EP2040831A2

EP2040831A2 - Reformer for a fuel cell system and method for operating said reformer

Info

Publication number: EP2040831A2
Application number: EP07764384A
Authority: EP
Inventors: Matthias Boltze; Michael Rozumek; Stefan Käding; Manfred Pfalzgraf; Andreas Engl; Beate Bleeker; Michael Süßl; Markus Bedenbecker
Original assignee: Enerday GmbH
Current assignee: Enerday GmbH
Priority date: 2006-07-13
Filing date: 2007-06-19
Publication date: 2009-04-01
Also published as: WO2008006331A3; JP2009543303A; BRPI0714206A2; WO2008006331A2; KR20090017698A; CA2657502A1; EA200970026A1; CN101489664A; AU2007272139A1; US20100212977A1; DE102006032469B4; DE102006032469A1

Abstract

The invention relates to a reformer (12) for a fuel cell system (10). Said reformer comprises an oxidation zone (48) to which stored fuel can be supplied by means of a primary fuel supply device (50; 62) for reaction with an oxidant; and a mixing zone (54), arranged downstream of the oxidation zone (48), to which stored fuel can be supplied by means of a secondary fuel supply device (56; 64) for mixing with substances originating from the oxidation zone (48). The invention is characterized in that the primary fuel supply device (50; 62) and the secondary fuel supply device (56; 64) are adapted to supply fuel in such a manner that the fuel supplied by the primary fuel supply device (50; 62) differs from the fuel supplied by the secondary fuel supply device (56; 64) with respect to the type of fuel and/or its state of aggregation and/or the pressure and/or the temperature at which it is supplied. The invention also relates to a fuel cell system comprising said reformer, to a motor vehicle comprising said fuel cell system and to a method for operating said reformer (12).

Description

Reformer for a fuel cell system and method of operating a reformer

The invention relates to a reformer for a fuel cell system, comprising an oxidation zone, which stored fuel is fed by means of a primary Brennstoffzuführ- device for reaction with Ox dationsmittel; and a mixing zone arranged downstream of the oxidation zone, which stored fuel can be supplied by means of a secondary fuel supply means for mixing with emerging from the oxidation zone substances.

Moreover, the invention relates to a fuel cell system with such a reformer and a motor vehicle with such a fuel cell system.

The invention further relates to a method for operating a reformer of a fuel cell system, comprising the steps of: supplying fuel located in a fuel tank to an oxidation zone in which the fuel with oxidant is convertible; and supplying fuel in a fuel tank to a mixing zone located downstream of the oxidation zone in which the fuel is miscible with materials exiting the oxidation zone.

Fuel cell systems are used to convert chemical energy into electrical energy. The key element in such systems is a fuel cell in which electrical energy is released by the controlled conversion of hydrogen and oxygen. Fuel- _ _

Line systems must be able to process common fuels in practice. Since hydrogen and oxygen are converted in a fuel cell, the fuel used must be prepared in such a way that the gas supplied to the anode of the fuel cell has the highest possible proportion of hydrogen - this is the task of the reformer. For this purpose, a reformer fuel and oxidizing agent, preferably air, fed. In the reformer then takes place an implementation of the fuel with the oxidant. The reformate generated by means of the reformer is fed to the fuel cell or to a fuel cell stack, electric energy being released by the controlled conversion of hydrogen as a constituent of the reformate and oxidizing agent. A generic reformer is known from DE 103 59 205 Al.

Object of the present invention is the generic reformer, the generic fuel cell system, the generic motor vehicle and the generic

Further develop a method for operating a reformer such that an optimized operation of the reformer can be achieved.

This object is solved by the independent claims.

Advantageous embodiments and modifications of the invention will become apparent from the dependent claims.

