AT522939B1 - Burner for a fuel cell system - Google Patents

Abstract

The invention relates to a burner (1), a fuel cell system (100), in particular an SOFC system, wherein the burner (1) is designed and arranged as a starting burner and / or afterburner and comprises two reaction chambers (2, 3) arranged one after the other, wherein in Direction of flow a second reaction chamber (3) indirectly follows a first reaction chamber (2), the reaction chambers (2, 3) each having a catalytic material, an evaporation device (4) being provided, the evaporation device (4) between the reaction chambers ( 2, 3), a further evaporator (6) being provided for evaporating fuel, the further evaporator (6) being arranged upstream of the evaporation device (4). The invention also relates to a fuel cell system (100) with such a burner (1). The invention also relates to a method for operating a fuel cell system (100) with a burner (1).

Description

description

BURNER FOR A FUEL CELL SYSTEM

The invention relates to a burner for a fuel cell system, in particular an SOFC system, wherein the burner is designed and arranged as a starting burner and / or afterburner and comprises two reaction chambers arranged one after the other, a second reaction chamber indirectly following a first reaction chamber in the flow direction , the reaction chambers each having a catalytic material, an evaporation device being provided.

The invention further relates to a use of such a burner. The invention also relates to a fuel cell system with such a burner.

The invention also relates to a method for operating a fuel cell system.

Burners for fuel cell systems are known from the prior art. In the case of SOFC systems in particular, which are operated with liquid fuel such as diesel or ethanol or an ethanol-water mixture, it may be necessary to vaporize and reform the liquid fuel in a first step. Particularly when using water-containing ethanol, it is difficult or even impossible to burn the fuel in a flame burner, which is used, for example, in fuel cell systems that run on diesel, due to the high water content (about 55%).

It is also necessary to heat the fuel cell system to an operating temperature during a cold start, for which a so-called starter burner is usually provided. In addition, an afterburner is usually also necessary in order to completely burn off exhaust gas from an anode section. Consequently, a starting burner and an afterburner are usually provided in known fuel cell systems.

The starting burner is usually understood to mean a starting burner for heating an afterburner of the fuel cell system, which in turn is provided for heating a reformer of the fuel cell system. In the event of a cold start of the fuel cell system, when the afterburner is still cold and is therefore not suitable for heating a reformer of the fuel cell system, the afterburner can be preheated by the starting burner. As soon as the afterburner is at operating temperature due to the operation of the fuel cell system, the starting burner can be deactivated.

From DE 102 37 744 A1, for example, a fuel cell system with a starting burner, which is installed in a burner housing, emerges.

Furthermore, DE 10 2006 048 984 A1 discloses the use of a burner device in a fuel cell system. The burner device can be operated as an afterburner and starting burner.

However, this publication does not reveal how, in particular, a fuel cell system operated with a liquid fuel can be efficiently brought to operating temperature.

Further burners for a fuel cell system with two reaction chambers are known, for example, from FR 2899022 A1, EP 1465274 A2 and WO 2019075502 A1.

The object of the invention is to increase the efficiency of a burner of the type mentioned at the outset, by means of which a fuel cell system can be brought to operating temperature quickly and effectively.

It is also an aim to specify a fuel cell system with such a burner. Furthermore, it is an aim to provide an improved method for operating a fuel cell

systems.

This object is achieved according to the invention in that in a burner of the type mentioned, the evaporation device is arranged between the reaction chambers, a further evaporator being provided for evaporating fuel, the further evaporator being arranged upstream of the evaporation device.

An advantage achieved in this way is seen in the fact that the design of the burner according to the invention means that heat transfer works particularly effectively. A burner designed in this way can be designed and arranged both as a starting burner and as an afterburner. That is, a single component functions simultaneously as a starting burner and as an afterburner, depending on an operating state of a fuel cell system in which the burner is arranged. The burner is designed as a multi-stage burner, the first reaction chamber forming a first stage, the second reaction chamber forming a second stage and the evaporation device forming a further stage. In the burner according to the invention, the fuel can on the one hand be vaporized and at least partially reformed and on the other hand it can also be completely burned and heated to a necessary or predefined temperature. A process gas which flows out of the burner has a sufficiently high temperature due to the multi-stage design of the burner to heat several elements of a fuel cell system. Furthermore, fuel cell exhaust gas, which exits from an anode section and a cathode section of the fuel cell stack, can be completely afterburned in the burner, a separate afterburner thus being unnecessary, since the burner can be used as a starting burner and afterburner in a single fuel cell system. A mixture of air and a fuel-water mixture or fuel cell exhaust gas flows through the two reaction chambers one after the other; the second reaction chamber is thus arranged downstream of the first reaction chamber, the evaporation device being arranged therebetween. So they are arranged one after the other in the direction of flow.

