, i.e., the cathode exhaust gas, flowing through the first fuel cell exhaust gas line 22, transfers heat to a liquid or gaseous cooling medium K and is thereby cooled. As a result of this cooling, some of the moisture or water vapor contained in the cathode exhaust gas is condensed in a first separation unit 34 following the first fuel cell exhaust gas cooling unit 30 or collected in this separation unit 34 and can be returned to the fuel cell process, for example, or released in liquid form to the surroundings.

[0031] In a fuel cell exhaust gas heating unit 36 ​​downstream of the first separation unit 34, the fuel cell exhaust gas or cathode exhaust gas poor in water vapor is heated again. This heating can be achieved by transferring heat by means of a heating medium H to the fuel cell exhaust gas flowing through the fuel cell exhaust gas heating unit 36 ​​if the fuel cell exhaust gas heating unit 36 ​​is configured as a second heat exchanger 38. Alternatively or additionally, the fuel cell exhaust gas heating unit 36 ​​can be equipped with an electrically excitable heater 39, which is flowed through by the fuel cell exhaust gas poor in water vapor and transfers heat to this fuel cell exhaust gas.

[0032] The reheated fuel cell exhaust gas, depleted in water vapor, leaves the fuel cell exhaust gas heating unit 36 ​​via a fuel cell exhaust gas discharge line 40, via which the reheated cathode exhaust gas or fuel cell exhaust gas, depleted in water vapor, is discharged to the environment.

[0033] In the fuel cell system 10, in order to prevent noise generated by the operation of, for example, a compressor, etc. from being transmitted to the surrounding area via the fuel cell exhaust gas, a fuel cell exhaust gas muffler 42 may be provided in the fuel cell exhaust gas discharge pipe 40, and the fuel cell exhaust gas muffler 42 may have one or more chambers and / or one or more resonator chambers connected to each other and through which the fuel cell exhaust gas can flow, similar to a muffler arranged corresponding to an internal combustion engine, for example.

[0034] The anode exhaust gas discharged as fuel cell exhaust via the anode exhaust outlet 24 generally still contains a residual hydrogen content. The concentration of hydrogen still contained in the anode exhaust gas may be so high that discharge to the environment is not permitted. Therefore, a catalytic unit 44, which forms an example of an oxidation unit, may be arranged in the second fuel cell exhaust gas line 28. In this catalytic unit 44, the residual hydrogen contained in the anode exhaust gas is oxidized with oxygen supplied via a supply line 46. Air, for example, can be introduced into the second fuel cell exhaust gas line 28 via the supply line 46.

[0035] In the fuel cell system 10 shown in FIG. 1 , the portion of the fuel cell exhaust gas discharged from the fuel cell 12 via the first fuel cell exhaust gas line 22, i.e., the cathode exhaust gas, is first cooled to remove a portion, particularly most, of the water vapor contained in this cathode exhaust gas. Due to its relatively low temperature, the fuel cell exhaust gas, which is poor in water vapor, has a high relative humidity, which can approach 100%. By heating this fuel cell exhaust gas, which is poor in water vapor but has a high relative humidity, in the fuel cell exhaust gas heating unit 36, the relative humidity of the fuel cell exhaust gas is reduced, so that the fuel cell exhaust gas discharged to the environment via the fuel cell exhaust gas discharge line 40 has a relative humidity significantly lower than 100%. Subsequently, spontaneous mist formation due to condensation of water is prevented when the discharged fuel cell exhaust gas comes into contact with relatively cool ambient air or with a relatively cool object around the vehicle. This is because, before the temperature of the fuel cell exhaust gases released into the environment drops below the dew point, they are mixed relatively strongly with the ambient air, and thus the fuel cell exhaust gases are diluted relatively strongly.

[0036] An alternative embodiment of a fuel cell system 10 is illustrated in Figure 2. The fuel cell system 10 illustrated in Figure 2 has various modifications compared to the fuel cell system illustrated in Figure 1, which may be implemented individually or in combination as specifically illustrated in Figure 2.

[0037] 2, it can first be seen that the second fuel cell exhaust gas line 28 opens into the first fuel cell exhaust gas line 22. This means that the fuel cell exhaust gas discharged via the second fuel cell exhaust gas line 28, i.e., the anode exhaust gas in the illustrated example, is also led to the first fuel cell exhaust gas cooling unit 30 and the fuel cell exhaust gas heating unit 36. This allows the moisture or water vapor contained in the anode exhaust gas to be condensed or collected in the first separation unit 34.

