FUEL CELL SYSTEM WITH AN ANNULAR REFORMER

Abstract

This invention concerns a fuel cell system (100a; 100b; 100c) comprising a fuel cell stack (1) having an anode portion (2) and a cathode portion (3), a reformer (4) for supplying reformed anode gas to the anode portion (2), and an exhaust gas burner (5) for burning anode exhaust gas from the anode portion (2) and/or cathode exhaust gas from the cathode portion (3), wherein the reformer (4) is arranged at least in sections annularly around the exhaust gas burner (5), wherein an inner wall portion of the reformer (4) is arranged completely or at least substantially around an outer wall portion of the exhaust gas burner (5). The invention also concerns a method for operating a fuel cell system conforming to the invention (100a; 100b; 100c) and a motor vehicle (1000) with a fuel cell system conforming to the invention (100a; 100b; 100c).

Claims

1. A fuel cell system comprising a fuel cell stack having an anode portion and a cathode portion, a reformer for supplying reformed anode gas to the anode portion, and an exhaust gas burner for burning at least anode exhaust gas from the anode portion or cathode exhaust gas from the cathode portion, wherein the reformer is arranged at least in sections annularly around the exhaust gas burner, wherein an inner wall portion of the reformer is arranged completely or at least substantially around an outer wall portion of the exhaust gas burner.

2. The fuel cell system according to claim 1, wherein an evaporator for evaporating anode gas is arranged downstream of the exhaust gas burner and upstream of the reformer, and a heat exchanger is arranged downstream of the evaporator, the heat exchanger being arranged on the reformer or in the vicinity of the reformer for heating the reformer or anode gas in the reformer, respectively.

3. The fuel cell system according to claim 1, wherein a starting burner is arranged upstream of the exhaust gas burner.

4. The fuel cell system according to claim 1, wherein the starting burner has a starting burner injector for injecting fuel into the starting burner.

5. The fuel cell system according to claim 1, wherein the exhaust gas burner has an exhaust gas burner catalytic converter, in particular a cylindrical oxidation catalytic converter, for the combustion of at least the anode exhaust gas or the cathode exhaust gas.

6. The fuel cell system according to claim 1, wherein the reformer for reforming the anode gas has a reformer catalytic converter, in particular an annular oxidation catalytic converter, which is arranged at least in sections around at least the exhaust gas burner or the exhaust gas burner catalytic converter.

7. The fuel cell system according to claim 1, wherein the exhaust gas burner for burning at least the anode exhaust gas or the cathode exhaust gas has an exhaust gas burner injector for injecting fuel into the exhaust gas burner.

8. A method of operating a fuel cell system according to claim 3 comprising a starting burner, wherein a sub-stoichiometric fuel-air mixture is combusted in the starting burner in a predefined time window during start operation of the fuel cell system.

9. The method according to claim 8, wherein in the reformer in a predefined time window during a start-up operation of the fuel cell system a sub-stoichiometric fuel-air mixture is burned as part of a catalytic partial oxidation.

10. A motor vehicle having a fuel cell system for supplying power to at least one drive unit of the motor vehicle, the fuel cell system comprising a fuel cell stack having an anode portion and a cathode portion, a reformer for supplying reformed anode gas to the anode portion, and an exhaust gas burner for burning at least anode exhaust gas from the anode portion (2) or cathode exhaust gas from the cathode portion, wherein the reformer is arranged at least in sections annularly around the exhaust gas burner, wherein an inner wall portion of the reformer is arranged completely or at least substantially completely around an outer wall portion of the exhaust gas burner.

Description

[0027] They show schematically in each case:

[0028] FIG. 1 A fuel cell system according to a first embodiment of the present invention,

[0029] FIG. 2 An exhaust gas burner reformer unit with an integrated evaporator in a fuel cell system according to the first embodiment of the present invention,

[0030] FIG. 3 A fuel cell system according to a second embodiment of the present invention,

[0031] FIG. 4 A fuel cell system according to a third embodiment of the present invention, and

[0032] FIG. 5 A motor vehicle equipped with a fuel cell system in accordance with the present invention.

[0033] Elements with the same function and mode of action have the same reference signs in FIGS. 1 to 5.

[0034] FIG. 1 schematically shows a fuel cell system 100a according to a first embodiment. The fuel cell system 100a is configured in the form of a SOFC system and has a fuel source 13 in the form of a fuel tank and an oxygen source 14 in the form of a blower.

[0035] The fuel cell system 110a further comprises a fuel cell stack 1 having an anode portion 2 and a cathode portion 3, a reformer 4 for supplying reformed anode gas to the anode portion 2, and an exhaust gas burner 5 for burning anode exhaust gas from the anode portion 2 and cathode exhaust gas from the cathode portion 3. The reformer 4 is arranged annularly around the exhaust gas burner 5, wherein an inner wall portion of the reformer 4 is arranged entirely or at least substantially entirely around an outer wall portion of the exhaust gas burner 5 (explained in more detail with respect to FIG. 2).