According to the invention, an evaporation device is provided, this being structurally arranged between the two reaction chambers. That is to say, this is arranged in particular immediately after a first reaction chamber and in particular immediately in front of a second reaction chamber. The warm side of the evaporation device is arranged between the reaction chambers in the direction of flow. The evaporation device is designed and arranged to heat up liquid fuel and to put it in a gaseous state. For example, fuel enters the cold side of the evaporation chamber at around 25 ° C and exits it in gaseous form at around 800 ° C. Downstream of the cold side of the evaporation chamber, the now gaseous fuel is directed into the first reaction chamber. In addition, an oxygen-containing, gaseous fluid, in particular air, is fed into the first reaction chamber, the gaseous fuel and the air being mixed with one another, in particular immediately upstream of the first reaction chamber.

According to a first aspect of the present invention, a burner for a fuel cell system, in particular for an SOFC system (SOFC stands for "solid oxide fuel cell", or solid oxide fuel cell) is provided. Such a fuel cell system can be operated with liquid fuel, for example.

In the context of the invention, air is to be understood as an oxygen-containing fluid which is in particular gaseous. In particular, air is understood to mean ambient air. The fuel is a fuel, which is preferably a liquid fuel-water mixture, in particular an ethanol-water mixture.

The burner is designed in particular to burn liquid fuel catalytically, for which purpose both reaction chambers each comprise a catalytic material. Due to the pre-evaporation and partial pre-reforming of the fuel, the concept of the burner in particular enables an ethanol-water mixture to be used as fuel, which is known to be difficult to evaporate and subsequently burn due to its high water content. This makes it possible to use the highly water-containing fuel,

cher for steam reforming without necessary recirculation on the anode side is also intended to be used for the starting process. If the burner according to the invention is arranged in a fuel cell system, this can, however, easily be operated with a liquid fuel-water mixture such as with an ethanol-water mixture.

It is advantageous if the evaporation device comprises two evaporation chambers. A second evaporation chamber is preferably arranged downstream of a first evaporation chamber. Both evaporation chambers are advantageously arranged and designed to absorb heat, the first evaporation chamber absorbing heat from the first reaction chamber and the second evaporation chamber absorbing heat from the first evaporation chamber. This takes place over or on a warm side of the respective evaporation chambers. It is advantageous if a separate control device for a separate fuel supply is provided for each evaporation chamber. The control device is designed as an injector or as a valve and is preferably provided upstream of a further evaporator which is arranged upstream of the evaporation device. Via the first evaporation chamber, fuel can be evaporated via a cold side (by means of heat from the first reaction chamber) and an at least partially burned fuel-air mixture can be conducted to the second evaporation chamber via a warm side. Accordingly, fuel, which is fed into the cold side of the second evaporation chamber via a second control device, which is again designed as an injector and / or valve, can be evaporated via the second evaporation chamber and then fed into the second reaction chamber. Likewise, the at least partially burned fuel-air mixture can be passed on into the second reaction chamber for complete combustion. The first evaporation chamber is in particular arranged downstream of the chamber outlet of the first reaction chamber and the second evaporation chamber is arranged upstream of the chamber inlet of the second reaction chamber. In particular, the two evaporation chambers directly adjoin one another.

It is advantageous if a mixing area is provided upstream of the first reaction chamber, the mixing area being arranged in particular at a chamber inlet of the first reaction chamber. The mixing region is consequently arranged in particular directly upstream of the first reaction chamber and is preferably designed to mix air and gaseous fuel when the fuel cell system is started. A resulting fuel-air mixture is then passed into the first reaction chamber and is at least partially burned there. During ongoing or nominal operation, the mixing chamber generally has no special function, because in this operating state the burner works as an afterburner and fuel cell stack exhaust gas is burned in it. In principle, it is advantageous if anode exhaust gas is mixed with cathode exhaust gas (air) upstream of the mixing chamber for this purpose. However, it can also be provided that this takes place in the mixing chamber. It is important that a fuel-air mixture already enters the first reaction chamber. The mixing area can also be designed as part of the first reaction chamber or connected to it.

