AT519833B1 - Fuel cell system with process liquid source - Google Patents

Abstract

The invention relates to a fuel cell system (100a; 100b; 100c; 100d), comprising a fuel cell stack (1) with an anode section (2) and a cathode section (3), a reformer (4) for pre-reforming a fuel supplied to the fuel cell stack, at least one Evaporators (5) for evaporating a fuel and / or a process liquid for use in the reformer (4), a fuel source (6) for providing fuel for a fuel mixture in the reformer (4), and a process liquid source (7, 8) for providing Process liquid for the fuel mixture in the reformer (4), wherein a fuel pump (9) for pumping the fuel from the fuel source (6) to the evaporator (5), and downstream of the fuel source (6) and upstream of the at least one evaporator (5) Process liquid source (7, 8) and upstream of the at least one evaporator (5) a process liquid pump (1 0) for pumping the process liquid from the process liquid source (7, 8) to the evaporator (5), wherein a fuel injector (15) for injecting the fuel into the evaporator (5) is arranged downstream of the fuel pump (9) and downstream of the process liquid pump (10) a process liquid injector (16) for injecting the process liquid into the evaporator (5) is arranged. The invention further relates to a motor vehicle (1000) with a fuel cell system (100a; 100b; 100c; 100d) according to the invention.

Description

The present invention relates to a fuel cell system, in particular a SOFC system, comprising a fuel cell stack with an anode section and a cathode section, a reformer for pre-reforming a fuel supplied to the fuel cell stack, at least one evaporator for evaporating the fuel and / or a process liquid for use in the reformer , a fuel source for providing fuel for a fuel mixture in the reformer, and a process fluid source for providing process fluid for the fuel mixture in the reformer. The invention further relates to a motor vehicle with such a fuel cell system.

SOFC systems are well suited due to their high efficiency and the possibility of using many different fuels such as diesel or ethanol. In order to use such fuels in SOFC systems, these fuels are pre-reformed in order to reduce the reforming requirement on an anode section of a fuel cell stack of the SOFC system. Pre-reformed fuel and a process liquid, such as water in particular, which is used for reforming in the SOFC system, can be fed to a reformer or an evaporator upstream of the reformer in various ways. One possibility is to lead anode exhaust gas with a high water content via a recirculation system to the evaporator upstream of the reformer. However, a fluid line system required for this is of relatively complex construction and is accordingly difficult to implement. Another possibility is to provide water and fuel in a tank as a finished fluid mixture. In this case, no recirculation blower is required, which can reduce costs and increase the efficiency of the overall system. However, this possibility of providing water and fuel is only conditionally suitable for mobile use. In (hybrid) electric vehicles, the amount of water and fuel required for a SOFC system is so large that a suitable tank filling would lead to an unsatisfactorily high overall weight of the electric vehicle. Furthermore, the finished fuel mixture cannot react to changing environmental conditions.

Such SOFC systems are known for example from EP 2963720 A1, WO 2007015562 A1 and US 2002062943 A1.

The object of the present invention is to at least partially remedy the disadvantages described above. In particular, it is an object of the present invention to provide a fuel cell system and a motor vehicle, by means of which a process liquid such as water and fuel can be provided for one or more evaporators of a reformer in a simple, inexpensive and space-saving manner.

The above object is solved by the claims. In particular, the above object is achieved by the fuel cell system according to claim 1 and the motor vehicle according to claim 9. Further advantages of the invention result from the subclaims, the description and the drawings. Features and details that are described in connection with the fuel cell system apply, of course, also in connection with the motor vehicle according to the invention and vice versa, so that with respect to the disclosure of the individual aspects of the invention, reference can always be made to one another.

[0006] According to a first aspect of the present invention, a fuel cell system with a fuel cell stack is provided. The fuel cell stack has an anode section and a cathode section. The fuel cell system also has a reformer for pre-reforming the fuel supplied to the fuel cell stack, at least one evaporator for evaporating the fuel and / or a process liquid for use in the reformer, a fuel source for providing fuel for a fuel mixture in the reformer, and a process liquid source for providing

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AT 519 833 B1 2020-02-15 Austrian patent office for process liquid for the fuel mixture in the reformer. A fuel pump for pumping the fuel from the fuel source to the evaporator is arranged downstream of the fuel source and upstream of the at least one evaporator, and a process liquid pump for pumping the process liquid from the process liquid source to the evaporator is arranged downstream of the process liquid source and upstream of the evaporator.