[0038] In this embodiment, a catalytic unit 44 may also be disposed in the first fuel cell exhaust gas line 22 to oxidize residual hydrogen contained in the anode exhaust gas. Alternatively or additionally, a catalytic unit 44' may be disposed in the fuel cell exhaust gas discharge line 40. Disposing the catalytic unit 44 upstream of the first fuel cell exhaust gas cooling unit 30 has the important advantage that the fuel cell exhaust gas conducted by the catalytic unit 44 has a relatively high temperature, which contributes to efficient operation of the catalytic unit 44. Positioning the catalytic unit 44' in the fuel cell exhaust gas discharge line has the advantage that the fuel cell exhaust gas flowing through the catalytic unit 44' contains a relatively low proportion of water or water vapor, which contributes to relatively little aging of the catalytic unit 44'. The oxygen required for hydrogen oxidation can be provided by the residual oxygen contained in the cathode exhaust gas, so additional introduction of oxygen or air is not required.

[0039] 2, it can further be seen that a second separation unit 48 is arranged in the first fuel cell exhaust gas line 22, for example upstream with respect to the catalyst device 44. In the illustrated embodiment, the second separation unit 48 already allows a portion of the water carried by the cathode exhaust gas, particularly in the form of droplets, to be removed from the cathode exhaust gas, so that the catalyst unit 44, which is positioned upstream of the first fuel cell exhaust gas cooling unit 30 and the first separation unit 34, is also passed through by the fuel cell exhaust gas which already contains a reduced proportion of water or water vapor.

[0040] 3 shows a modified configuration of the fuel cell system 10, particularly in the region of the first fuel cell exhaust gas cooling unit 30 and the fuel cell exhaust gas heating unit 36. In this configuration, in the first fuel cell exhaust gas cooling unit 30 configured as a first heat exchanger 32, heat is removed from the fuel cell exhaust gas flowing therethrough by a heat transfer medium M, which is also conducted, for example in a closed circuit, by a fuel cell exhaust gas heating unit 36 ​​configured as a second heat exchanger 38. Thus, the fuel cell exhaust gas flowing further downstream in the fuel cell exhaust gas device 11 can be heated by the fuel cell exhaust gas flowing further upstream in the fuel cell exhaust gas device 11. Alternatively or additionally, in the fuel cell exhaust gas heating unit 36, the fuel cell exhaust gas flowing therethrough can be heated by a heating medium H and / or an electrically excitable heater 39.

[0041] In order to be able to further cool the fuel cell exhaust gas, a second fuel cell exhaust gas cooling unit 50 is arranged downstream of the first fuel cell exhaust gas cooling unit 30. This second fuel cell exhaust gas cooling unit 50 can, for example, have a third heat exchanger 52 in which the fuel cell exhaust gas already cooled in the first fuel cell exhaust gas cooling unit 30 can transfer heat to the cooling medium K. As already mentioned above, the water is condensed in the first separation unit 34, so that the fuel cell exhaust gas, which is depleted in water vapor, flows in the direction towards the fuel cell exhaust gas heating unit 36 ​​that follows downstream.

[0042] A variant that is particularly advantageous in terms of efficient heat transfer and simple construction, in which the heat contained in the fuel cell exhaust gas is uniformly utilized to heat the portion of the fuel cell exhaust gas that flows further downstream, is shown in Fig. 4. The embodiment of the fuel cell exhaust gas system 11 shown in Fig. 4 is provided with a heat exchanger unit, designated as a whole by the reference numeral 54, which in the illustrated example is configured as a counterflow heat exchanger. The heat exchanger unit 54 has an upstream heat exchanger area 56 that provides the first fuel cell exhaust gas cooling unit 30 or the first heat exchanger 32.

[0043] The heat exchanger unit 54 further comprises a downstream heat exchanger region 58 which serves the fuel cell exhaust gas heating unit 36 ​​or the second heat exchanger 38. Both heat exchanger regions 56, 58 are formed in a heat exchanger unit casing 60 of the heat exchanger unit 54 like channels and may be separated from one another by one or more separating walls 62 to provide flow paths through which the fuel cell exhaust gas flows in substantially counter-directions, thereby transferring heat from the portion of the fuel cell exhaust gas flowing through the upstream heat exchanger region 56 to the portion of the fuel cell exhaust gas flowing through the downstream heat exchanger region 58.

[0044] In this configuration too, it is suggested that in the fuel cell exhaust gas heating unit 36, i.e. the downstream heat exchanger area 58, the fuel cell exhaust gas flowing through this downstream heat exchanger area 58 may be additionally heated by a heating medium and / or an electrically excitable heater, as described above.