[0023] It can be advantageous if the reaction chambers and the evaporation device are each designed to be rotationally symmetrical at least in sections, these each comprising at least two, in particular, cylindrical layers. Particularly preferably, the reaction chambers and the evaporation chambers are each designed at least partially as a hollow cylinder. The cylindrical layers are in particular plugged into one another coaxially or arranged in relation to one another. As a result, chambers can form between the cylindrical layers.

A further evaporator is provided for a starting operation and / or heating operation of the burner, the further evaporator being arranged upstream of the evaporation device. This is necessary for a cold start of the fuel cell system, in particular the burner, since the evaporation device is not yet warm, so that no heat is available in it for evaporating the fuel. The further evaporator usually includes a heating device, so that this is a necessary for the evaporation of fuel

agile temperature reached. During a cold start, the evaporation device therefore initially has no function. It is also advantageous if the further evaporator has a reformer unit so that the fuel not only evaporates when it is heated, but is also at least partially reformed. As a result, the temperature of the fuel when it exits the further evaporator is around 600 ° C.

It is advantageous here if the further evaporator comprises an electrical heating device. Fuel is thus evaporated by the electrical heating device, whereby this can be about 600 ° C. downstream of the further evaporator. As soon as the burner has the necessary operating temperature so that sufficient heat is generated in the first reaction chamber for the first evaporation chamber, the electrical heating device can be switched off. This takes place in particular when an ignition takes place in the first reaction chamber. Now the other evaporator no longer has any function, since the fuel is evaporated in the evaporation device. The electric heating device means that the burner is in a starting phase d. H. Electrically preheatable when starting the burner from cold. In particular, the electrical heating device is designed to heat the fuel; the electrical heating device is particularly preferably designed exclusively to heat, vaporize and / or reform the fuel during a warm-up phase of the burner functioning as a starter burner. The fuel, which can be present as fuel or as a fuel-water mixture, is consequently not only preheatable, but also vaporizable and, to a certain predetermined degree, prereformable. As a result, the burner can be operated particularly effectively when used as a starting burner. In a heating operation, the electrical heating device can be in operation for a period of approximately 2 minutes to 10 minutes, for example. After the electrical heating device has been switched off, fuel continues to be directed via the first injector in the direction of the first evaporation chamber until a nominal operating point of the fuel cell system is reached. The fuel is then evaporated in the first evaporation chamber by the heat which is generated during the exothermic reaction in the first reaction chamber. When the burner is used as an afterburner, the electrical heating device is generally not used. The electrical support for evaporation and reforming can in principle be carried out in an external component, but integration of this function is desirable for reasons of space.

It is advantageous if a first fuel supply line is provided, wherein fuel can be conducted via the further evaporator and the evaporation device, in particular a first evaporation chamber, into the mixing area and then into the first reaction chamber via the first fuel supply line. The fuel supply line is designed to supply a first operating fluid in the form of fuel to the burner or the first reaction chamber. In particular, a first injector and / or a first valve is arranged upstream of the first fuel supply line. Fuel can be fed into the first fuel supply line via the injector, this taking place in particular during a starting operation, that is to say when the burner is used as a starting burner. As soon as the burner and the fuel cell system have reached a nominal operating point, the first control device is brought into a closed state so that no more fuel is supplied; the burner is now used as an afterburner.

At the same time, the evaporation chambers no longer have any function during nominal operation. The first fuel supply line extends in particular from a fuel source via the further evaporator, the evaporation device to the mixing area and the first reaction chamber and / or connects these elements to one another.

It is further advantageous if an air supply line is provided, with air being able to be conducted into the mixing area and then into the first reaction chamber via the air supply line. The mixing area is designed and arranged for mixing the fuel and the air. When the burner is used as a starting burner, air and fuel are therefore brought together in the mixing chamber. When the burner is used as an afterburner, in particular in nominal operation, preferably only fuel cell stack exhaust gas, which in particular already comprises cathode and anode exhaust gas, is fed into the burner. It can

however, it can also be provided that air is additionally fed into the first reaction chamber via the air supply line and / or fuel via the first fuel supply line. The air supply line therefore extends in particular from an air source via the mixing area into the first reaction chamber.