The reformer according to the invention is based on the state of the art in that the primary fuel feed device and the secondary fuel feed device are designed to feed fuel in such a way that the fuel feed from the primary fuel feed device _, _

supplied fuel from the fuel supplied from the secondary fuel supply means in terms of fuel grade and / or state of aggregation and / or supply pressure and / or supply temperature differs. The invention is based on the finding that different requirements are placed on the quality of the evaporation in the oxidation zone and the mixing zone. In the oxidation zone, it is sufficient if the fuel evaporates so well that a homogeneous combustion takes place and accordingly a homogeneous gas mixture enters the mixing zone. By contrast, in the mixing zone, the requirements for evaporation are higher. There, it must be possible to achieve homogeneous evaporation, and at the same time, the fuel vapor must mix homogeneously with the gas mixture from the oxidation zone. Advantageously, the present invention solves this by the fact that the fuel supplied from the primary fuel supply device differs from the fuel supplied by the secondary fuel supply device in terms of fuel grade and / or state of aggregation and / or feed pressure and / or feed temperature. This has the advantage over the prior art that these parameters can be selected and adapted in such a way that optimum starting conditions are obtained for the respective evaporation in the corresponding zone. This has the further advantage of widening the performance modality, ie the work area, of the reformer because the reformer can be operated in an improved manner. In practice, a fuel of one type of fuel (eg diesel) can thus be burned in the oxidation zone of the reformer, whereas a fuel of another type of fuel (eg gasoline) is mixed in the mixing zone as educt for the reforming in the product gas from the Oxidationszonenverbrennung. _- _-

The reformer according to the invention can advantageously be further developed in that the primary fuel feed device is a low-pressure feed device with a feed pressure of at most 10 bar and the secondary fuel feed device is a high-pressure feed device with a feed pressure of more than 50 bar. The fact that the requirements for the evaporation in the mixing zone are higher, the use of a more expensive Hochdruckzuführsystems is advantageous here. By contrast, in the oxidation zone, it is sufficient to use a more cost-effective low-pressure feed system. In addition to saving energy, this would also have the advantage that costs can be saved by dispensing with a significantly expensive high-pressure feed for the oxidation zone.

In particular, it is provided in this connection that the secondary fuel supply device is a high-pressure supply device with a supply pressure of 50 to 100 bar.

Alternatively it can be provided that the secondary fuel supply device is a high-pressure supply device with a supply pressure of 900 to 1100 bar.

Further, the reformer according to the invention may be further developed in that the primary fuel supply means is adapted to be connected to a first fuel tank, and the secondary fuel supply means is adapted to be connected to a separate second fuel tank. Due to the different evaporation temperatures, enthalpies and velocities of different types of fuel, supplying the oxidation zone and the mixing zone with different types of fuel makes it possible to vary the fuel grade. be selected that in the respective zone, the evaporation and the associated implementation proceeds optimally.

Furthermore, the invention provides a fuel cell system and a motor vehicle with such a fuel cell system, which deliver the advantages described above in a transferred manner.

The generic method can advantageously be further developed in that the fuel supplied to the oxidation zone differs from the fuel supplied to the mixing zone in terms of fuel grade and / or state of aggregation and / or feed pressure and / or feed temperature. Within the scope of the method according to the invention, the invention is also based on the finding that different requirements are placed on the quality of the evaporation in the oxidation zone and the mixing zone. In the oxidation zone, it is sufficient if the fuel evaporates so well that a homogeneous combustion takes place and accordingly a homogeneous gas mixture enters the mixing zone. By contrast, in the mixing zone, the requirements for evaporation are higher. There, it must be possible to achieve a homogeneous evaporation, and at the same time, the fuel vapor must mix homogeneously with the gas mixture from the oxidation zone. Advantageously, the present invention solves this by the fact that the fuel supplied from the primary fuel supply device differs from the fuel supplied by the secondary fuel supply device with regard to fuel grade and / or aggregate state and / or feed pressure and / or feed temperature. This has the advantage over the prior art that these parameters can be selected and adapted in such a way that optimum starting conditions for the respective evaporation in the corresponding _ _

resulting in a speaking zone. This has the further advantage that the power modularity, i. The scope of work of the reformer is broadened because the reformer can be operated in an improved way. In practice, therefore, one fuel of one type of fuel (e.g., diesel) may be burned in the oxidation zone of the reformer, whereas a fuel of another type of fuel (e.g., gasoline) is mixed in the mixing zone as a reactant for reforming into the product gas from the oxidation zone combustion.