The fuel cell system according to the invention makes it possible to meter a process liquid such as water in particular (hereinafter also sometimes referred to as “process water”) separately from the fuel in the direction of the evaporator or evaporators. The process liquid and the fuel can be supplied to the at least one evaporator in a particularly simple and precise manner by means of the process liquid pump and the fuel pump arranged separately from it. More precisely, a process liquid / fuel ratio can be set to the desired mixing ratio in a particularly simple manner by means of the process liquid pump and the fuel pump. In this way, unnecessarily large storage tanks or a recirculation system designed for an unnecessarily strong fluid passage can be dispensed with. As a result, both the weight and the degree of complexity of the fuel cell system can be kept low. In addition, the costs for the fuel cell system can be kept correspondingly low.

The process liquid is understood in particular to be water in liquid form or water vapor, and the use or admixture of other substances is also possible. The process liquid can thus generally be understood to mean a water-containing fluid for the operation of the fuel cell system. The process water can have other fluid components in addition to water.

In the context of the present disclosure, an evaporator is understood to mean a component to which heat is supplied on the one hand and a medium to be evaporated on the other hand. The heat can be supplied, for example, by exhaust gas from the fuel cell stack, the hot exhaust gas and the medium to be evaporated (or a gaseous media stream in which the medium to be evaporated - for example process liquid and / or fuel) are spatially separated from one another.

According to the invention, the fuel source and the process liquid source are preferably arranged separately from one another. This makes it particularly easy to provide the process liquid and fuel separately. Experiments within the scope of the present invention have surprisingly shown that a separate configuration of the process liquid source and the fuel source compared to the possible disadvantages due to an increased weight and an increased degree of complexity compared to a single mixing tank brings decisive advantages with regard to the functioning of the fuel cell system ,

The fuel source is preferably a fuel tank in which fuel in the form of hydrogen, methane, ethanol, diesel, or a gas mixture, e.g. with one of the aforementioned substances.

The fuel pump can be understood as a fluid pump in the form of a hydraulic pump or a gas pump or a corresponding blower. The process liquid pump can also be understood to mean a fluid pump in the form of a hydraulic pump or a gas pump or a corresponding blower.

The fuel cell system is preferably designed as a SOFC system in which, using the process liquid and the fuel in the reformer, preferably hydrogen-containing fuel for the anode section of the fuel cell stack can or will be produced. For this purpose, the fuel cell stack can have a plurality of fuel cell stack sections. That is, the present invention is not limited to a fuel cell system that has only a single fuel cell stack.

It when two evaporators are provided, which are preferably, is particularly advantageous

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AT 519 833 B1 2020-02-15 Austrian patent office in the direction of the reformer, through which fuel and / or a process liquid can flow in series or parallel to evaporate the fuel and the process liquid separately. A mixture to a fuel mixture supplied to the fuel cell stack consequently takes place only after the evaporators and before the reformer. The two evaporators can preferably be flowed through in series or parallel by fuel and / or a process liquid in the direction of the reformer. The fuel and the process liquid are only mixed with one another in a gaseous state, as a result of which a desired mixing ratio can be set even more easily.

In a parallel arrangement of the evaporators, a first evaporator is designed to evaporate process liquid, for which purpose it is arranged upstream of the process liquid source and downstream of the process liquid pump. A second evaporator is designed to evaporate fuel and upstream of the process liquid source, in particular downstream of the first evaporator, the second evaporator being arranged downstream of the fuel pump. After the separate evaporation, the gaseous substances are mixed with one another downstream of the evaporators and upstream of the reformer to form the fuel mixture.

Alternatively, in a serial arrangement, the two evaporators can also be arranged downstream of the fuel pump or the process liquid pump and upstream of the reformer. A first evaporator is designed to evaporate process liquid and is arranged downstream of the process water pump and upstream of a second evaporator. In a first step, the process liquid is evaporated and in a second step the still liquid fuel of the gaseous process liquid is fed to the second evaporator, for example injected via an injector like a nozzle. The second evaporator is arranged in this arrangement downstream of the fuel pump and upstream of the reformer. It can also be provided that the first evaporator is designed to evaporate fuel and the liquid process liquid is then fed to the gaseous fuel in the second evaporator. In any case, it is particularly favorable if at least one of them is gaseous when the process liquid and the fuel are mixed.

According to a further development of the present invention, it is possible that an exhaust gas burner for burning anode exhaust gas and / or cathode exhaust gas is provided in a fuel cell system, which is in fluid communication with a condenser for condensing exhaust gas burner exhaust gas, the process liquid source providing the condenser for the Process liquid has. Experiments within the scope of the present invention have shown that condensed exhaust gas burner exhaust gas is easier to recirculate and with correspondingly less effort than untreated or gaseous exhaust gas burner exhaust gas. Using the condenser, the recirculation system can be made available in a correspondingly simple and effective manner. In this case, the process liquid pump can in particular be understood as a hydraulic pump. For condensing the exhaust gas burner exhaust gas, a cathode gas line can be routed along the condenser in order to heat the exhaust gas burner exhaust gas by means of a thermal interaction by means of cathode gas, in particular air, which must be heated anyway and is led to the cathode section. Due to the recirculation of condensed process liquid, only a small or theoretically no process liquid tank is required to store process liquid for the operation of the fuel cell system. This can save weight and costs.