It can also be favorable if a second fuel supply line is provided, wherein fuel can be conducted via the second fuel supply line via the second evaporation chamber into the second reaction chamber. Upstream of the second fuel supply line, an injector is again advantageously arranged, which is open and can be closed for conveying fuel. During a start-up phase of the burner, fuel can be fed directly from the second injector or from the second valve into the second evaporation chamber via the second fuel supply line, which fuel can be evaporated with the heat of the at least partially burned fuel-air mixture exiting the first evaporation chamber. The second reaction chamber, which is brought to operating temperature by the evaporated fuel when the burner is started, is arranged downstream of the second evaporation chamber. In nominal operation, the second control device is generally also switched off and as a result no more fuel is passed through the second fuel supply line.

It is advantageous if a system exhaust line is provided, with system exhaust gas being able to be conducted via the mixing area into the burner via the system exhaust line. System exhaust gas is fuel cell stack exhaust gas, to which anode exhaust gas and cathode exhaust gas are mixed in particular immediately downstream of the fuel cell stack. In particular, this line is used exclusively in nominal operation and connects the at least one fuel cell stack to the burner. If the burner assumes the function of an afterburner, anode exhaust gas or fuel cell exhaust gas (anode exhaust gas and cathode exhaust gas) flows in the system exhaust line and is fed to the burner in order to burn it completely. Since the cathode exhaust gas is in particular exclusively air, the anode exhaust gas is burned in the burner with the cathode exhaust gas. If the temperature is too high when the burner is operating as an afterburner, it can be advantageous to additionally supply air to the burner via the air supply line. As a rule, nothing flows in the first and second fuel supply lines; these are not in operation. In the context of the invention, system exhaust gas stack is understood to mean exhaust gas.

A burner according to the invention is advantageously used as a starting burner and afterburner in a fuel cell system which is operated with liquid fuel.

According to a further aspect of the present invention, a fuel cell system is provided with a burner as shown in detail above. The fuel cell system also has a fuel cell stack with an anode section and a cathode section, a reformer and heat exchanger, the burner being arranged and configured for heating the reformer and at least one heat exchanger, which is responsible for heating air to be fed to the cathode section. A fuel cell system according to the invention thus has the same advantages as have been described in detail with reference to the burner according to the invention.

The fuel cell system is preferably an SOFC system. The reformer is preferably designed for reforming a fuel mixture, for example ethanol and water, into another fuel mixture, in this case hydrogen and carbon dioxide. The reformed hydrogen can be used in a fuel cell stack to generate electricity. The burner is designed to heat the reformer by means of fuel cell exhaust gas from the fuel cell stack.

In an advantageous development of the present invention, it is possible that a further heat exchanger is provided, wherein process gas that exits the burner flows over a warm side of the heat exchanger and air that flows over a cold side of the heat exchanger to a cathode section of the Fuel cell stack flows, heated. The fuel cell system according to the invention is used in particular in a motor vehicle.

The further aim is achieved if a method of the type mentioned at the outset comprises the following steps:

[0036] An electrical heating device is put into operation and a fuel is introduced into a first fuel supply line via a first control device, the fuel being passed via the first fuel supply line into a further evaporator in order to at least evaporate the fuel;

[0037] Introducing air through an air supply line into a mixing region upstream of a first reaction chamber;

[0038] Directing the fuel via the first fuel supply line from the further evaporator through a first evaporation chamber to the mixing area upstream of the first reaction chamber;

- Mixing the fuel with the air in the mixing area and introducing this fuel-air mixture into the first reaction chamber;

- Catalytic combustion of the fuel-air mixture; - Switching off the electrical heating device.

An advantage achieved in this way is to be seen in particular in the fact that a fuel cell system can be heated up efficiently and in a short time through the steps of the method according to the invention, the burner itself also being heated up efficiently and quickly and a cold start time being reduced. As soon as the fuel-air mixture is burned, the electrical heating device is switched off, since the combustion generates heat which warms up a first evaporation chamber. The fuel is now evaporated through the first evaporation chamber until the nominal operating point is reached. As soon as the electrical heating device is switched off, a self-sustaining operating point is reached. By carrying out all the method steps according to the invention, the fuel cell system is thus heated up, so that a nominal operating point is reached. Not only are the reaction chambers of the burner warmed up, but in particular the evaporation device, which is arranged between two reaction chambers, is also warmed up.