[0045] The fuel cell exhaust gas that has flowed through the upstream heat exchanger area 56 and has left it is led downstream to the second fuel cell exhaust gas heating unit 50 or third heat exchanger 52 that follows the upstream heat exchanger area 56, where it dissipates heat into the cooling medium K and is thus further cooled. In the first separation unit 34, water condensed from the fuel cell exhaust gas due to the further cooling is collected. The water vapor-depleted fuel cell exhaust gas then flows further to the downstream heat exchanger area 58, where it is heated by thermal interaction with the fuel cell exhaust gas flowing through the downstream heat exchanger area 56 and, if necessary, additionally by a heating medium and / or an electrically excitable heater.

[0046] 5 shows a configuration variant in which the second fuel cell exhaust gas cooling unit 50 and the first separation unit 34 are structurally integrated with a heat exchanger unit 54. As can be seen in FIG. 5, the third heat exchanger 52 of the second fuel cell exhaust gas cooling unit 50 can be integrated into the upstream heat exchanger section 56, in particular at its downstream end 64. At this downstream end 64 of the upstream heat exchanger section 56 or downstream, the flow transition to and from the first separation unit 34 to the downstream heat exchanger section 58 takes place. Moisture collected in the first separation unit 34, and thus also in the heat exchanger unit casing 60 of the heat exchanger unit 54, can be released to the environment or returned to the fuel cell process, for example, via a shut-off unit 66.

[0047] For highly efficient heat transfer, the third heat exchanger 52 may have ribs that increase the surface area available for thermal interaction with the fuel cell exhaust gas flowing through the upstream heat exchanger region 56.

[0048] 6 shows a variant of the construction principle shown in Fig. 5 in which the second fuel cell exhaust gas cooling unit 50 is integrated into the upstream heat exchanger area 56, in particular in the region of its downstream end 64, and into the upstream heat exchanger area 58, in particular at its upstream end 68. Thus, in the entire transition area from the upstream heat exchanger area 56, i.e. the first fuel cell exhaust gas cooling unit 30, to the downstream heat exchanger area 58, i.e. the fuel cell exhaust gas heating unit 36, cooling of the fuel cell exhaust gas allows moisture or water vapor to condense and be stored or collected in the first separation unit 34.

[0049] In this configuration, too, for highly efficient heat transfer, the third heat exchanger 52 may have ribs that increase the surface available for thermal interaction with the fuel cell exhaust gas flowing through the upstream heat exchanger region 56. It is further suggested that, in this embodiment, additional heating of the fuel cell exhaust gas flowing through the downstream heat exchanger region 58 may be achieved by a heating medium and / or an electrically excitable heater.

[0050] 7 of the fuel cell exhaust gas system 11, heat is also removed from the fuel cell exhaust gas in the heat exchanger unit 54 in the region of the downstream end 64 of the upstream heat exchanger section 56 and in the region of the upstream end 66 of the downstream heat exchanger section 58. For this purpose, the first heat exchanger 32 of the first fuel cell exhaust gas cooling unit 30 surrounds with its outer surface a heat exchanger unit casing 60 of the heat exchanger unit 54, through which a cooling medium K can flow. To enhance the thermal interaction and thus improve the heat removal from the fuel cell exhaust gas flowing through the heat exchanger unit 54, heat transfer ribs 70 can be provided on the outer surface of the heat exchanger unit casing 60, which increase the surface area available for heat removal into the cooling medium K.

[0051] 8 shows another alternative configuration in which heat can be transferred in a heat exchanger unit 54 from the fuel cell exhaust gas flowing in a further upstream part of the fuel cell exhaust gas device 11 to the fuel cell exhaust gas flowing in a further downstream part of the fuel cell exhaust gas device 11. In this embodiment, the heat exchanger unit 54 is configured as a cross-flow heat exchanger. A volume is formed in the heat exchanger unit casing 60, which essentially provides an upstream heat exchanger area 56, through which the fuel cell exhaust gas supplied via the first fuel cell exhaust gas line 22 flows. The fuel cell exhaust gas guided by this upstream heat exchanger area 56 then flows through the second fuel cell exhaust gas cooling unit 50 or its third heat exchanger 52, and in the process releases heat to the cooling medium K. After passing through the first separation unit 34, the water vapor-depleted fuel cell exhaust gas then flows through a duct area extending within the heat exchanger unit casing 60, which provides a downstream heat exchanger area 58, which may be provided with heat transfer ribs 72 for amplified thermal interaction with the fuel cell exhaust gas passing through the upstream heat exchanger area 56.