Furthermore, the inventive method can be further developed in that the fuel supplied to the oxidation zone with a supply pressure of at most 10 bar and the fuel supplied to the mixing zone with a feed pressure of more than 50 bar is supplied.

In particular, it is provided that the fuel supplied to the mixing zone is supplied with a feed pressure of 50 to 100 bar.

Alternatively, it may be provided that the fuel supplied to the mixing zone is supplied at a feed pressure of 900 to 1100 bar.

In addition, the method according to the invention can be developed such that the fuel supplied to the oxidation zone is supplied from a first fuel tank and the fuel supplied to the mixing zone is fed from a separate second fuel tank. Due to the different vaporization temperatures, enthalpies and velocities of different types of fuel, supplying the oxidation zone and the mixing zone with different fuel types makes it possible to vary the fuel grade. _ _

be selected that in the respective zone, the evaporation and the associated implementation proceeds optimally.

Preferred embodiments of the invention will be described below by way of example with reference to the accompanying drawings.

Show it:

Figure 1 is a schematic representation of a fuel cell system according to a first embodiment;

Figure 2 is a schematic representation of a reformer GE measure the first embodiment;

Figure 3 is a schematic representation of a fuel cell system according to a second embodiment; and

Figure 4 is a schematic representation of a reformer according to the second embodiment.

FIG. 1 shows a schematic representation of a fuel cell system according to a first exemplary embodiment. The fuel cell system 10 installed in a motor vehicle comprises a reformer 12, to which fuel is supplied via a first fuel line 14 from a first fuel tank 16. Furthermore, the fuel is supplied to the reformer 12 from a second fuel tank 20 by means of a second fuel train 18. Suitable fuel types are diesel, gasoline, biogas, natural gas and other types of fuel known from the prior art. In the context of the first embodiment differs _ _

If, for example, the fuel grade in the first fuel tank 16 is of the fuel grade in the second fuel tank 20, then it is advantageous to have gasoline in the first fuel tank 16 and gasoline in the second fuel tank 20. Furthermore, the reformer 12 is oxidized via a first oxidant strand 22 , For example, air supplied. The reformate produced by the reformer 12 is fed to a fuel cell stack 26 via a reformate train 24. The reformate is a hydrogen-containing gas which is converted in the fuel cell stack 26 by means of cathode feeds conveyed via a cathode feed line 28, with the generation of electricity and heat. The generated power can be tapped off via electrical connections 30. In the illustrated case, the anode exhaust gas via an anode exhaust gas strand 32 a

Mixing unit 34 of an afterburner 36 supplied. The afterburner 36 can be supplied with fuel from the first fuel tank 16 via a third fuel line 38. Further, the afterburner 36 via a second oxidant medium strand 40 oxidizing agent can be supplied. In the afterburner 36, a conversion of the depleted anode exhaust gas with the conveyed fuel and oxidizing agent to a combustion exhaust gas, which is mixed in a mixing unit 42 with cathode exhaust air, which is conveyed via a cathode exhaust air 44 from the fuel cell stack 26 to the mixing unit 42. The combustion exhaust gas, which contains virtually no pollutants, flows through a heat exchanger 46 for preheating the cathode feed air and finally leaves the fuel cell system 10.

Figure 2 shows a schematic representation of the reformer according to the first embodiment. The reformer 12 prescribes an oxidation zone 48, which can be supplied with fuel to a primary fuel feed device 50. _ _

The fuel supply device 50 is connected to the first fuel train 14, so that the primary fuel supply device 50, the fuel is supplied, which is stored in the first fuel tank 16. Furthermore, an oxidant supply device 52 connected to the first oxidant strand 22 is provided, by means of which oxidizing agent can be fed to the oxidation zone 48. Within the oxidation zone 48, conversion of fuel and oxidant takes place in a combustion or exothermic, complete oxidation reaction. The resulting hot Produktgasström then occurs downstream, ie right in Fig. 2 in a mixing zone 54 a. The individual zones of the reformer are diagrammatically separated from one another in FIG. 2 by dashed lines. The zones may be separated by structural features or blended into each other. In the mixing zone 54, additional fuel is added to the resulting product gas stream by means of a secondary fuel supply device 56. In the present example, the primary and secondary fuel supply means 50, 56 are respectively an injection nozzle and preferably a Venturi nozzle, however, the fuel may also be supplied to the oxidation zone 48 and the mixing zone 54, respectively, by means of an evaporation type fuel supply having a porous evaporation unit. The secondary fuel supply device 56 is connected to the second fuel strand 18, so that in the second fuel tank 20 stockpiled fuel from a different fuel type than in the first fuel tank 16, the secondary fuel feed means 56 can be fed. In addition, it can be provided that the mixing zone 54 is supplied with oxidizing agent. The mixed with the additional fuel gas mixture enters a reforming zone 58, where it is in an endothermic reaction in a hydrogen-rich - -