In particular, the fuel is not only completely evaporated in the further evaporator, but preferably also superheated and also at least partially pre-reformed. Thus, the electrical heating device can initially be activated for heating or preheating the fuel until a defined operating temperature is reached in the burner. As soon as the defined operating temperature is reached, the electrical heating device can be deactivated. The remaining procedural steps are then repeated. The other advantages and functions associated with the functioning of the burner as a starting burner are the same as have been described in detail above with reference to the burner according to the invention and the fuel cell system according to the invention.

It is also advantageous if the at least partially burned fuel-air mixture is passed from the first evaporation chamber into a second evaporation chamber, after which it is passed into a second reaction chamber. The fuel-air mixture is completely catalytically burned in the second reaction chamber and has a temperature in the range between 800 ° C. and 900 ° C. at the exit of the burner, which is also the exit of the second reaction chamber, and is now a process gas.

In order to improve and / or accelerate the catalytic reaction in the second reaction chamber, fuel is expediently passed via a second control device via a second fuel supply line into a cold side of the second evaporation chamber, evaporated and passed downstream thereof into the second reaction chamber. This fuel is evaporated in the second evaporation chamber, for which purpose heat from the fuel-air mixture which emerges from the first evaporation chamber is used. The vaporized fuel is then passed into the second reaction chamber, where it is completely mixed with the fuel-air mixture which has been at least partially reformed in the first reaction chamber

catalytically burned. The fuel-air mixture has a temperature of approximately 650 ° C. or less downstream of the second evaporation chamber, since this has given off heat to both evaporation chambers in particular to evaporate fuel.

It is advantageous if the fuel-air mixture, which has been completely reformed in the second reaction chamber, is used downstream of the burner at least for heating a reformer and a heat exchanger. A process gas emerging from the burner has a temperature between 800 ° C. and 900 ° C., in particular approximately 950 ° C., and can additionally or alternatively also be used to heat an evaporator. If all elements of a fuel cell system are at operating temperature, the now cooled process gas is released into the environment.

The first and / or second regulating device can advantageously be designed as an injector within the scope of the invention. Alternatively, the first and / or second regulating device can also be designed as at least one, in particular controllable, valve. However, it can also be provided that the first and / or second control device comprises an injector and at least one valve.

It is advantageous if the control devices are switched off so that a fuel supply via the fuel supply lines is stopped as soon as a self-sustaining operating point of the fuel cell system is reached. The burner is then used as an afterburner, fuel cell stack exhaust gas, which in particular comprises anode exhaust gas and cathode exhaust gas, being fed to this. The fuel cell stack exhaust gas is fed to the first reaction chamber downstream of the fuel cell stack, where it is at least partially burned catalytically and passed through the two evaporation chambers into the second reaction chamber in order to be completely burned. Since no more fuel is fed to the evaporation chambers, these are also out of operation. Although it can be beneficial when the burner is functioning as an afterburner if air is no longer supplied to the burner, it can be advantageous if air is supplied to the burner at least temporarily via the air supply line.

Further advantages, features and effects result from the exemplary embodiments presented below. The drawings to which reference is made show:

1 shows a schematic representation of a burner according to the invention; FIG. 2 shows a section through a burner according to the invention;

Fig. 3 is a block diagram showing a fuel cell system according to an embodiment of the present invention.

1 and 2 show a burner 1 according to the invention or sections thereof for a fuel cell system 100. This comprises two reaction chambers 2, 3 which are arranged indirectly one behind the other in the direction of flow. Each reaction chamber 2, 3 each has a chamber inlet and a chamber outlet. The burner 1 also has a first fuel supply line 7 and an air supply line 8, the first fuel supply line 7 being designed to guide a fuel and the air supply line 8 to be designed to guide air. In the context of the invention, an ethanol / water mixture is preferably used as fuel. An evaporation device 4 having two evaporation chambers 4a, 4b is provided between the two reaction chambers 2, 3. A further evaporator 6 is arranged upstream of the evaporation device 4 and comprises an electrical heating device (not shown). The further evaporator 6 is designed such that the same fuel is evaporated in a first part in the flow direction and the fuel is at least partially reformed in a second part of the evaporator in the flow direction. As a result, the further evaporator 6 is also designed as a reformer, this comprises an evaporator unit 6a and a reformer unit 6b, the reformer unit 6b being arranged downstream of the evaporator unit 6a and taking up about twice as much volume as the evaporator unit 6a. The further evaporator 6 further comprises an electrical heating device. A fuel feed line 7 is provided for introducing and forwarding fuel, in FIG