[0052] In this embodiment, the fuel cell exhaust gas also heats and exits the upstream heat exchanger region 58 or heat exchanger unit 54, and then flows to, for example, the catalyst unit 44' and muffler 42 before being released into the surroundings heated and therefore with a relatively low relative humidity.

[0053] 7 and 8, the aforementioned means may also be additionally assigned to the downstream heat exchanger area 58 for additional heating, i.e., the water vapor-depleted fuel cell exhaust gas flowing through the downstream heat exchanger area 58 may be additionally heated by a heating medium and / or an electrically excitable heater.

[0054] In all of the above-described embodiments, the cooling medium K and / or the heating medium H, if used, can be a liquid or a gas. In particular, the cooling medium K can release the heat it absorbs to the surroundings in a separate heat exchanger. The cooling medium K can be, for example, ambient air, and the first heat exchanger can have ribs around which the ambient air can flow. The heating medium H can be heated, for example, in a catalytic oxidation process taking place in the catalytic unit 44 or 44′. Alternatively, a burner can be provided as another example of an oxidation unit instead of or in addition to such a catalytic unit for oxidizing the residual hydrogen still contained in the anode exhaust gas. In the burner, the residual hydrogen is burned with oxygen, for example, the residual oxygen contained in the cathode exhaust gas. The heat generated in this process can be transferred to the heating medium H in a heat exchanger associated with the burner and from there to the fuel cell exhaust gas flowing through the second heat exchanger 38.

[0055] In a fuel cell exhaust gas system constructed according to the invention, as shown in particular in the embodiments shown in Figures 4 to 7, various system areas, in particular the first fuel cell exhaust gas cooling unit, the first separation unit and the fuel cell exhaust gas heating unit, and possibly the second fuel cell exhaust gas cooling unit, can be structurally combined or fused together, so that these various system areas can be directly connected to one another or can overlap one another in terms of fluid technology. Thus, by means of the first separation unit, water vapor or moisture can already be separated from the fuel cell exhaust gas in the region of the first fuel cell exhaust gas cooling unit and / or in the region of the fuel cell exhaust gas heating unit and collected, for example in liquid form.

[0056] It should be noted that the above-described structure of the fuel cell exhaust gas device can also or alternatively be used in fuel cells operating according to a different functional principle, in which a relatively large proportion of water or water vapor is generated in the anode region and is discharged from the fuel cell via the anode exhaust gas. In such a case, for example, the first fuel cell exhaust gas line can be connected to the anode exhaust gas outlet of the fuel cell, and the second fuel cell exhaust gas line can be connected to the cathode exhaust gas outlet of the fuel cell.

Claims

1. A fuel cell exhaust gas device, a first fuel cell exhaust gas cooling unit (30) through which the fuel cell exhaust gas can flow in order to extract heat from the fuel cell exhaust gas; a first fuel cell exhaust gas line (22) leading to said first fuel cell exhaust gas cooling unit (30), said first fuel cell exhaust gas line (22) being a cathode exhaust gas line; a first separation unit (34) arranged in the region of and / or downstream of said first fuel cell exhaust gas cooling unit (30) for separating the condensate contained in said fuel cell exhaust gas; a fuel cell exhaust gas heating unit (36) in the region of and / or downstream of the first separation unit (34) for heating the fuel cell exhaust gas; Including, - said first fuel cell exhaust gas cooling unit (30) comprises a first heat exchanger (32) for cooling said fuel cell exhaust gas, - said fuel cell exhaust gas heating unit (36) comprises a second heat exchanger (38) for heating said fuel cell exhaust gas, - providing the first heat exchanger (32) and the second heat exchanger (38), a heat exchanger unit (54) is provided which is designed as a counter-flow or cross-flow heat exchanger, said heat exchanger unit (54) comprising an upstream heat exchanger area (56) through which the fuel cell exhaust gas can flow and a downstream heat exchanger area (58) downstream of said upstream heat exchanger area (56) which interacts in a heat transfer manner with said upstream heat exchanger area (56), a second fuel cell exhaust gas cooling unit (50) is provided downstream of the upstream heat exchanger area (56) or / and at the downstream end (64) of the upstream heat exchanger area (56) and upstream of the downstream heat exchanger area (58) or / and at the upstream end (68) of the downstream heat exchanger area (58) for extracting heat from the fuel cell exhaust gas, - said second fuel cell exhaust gas cooling unit (50) comprises a third heat exchanger (52) for transferring heat from said fuel cell exhaust gas to a cooling medium (K), the heat exchanger unit (54) comprises a heat exchanger unit casing (60), the upstream heat exchanger area (56) and the downstream heat exchanger area (58) are arranged in the heat exchanger unit casing (60), and the third heat exchanger (52) is arranged in the heat exchanger unit casing (60) and / or is arranged to surround the heat exchanger unit casing (60) on the outside, Fuel cell exhaust system.