Nevertheless, it is possible that in a fuel cell system according to the present invention, the process liquid source has a liquid tank for storing process liquid. The liquid tank is preferably smaller than the fuel tank. In particular, using the condenser described above, the liquid tank can be kept relatively small, since in principle process liquid is only required for starting operation of the fuel cell system when water is not yet generated by the fuel cell system. During operation of the fuel cell system, the

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Liquid tank can be used as a process liquid buffer for temporarily storing the process liquid or the water that is generated by the condenser. A heating device for heating the liquid tank can be provided for the liquid tank in order to prevent freezing of temporarily stored process liquid or water and thereby to ensure the functionality of the fuel cell system.

It can be a further advantage if the condenser in a fuel cell system according to the invention is arranged upstream of the liquid tank for supplying water condensate for use as process liquid to the liquid tank. As a result, an advantageous combination of the condenser and the liquid tank, as mentioned above, can be implemented in a simple manner. The condenser is preferably arranged directly or essentially directly upstream of the liquid tank.

It is also provided in a fuel cell system according to the invention that a fuel injector for injecting the fuel into an evaporator is arranged downstream of the fuel pump and a process liquid injector for injecting the process liquid into an evaporator is arranged downstream of the process liquid pump. That is, the process liquid injector is arranged in addition to the process liquid pump and the fuel injector is arranged in addition to the fuel pump. As a result, a mixing ratio of a fuel mixture consisting of the process liquid and the fuel can be set particularly easily. As a result, the fuel cell system can be operated correspondingly efficiently and / or effectively and flexibly adapted to the desired operating parameters. Using the two separate injectors, pressure losses in the respective fluid lines can also be kept low. If only one evaporator is provided, in which the process liquid and the fuel are evaporated together, the two injectors are arranged in separate fluid lines, i.e. the fuel injector in a fuel line for supplying the fuel from the fuel tank to the evaporator and the process liquid injector in a process liquid line for supplying the Process liquid from the liquid tank to the evaporator. The fuel injector and the process liquid injector can also be used advantageously for a quick and effective starting process of the fuel cell system, especially when a fuel such as ethanol is used. For a starting process of the fuel cell system, in which the fuel cell system is generally relatively cold, the mixing ratio of ethanol and water can be set to 55% ethanol to 45% water, for example. Ethanol evaporates faster than water at lower temperatures and accordingly requires less energy for an evaporation process. This can be used advantageously for an efficient and quick starting process if, for example, a heating device is used to preheat the fuel mixture. The separately arranged injectors can also be advantageous for a steam purging process of the fuel cell system and for different fuel mixture concepts. These advantages also apply if two evaporators are provided as described. Here, too, the two injectors are arranged in separate fluid lines, one injector for supplying the process liquid into a first evaporator and a second injector for supplying the fuel into a second evaporator.

In a further embodiment of the present invention, it is possible that in a fuel cell system according to the invention, downstream of the fuel pump and downstream of the process liquid pump and upstream of the evaporator, a mixing chamber for mixing the fuel with the process liquid is arranged, downstream of the mixing chamber and upstream of the evaporator a fuel mixture pump for supplying the fuel mixture to the evaporator is arranged. The fuel mixture can be premixed locally and flexibly in the mixing chamber before it is passed on by the fuel mixture pump in the direction of the evaporator. To inject the fuel mixture into the evaporator, a fuel mixture injector can be arranged on the evaporator, which is arranged downstream of the mixing chamber and downstream of the fuel mixture pump. The fuel mixture pump is as a Brenn4 / 18

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to understand the material mixture delivery unit in the form of a fluid pump or a gas pump or a blower. In order to lower the freezing point of the fuel mixture, a fuel mixture with a suitable mixing ratio can be provided in the mixing chamber. When using ethanol as fuel, a mixing ratio of 55% water to 45% ethanol has proven to be advantageous in order to lower the freezing point sufficiently, namely to approximately -35 ° C. As a result, the fuel cell system can be operated or started reliably even at low temperatures. Various devices and methods can be used to ensure the desired mixing ratio, for example a density determination unit for determining the density of the fuel mixture or a fuel mixing control device for controlling the injection behavior of the fuel injector and the process liquid injector.