which fuel can be conducted into the further evaporator 6 via a first regulating device 11 designed as a first injector. The fuel supply line 7 leads further into the first evaporation chamber 4a and then further into the mixing area 5 and into the first reaction chamber 2. The evaporated and at least partially reformed fuel has a temperature of about 600 ° C. downstream of the further evaporator 6 and upstream of the first evaporation chamber 4a on. This is passed through the first evaporation chamber 4a, which has no further function during a start phase. In the mixing area 5, the vaporized and partially reformed fuel is mixed with air, which is passed into the mixing area 5 via an air supply line 8. The resulting fuel-air mixture is passed through the first reaction chamber 2, through the first evaporation chamber 4a, through the second evaporation chamber 4b and through the second reaction chamber 3 in order to bring these components to operating temperature. The two reaction chambers 4a, 4b are heated by the hot fuel-air mixture; the catalytic material of the same is brought to operating temperature and ignited. As soon as this is done, the heating device is switched off. This usually takes about 2 minutes to 10 minutes. Now fuel is supplied via the first injector until a nominal operating point is reached. The liquid fuel is directed to the first evaporation chamber 4a, where it is evaporated (via the heat of the fuel-air mixture, which is passed over a hot side of the same). The now gaseous fuel is mixed with air in the mixing area and fed into the first reaction chamber 2, in which the fuel-air mixture is at least partially burned catalytically. Downstream of the first reaction chamber is the first evaporation chamber 4a, in which the at least partially burned fuel-air mixture is used for evaporation or heat exchange with the fuel which flows over a cold side of the first evaporation chamber 4a. As long as the nominal operating point has not yet been reached, fuel is fed via a second fuel supply line 9 into the second evaporation chamber 4b via a second control device 12 designed as a second injector. This therefore flows over a cold side of the second evaporation chamber 4b. The at least partially burned fuel-air mixture is passed over the warm side of the second evaporation chamber, the heat of the fuel-air mixture (approx. 650 ° C.) being used to evaporate the fuel in the second fuel supply line 9. Both the fuel-air mixture and the fuel that has now evaporated are fed into the second reaction chamber 3, where complete catalytic combustion takes place. The gas emerging from the second reaction chamber 3 and thus from the burner 1 now has a temperature in the range from 800 ° C. to 900 ° C. and can be used to heat the other components of the fuel cell system 100. As soon as all the components of the fuel cell system 100 are brought to operating temperature, a nominal operating point is reached and the two control devices 11, 12 designed as injectors are switched off.

In nominal operation, the burner 1 is used as an afterburner, exhaust gas being fed to it via a system exhaust line 10, so that it is completely catalytically burned in the burner 1.

3 shows a block diagram of a fuel cell system 100 with the burner 1, not all details of the burner 1 being shown. The fuel cell system 1 further comprises two fuel cell stacks 200, each with an anode section 300 and a cathode section 400. In addition, a reformer 500 and a heat exchanger are provided. In addition, the fuel cell system 100 comprises an evaporator 800 for evaporating fuel, which is directed in the direction of the reformer 500, and a superheater 700 for superheating the fuel evaporated by the evaporator 800. The stack exhaust gas, which provides the heat required for the above-mentioned processes, is passed over a warm side of the reformer 500, the superheater 700 and the evaporator 800. The fuel cell system 100 is operated with a liquid fuel-water mixture, which is usually referred to as fuel in the context of the invention. This is fed from a fuel source 13 via an anode feed line via the evaporator 800 (there the fuel-water mixture becomes gaseous), the superheater 700 and the reformer 500 (there the gaseous fuel-water mixture is reformed) to the anode section 300.

leads. Via a cathode supply line 10, air is supplied to the cathode section 400 by a fan 14 via a heat exchanger 600. These steps are carried out as soon as the fuel cell system 100 is in operation, that is to say after a heating-up operation.

To heat the fuel cell system 100, the burner 1 according to the invention is used as a starting burner, as described above.

When operating the fuel cell system 100, the burner 1 is used as an afterburner. The anode off-gas is mixed with the cathode off-gas downstream of the fuel cell stacks 200. This stack exhaust gas is fed in via the burner 1 and there, in particular, is burned in two stages.