2. 2. The fuel cell exhaust system of claim 1, wherein the fuel cell exhaust heating unit (36) comprises at least one electrically excitable heater (39).

3. 3. The fuel cell exhaust gas system according to claim 1, wherein the first separation unit (34) is arranged downstream of the upstream heat exchanger area (56) and upstream of the downstream heat exchanger area (58).

4. 3. The fuel cell exhaust gas system according to claim 1, wherein a second separation unit (48) is associated with the first fuel cell exhaust gas line (22) for separating liquid contained in the fuel cell exhaust gas in droplet form.

5. 3. The fuel cell exhaust gas system according to claim 1, further comprising a second fuel cell exhaust gas line (28) which opens into the first fuel cell exhaust gas line (22) or into a fuel cell exhaust gas discharge line (40) which is guided in a direction away from the fuel cell exhaust gas heating unit (36).

6. 6. The fuel cell exhaust system of claim 5, wherein the second fuel cell exhaust line (28) is an anode exhaust line.

7. 6. The fuel cell exhaust gas system according to claim 5, wherein a second separation unit (48) for separating liquid contained in the fuel cell exhaust gas in droplet form is associated with the first fuel cell exhaust gas line (22), and the second fuel cell exhaust gas line (28) opens into the first fuel cell exhaust gas line (22) downstream of the second separation unit (48).

8. 3. The fuel cell exhaust gas system according to claim 1, further comprising at least one oxidation unit for oxidizing hydrogen contained in the fuel cell exhaust gas.

9. 9. The fuel cell exhaust gas system of claim 8, wherein the at least one oxidation unit includes a catalytic unit (44, 44') or / and a burner.

10. a second fuel cell exhaust gas line (28) is provided, the second fuel cell exhaust gas line (28) opening into a fuel cell exhaust gas discharge line (40) guided away from the first fuel cell exhaust gas line (22) or the fuel cell exhaust gas heating unit (36); 9. The fuel cell exhaust gas system according to claim 8, wherein at least one oxidation unit is arranged in the second fuel cell exhaust gas line (28) upstream of its opening into the fuel cell exhaust gas discharge line (40), and / or at least one oxidation unit is arranged in the first fuel cell exhaust gas line (22) downstream of its opening of the second fuel cell exhaust gas line (28) into the first fuel cell exhaust gas line (22).

11. 3. The fuel cell exhaust gas system according to claim 1, further comprising at least one fuel cell exhaust gas muffler (42) arranged in a fuel cell exhaust gas discharge line (40) that is guided away from the fuel cell exhaust gas heating unit (36).

12. a second fuel cell exhaust gas line (28) is provided, the second fuel cell exhaust gas line (28) opening into a fuel cell exhaust gas discharge line (40) guided away from the first fuel cell exhaust gas line (22) or the fuel cell exhaust gas heating unit (36); 12. The fuel cell exhaust gas system according to claim 11, wherein at least one fuel cell exhaust gas muffler (42) is arranged downstream of the opening of the second fuel cell exhaust gas line (28) into the fuel cell exhaust gas discharge line (40).

13. 3. A fuel cell system comprising: a fuel cell (12); and a fuel cell exhaust gas device (11) according to claim 1 or 2, arranged in association with the fuel cell.

14. a second fuel cell exhaust gas line (28) is provided, the second fuel cell exhaust gas line (28) opening into a fuel cell exhaust gas discharge line (40) guided away from the first fuel cell exhaust gas line (22) or the fuel cell exhaust gas heating unit (36); 14. The fuel cell system of claim 13, wherein the first fuel cell exhaust gas line (22) is connected to a cathode exhaust gas outlet (18) of the fuel cell (12), and the second fuel cell exhaust gas line (28) is connected to an anode exhaust gas outlet (24) of the fuel cell (12).

15. 15. The fuel cell system of claim 14, wherein the first fuel cell exhaust gas line (22) is connected to a cathode exhaust gas outlet (18) of the fuel cell (12) via a cathode exhaust gas shutoff unit (20), and the second fuel cell exhaust gas line (28) is connected to an anode exhaust gas outlet (24) of the fuel cell (12) via an anode exhaust gas shutoff unit (26).

Images