[0036] As shown in FIG. 1, an evaporator 6 for evaporating anode gas is arranged downstream of the exhaust gas burner 5 and upstream of the reformer 4. A heat exchanger 7 is arranged downstream of the evaporator 6, the heat exchanger 7 being arranged on the reformer 4 for heating the reformer 4 or anode gas in the reformer 4. In accordance with the embodiment shown in FIG. 1, exhaust gas from the exhaust gas burner 5 can thus be conveyed directly via the evaporator 6 to the heat exchanger 7 and from there to the surroundings of the fuel cell system 100a.

[0037] Fuel or anode gas can be conveyed from the fuel source 13 via the evaporator 6 to the annular reformer 4 and from there as reformed anode gas to the anode portion 2. Air or an oxygen-containing fluid can be conveyed from the oxygen source 14 via the heat exchanger 7 to the cathode portion 3.

[0038] In FIG. 2 the reformer 4, the exhaust burner 5 and the evaporator 6 are shown schematically according to a preferred embodiment. As can be seen in FIG. 2, the evaporator 6 is arranged directly downstream of the exhaust gas burner 5. Furthermore, FIG. 2 shows that the reformer 4 has an annular reformer catalyst 12 which is arranged corresponding to a passage volume of the reformer 4 in it. It is further represented that the exhaust gas burner 5 for burning the anode exhaust gas and the cathode exhaust gas comprises a cylindrical exhaust gas burner catalyst 11 in the form of an oxidation catalyst arranged corresponding to a passage volume of the exhaust gas burner 5 therein. The exhaust burner catalytic converter 11 and the reformer catalytic converter 12 are only separated from each other by a partition wall of the reformer 4 and the exhaust burner 5 respectively. The reformer catalytic converter 12 is arranged over its entire length around the exhaust burner catalytic converter 11. This enables particularly good heat transfer from the exhaust gas burner 5 or the exhaust gas burner catalyst 11 to the reformer 4 or the reformer catalyst 12.

[0039] With reference to FIG. 3, a fuel cell system 100b is then described according to a second embodiment. The fuel cell system 100b according to the second embodiment essentially corre-sponds to the fuel cell system 100a according to the first embodiment. To avoid a redundant description, only the distinguishing features according to the second embodiment are subsequently described.

[0040] In the fuel cell system 100b shown in FIG. 3, the exhaust gas burner 5 has an exhaust gas burner injector 10 for injecting fuel into the exhaust gas burner 5 for the combustion of the anode exhaust gas and the cathode exhaust gas.

[0041] With reference to FIG. 4, a fuel cell system 100c is then described according to a third embodiment. The fuel cell system 100c according to the third embodiment essentially corre-sponds to the fuel cell system 100a according to the first embodiment and the fuel cell system 100b according to the second embodiment. In order to avoid a redundant description, only the distinguishing features according to the third embodiment are subsequently described.

[0042] In the fuel cell system 100c shown in FIG. 4, a starting burner 8 for heating cathode exhaust gas and anode exhaust gas flowing in the direction of the exhaust gas burner 5 is arranged upstream of the exhaust gas burner 5. The starting burner 8 has a starting burner injector 9 for injecting fuel into the starting burner 8. The starting burner 8 or the starting burner injector 9 can be supplied with fuel from the fuel source 13 and with oxygen, especially air, from the oxygen source 14. For a metered supply of oxygen from the oxygen source 14 to the starting burner 8, a metering valve 15 is arranged in an oxygen line upstream of the starting burner 8 and downstream of the oxygen source 14.

[0043] With reference to FIG. 4, a method for operating the illustrated fuel cell system 100c during a startup process of the fuel cell system 100c is then described.

[0044] When the fuel cell system is started, an oxygen-containing fluid, in particular air, is supplied to the starting burner 8 from the fuel source 13 fuel and from the oxygen source 14. This means that an appropriate fuel-air mixture can be burned in the starting burner 8 to heat the exhaust gas burner 5. During start-up operation of the fuel cell system, a sub-stoichiometric fuel-air mixture is burned in the start burner 8. In a predefined time window during the start-up operation of the fuel cell system 100c, a sub-stoichiometric fuel-air mixture is also combusted in reformer 4 as part of a catalytic partial oxidation. The temperature in the fuel cell system 100c, in particular at the reformer 4, at the exhaust gas burner 5 and/or at the fuel cell stack 1 is determined. As soon as the determined temperature at reformer 4, exhaust gas burner 5 and/or fuel cell stack 1 exceeds a predefined threshold value, the start burner 8 is deactivated. I.e. a supply of fuel and oxygen is stopped.

[0045] FIG. 4 shows a motor vehicle 1000 with a fuel cell system 100a for supplying energy to a drive unit 200 in the form of an electric motor of the motor vehicle 1000.

REFERENCE CHARACTER LIST

[0046] 1 Fuel cell stack [0047] 2 Anode portion [0048] 3 Cathode portion [0049] 4 Reformer [0050] 5 Exhaust burner [0051] 6 Evaporator [0052] 7 Heat exchanger [0053] 8 Start burner [0054] 9 Start burner injector [0055] 10 Exhaust gas burner injector [0056] 11 Exhaust Burner Catalyst [0057] 12 Reformer catalytic converter [0058] 13 Fuel source [0059] 14 Oxygen source [0060] 15 Dosing valve [0061] 100a-100c Fuel cell system [0062] 200 Drive unit [0063] 1000 Motor vehicle