Gas mixture is reacted, preferably by means of a catalyst arranged there. This reformate, i. hydrogen-rich gas mixture leaves the reformer 12 via the Reformatstrang 24 and is available for further use for the fuel cell stack 26.

In a modification of the first embodiment, fuel of the same fuel grade is stored in the first fuel tank 16 and the second fuel tank 20, but differs in its aggregate state (i.e., gaseous, liquid). In this case, for example, one fuel can be present in liquid form in one of the fuel tanks and fuel in the other fuel tank can be present in a gaseous state, which is achieved in that both in one

Fuel tank as well as in the associated fuel strands higher pressure than in the other fuel strands, which retains the fuel in a gaseous state.

Reference numerals, which are identical to those used in the first embodiment below, identify identical elements with the same functionality for the first embodiment, the description of which is omitted to avoid repetition.

FIG. 3 shows a schematic representation of a fuel cell system according to a second exemplary embodiment. The fuel cell system 10 of the second embodiment differs from the fuel cell system shown in FIG. 1 in that instead of the first and second fuel tanks 16 and 20, only a single fuel tank 60 is installed in the vehicle. This fuel tank 60 supplies the first, second and third - -

Fuel strands 14, 18 and 38 with fuel of the same type of fuel.

FIG. 4 shows a schematic representation of a reformer according to the second exemplary embodiment. The reformer 12 of the second embodiment has, instead of the primary fuel supply means of Fig. 2, a primary fuel supply means 62 formed as a low pressure supply system. Preferably, the primary fuel feeder 62 is a low-pressure injector having a single-fluid nozzle, but may be an evaporation-type fuel feeder having a porous vaporization unit such as a non-woven evaporation unit. The low-pressure supply system works with a feed pressure of up to 10 bar. Further, the reformer 12 of the second embodiment has a secondary fuel supply device 64, which is designed as a high-pressure feed system. The high-pressure feed system is an injection system which is operated at 900 to 1100 bar, and can preferably with approx.

1000 bar are operated. This pressure can be realized for example with a common rail system. Alternatively, the high-pressure feed system can be operated with a feed pressure of 50 to 100 bar, which can be achieved for example by means of a pressure surge injection system.

In a modification of the second exemplary embodiment, the primary fuel supply device 62 is designed as an injection nozzle and the secondary fuel supply device 64 is designed as an evaporation-type fuel supply device which has a porous evaporation unit, for example a fleece evaporation unit. _ _{± 2} _

In a second modification of the second embodiment, the primary fuel supply 62 and the secondary fuel supply 64 are formed or operated such that the fuel supplied from the primary fuel supply 62 has a different temperature from that supplied to the corresponding zone of the reformer 12 the secondary fuel supply 64 supplied fuel. Alternatively, this different feed temperature of the fuel can also be achieved by means of a heating or cooling device in the first and / or second fuel strands 14, 18. This temperature difference may also cause the fuel to be supplied to the primary fuel supply 62 in a different state than to the secondary fuel supply 64.

It is explicitly pointed out that although the individual embodiments and their modifications have been described separately with reference to assigned figures, any combination of the individual embodiments and modifications is within the scope of the invention. For example, a combination of the first and second embodiments is quite possible, be supplied to the different types of fuel to a fuel reformer, which has a high and Niederdruckbrennstoffzuführeinrichtung.

Although this is not explicitly illustrated in the figures described, suitable delivery devices, such as, for example, pumps or blowers and / or control valves for flow regulation, may be provided in the fuel strands 14, 18 and 38, in the oxidant strands 22 and 40 and in the cathode air strands 28. The features of the invention disclosed in the foregoing description, in the drawings and in the claims may be essential to the realization of the invention both individually and in any combination.