The burner 1 according to the invention can be used in a fuel cell system 100 both as a starting burner and as an afterburner. When the fuel cell system 100 is heated up, it is used as a starting burner and when the fuel cell system 100 is operated as an afterburner. In a first step, the burner 1 is used as a starting burner during a cold start (electrical heating device is in operation), during a warm-up phase (electrical heating device is switched off, but injectors are open) and in nominal operation (no more fuel is supplied via the valves). used as an afterburner.

Claims (14)

Claims 1. Burner (1) for a fuel cell system (100), in particular an SOFC system, the burner (1) being designed and arranged as a starting burner and / or afterburner and comprising two reaction chambers (2, 3) arranged one after the other, with in the direction of flow a second reaction chamber (3) indirectly follows a first reaction chamber (2), the reaction chambers (2, 3) each having a catalytic material, an evaporation device (4) being provided, characterized in that the evaporation device (4) is between the Reaction chambers (2, 3) is arranged, a further evaporator (6) being provided for evaporating fuel, the further evaporator (6) being arranged upstream of the evaporation device (4). 2. Burner (1) according to claim 1, characterized in that the evaporation device (4) comprises two evaporation chambers (4a, 4b). 3. Burner (1) according to claim 1 or 2, characterized in that a mixing area (5) is provided upstream of the first reaction chamber (2), the mixing area (5) being arranged in particular at a chamber inlet of the first reaction chamber (2). 4. Burner (1) according to one of claims 1 to 3, characterized in that the further evaporator comprises an electrical heating device. 5. Burner (1) according to one of claims 1 to 4, characterized in that a first fuel supply line (7) is provided, wherein via the first fuel supply line (7) fuel via the further evaporator (6) and the evaporation device (4), in particular a first evaporation chamber (4a) can be directed into the mixing region (5) and then into the first reaction chamber (2). 6. Burner (1) according to one of claims 3 to 5, characterized in that an air supply line (8) is provided, air being conducted into the mixing region (5) and then into the first reaction chamber (2) via the air supply line (8) is. 7. Burner (1) according to one of claims 2 to 6, characterized in that a second fuel supply line (9) is provided, wherein via the second fuel supply line (9) fuel via the second evaporation chamber (4b) into the second reaction chamber (3) is controllable. 8. Burner (1) according to one of claims 3 to 7, characterized in that a system exhaust line (10) is provided, wherein the system exhaust line (10) via the mixing area (5) in the burner (1) can be conducted. 9. Fuel cell system (100), in particular SOFC system, with a burner according to one of claims 1 to 8, characterized in that the fuel cell system further comprises at least one fuel cell stack (200) with an anode section (300) and a cathode section (400), a Has reformer (500) and heat exchanger (600). 10. A method for operating a fuel cell system (100) with a burner (1) according to one of claims 1 to 8, in particular a fuel cell system (100) according to claim 9, the method comprising the following steps: - An electrical heating device is put into operation and a fuel is introduced into a first fuel supply line (7) via a first control device, the fuel being passed via the first fuel supply line (7) into a further evaporator (6) in order to at least evaporate the fuel; - Introducing air through an air supply line (8) into a mixing region (5) upstream of a first reaction chamber (2); - Directing the fuel via the first fuel supply line (7) from the further evaporator (6) through a first evaporation chamber (4a) to the mixing region (5) upstream of the first reaction chamber (2); - Mixing the fuel with the air in the mixing area (5) and introducing this fuel-air mixture into the first reaction chamber (2); - Catalytic combustion of the fuel-air mixture; - Switching off the electrical heating device. 11. The method according to claim 10, characterized in that the at least partially burned fuel-air mixture from the first evaporation chamber (4a) is passed into a second evaporation chamber (4b), after which it is passed into a second reaction chamber (3). 12. The method according to claim 11, characterized in that fuel is passed via a second fuel supply line (9) into a cold side of the second evaporation chamber (4b) via a second control device (12), evaporates and directed downstream thereof into the second reaction chamber (3) will. 13. The method according to claim 12, characterized in that the fuel-air mixture completely burned in the second reaction chamber (3) is used downstream of the burner (1) at least to heat a reformer (500) and a heat exchanger (600). 14. The method according to any one of claims 10 to 13, characterized in that the control devices (11, 12) are switched off so that a fuel supply via the fuel supply lines (7, 9) is stopped as soon as a self-sustaining operating point of the fuel cell system (100) is reached . In addition 3 sheets of drawings