List of reference numbers:

10 fuel cell system

12 reformer 14 first fuel strands

16 first fuel tank

18 second fuel strands

20 second fuel tank

22 first oxidant strand 24 Reformatstrang

26 fuel cell stack

28 cathode supply air line 30 electrical connections 32 anode exhaust line 34 mixing unit

36 afterburner

38 third fuel strand

40 second oxidant strand

42 mixing unit 44 cathode exhaust line

46 heat exchanger 48 oxidation zone

50 primary fuel feeder

52 Oxidant agent supply device 54 mixing zone

56 secondary fuel supply

58 reforming zone

60 fuel tank

62 primary fuel supply 64 senkundäre fuel supply

Claims

- -CLAIMS

A reformer (12) for a fuel cell system (10), comprising:

an oxidation zone (48) to which stored fuel can be fed by means of a primary fuel feed device (50; 62) for reaction with oxidant; and

a mixing zone (54) disposed downstream of the oxidation zone (48), which stored fuel is deliverable by means of a secondary fuel supply means (56; 64) for mixing with materials exiting the oxidation zone (48),

characterized in that the primary fuel supply means (50; 62) and the secondary fuel supply means (56; 64) are adapted to supply fuel such that the fuel supplied from the primary fuel supply means (50; 62) is different from that from the secondary fuel supply means (50; 56, 64) differs in terms of fuel grade and / or aggregate state and / or feed pressure and / or feed temperature.

2. reformer (12) according to claim 1, characterized in that the primary fuel supply means (62) has a low pressure supply means with a supply pressure of at most 10 bar and the secondary fuel supply (64) is a high-pressure feeder with a feed pressure of more than 50 bar.

3. reformer (12) according to claim 2, marked thereby, that the secondary Brennstoffzuführeinrichtung (64) is a high-pressure feeder with a feed pressure of 50 to 100 bar.

4. reformer (12) according to claim 2, marked thereby, that the secondary fuel supply means (64) is a high-pressure feeder with a supply pressure of 900 to 1100 bar.

5. A reformer (12) according to any one of the preceding claims, characterized in that the primary fuel supply means (50) is adapted to be connected to a first fuel tank (16) and the secondary fuel supply means (56) is adapted to to be connected to a separate second fuel tank (20).

6. Fuel cell system (10) with a reformer (12) according to one of the preceding claims.

7. Motor vehicle with a fuel cell system (10) according to claim 6.

8. Motor vehicle according to claim 7, characterized in that two fuel tanks (16, 20) are provided, wherein one of the fuel tanks (16) with the primary

Fuel supply means (50) of the reformer (12) is connected and the second fuel tank (20) with the secondary fuel supply means (56) is connected.

9. A method of operating a reformer (12) of a fuel cell system (10), comprising the steps of:

Supplying fuel in a fuel tank (16, 60) to an oxidation zone (48) in which the fuel is convertible with oxidant; and

Supplying fuel in a fuel tank (20; 60) to a mixing zone (54) located downstream of the oxidation zone (48), in which the fuel is miscible with materials exiting the oxidation zone (48),

characterized in that that of the oxidation zone

(48) supplied fuel from the mixing zone (54) supplied fuel with respect to fuel grade and / or state of aggregation and / or supply pressure and / or supply temperature differs.

10. The method according to claim 9, characterized in that the oxidation zone (48) supplied fuel with a feed pressure of at most 10 bar and the mixing zone (54) supplied fuel with a feed pressure of more than 50 bar is supplied.

11. The method according to claim 10, characterized in that the mixing zone (54) supplied fuel is supplied at a feed pressure of 50 to 100 bar.

12. The method according to claim 10, characterized in that the mixing zone (54) supplied fuel is supplied at a feed pressure of 900 to 1100 bar.

13. The method according to any one of claims 9 to 12, characterized in that the fuel supplied to the oxidation zone (48) from a first fuel tank (16) and the mixing zone (54) supplied fuel from a separate second fuel tank (20) is supplied.