Furthermore, in a fuel cell system according to the present invention, an exhaust gas burner for burning anode exhaust gas and / or cathode exhaust gas can be provided, which is in fluid communication with a condenser for condensing exhaust gas burner exhaust gas, the process liquid source having the condenser for providing the process liquid. The fuel cell system can be operated particularly efficiently using exhaust gas recirculation from the exhaust gas burner to the condenser. For a compact construction of the fuel cell system, the exhaust gas burner is preferably arranged in a ring around the reformer. This design also enables good heat transfer between the reformer and the exhaust gas burner.

According to a further aspect of the present invention, a motor vehicle with a fuel cell system for supplying energy to at least one drive unit of the motor vehicle is provided, the fuel cell system being designed as described in detail above. A motor vehicle according to the invention thus has the same advantages as have been described in detail with reference to the fuel cell system according to the invention. The motor vehicle is preferably designed as a (hybrid) electric vehicle.

Further measures improving the invention result from the following description of various exemplary embodiments of the invention, which are shown schematically in the figures. Each shows schematically:

Figure 1a a fuel cell system according to a first embodiment of the present invention, Figure 1b a first variant of the embodiment of the present invention from Figure 1a, Figure 1c a second variant of the embodiment of the present invention from Figure 1a, FIG. 2 a fuel cell system according to a second embodiment of the present invention, FIG. 3 a fuel cell system according to a third embodiment of the present invention, FIG. 4 a fuel cell system according to a fourth embodiment of the present invention, and FIG. 5 Motor vehicle with a fuel cell system according to an embodiment of the present invention.

Elements with the same function and mode of operation are each provided with the same reference numerals in FIGS. 1 to 5.

1a shows a block diagram for schematically illustrating a fuel cell system 100a according to a first embodiment. The fuel cell system 100a shown has a fuel cell stack 1 with an anode section 2 and one

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Cathode section 3. The fuel cell system also has a reformer 4 for supplying reformed anode gas to the anode section 2 and an evaporator 5 for evaporating a fuel mixture which is to be used in the reformer 4. An evaporator 5 is understood to mean a component to which heat is supplied on the one hand and a medium to be evaporated on the other, the heat being supplied spatially separate from the supply of the medium to be evaporated so that no mixing takes place - this is e.g. important if an exhaust gas is used to supply heat. An annular exhaust gas burner 14 is designed around the reformer 4 for burning anode exhaust gas and cathode exhaust gas.

The fuel cell system 100a also has a fuel source in the form of a fuel tank 6 for providing fuel for the fuel mixture in the reformer 4. In addition, the fuel cell system 100a has a process liquid source in the form of a liquid tank 7 and a condenser 8 upstream of the liquid tank 7 for providing process liquid for the fuel mixture in the reformer 4. That is, the condenser 8 is arranged upstream of the liquid tank 7 for supplying water condensate for use as the process liquid to the liquid tank 7. The condenser 8 is in fluid communication with the exhaust gas burner 14 for condensing exhaust gas burner exhaust gas. In the exemplary embodiment shown, water (“process water”) is used as the process liquid.

A fuel pump 9 for pumping the fuel from the fuel tank 6 to the evaporator 5 is arranged downstream of the fuel tank 6 and upstream of the evaporator 5. A process liquid pump 10 for pumping the process water from the liquid tank 7 to the evaporator 5 is arranged downstream of the liquid tank 7 and upstream of the evaporator 5.

A fuel injector 15 for injecting the fuel into the evaporator 5 is arranged downstream of the fuel pump 9. In addition, a process liquid injector 16 for injecting the process water into the evaporator 5 is arranged downstream of the process liquid pump 10. The fuel injector 15 and the process liquid injector 16 are arranged in two separate fluid lines. More precisely, the fuel injector 15 is arranged in or at the end of a fuel line which establishes a fluid connection between the fuel tank 6 and the evaporator 5. The process liquid injector 16 is arranged in or at the end of a process liquid line which establishes a fluid connection between the liquid tank 7 or the condenser 8 and the evaporator 5. The fuel injector 15 and the process liquid injector 16 are each designed as injection nozzles.

Upstream of the evaporator 5, a heat exchanger 17 is arranged, which is in fluid communication with both the evaporator 5 and with the exhaust gas burner 14, to which it is arranged downstream. The cathode and anode exhaust gas burned in the exhaust gas burner 14 is thus passed through the hot side of the heat exchanger 17 and then flows through the evaporator 5, where it evaporates the injected process water and the fuel, and further in the direction of an exhaust pipe. A fan 18 is arranged upstream of the heat exchanger 17, through which the cathode section 3 can be supplied with cathode gas in the form of air. The cathode gas flows through the cold side of the heat exchanger 17 and the exhaust gas flowing spatially separated through the hot side is heated. To heat the air, a cathode gas supply line is thermally operatively connected to the heat exchanger 17.

1b shows a further variant of a fuel cell system 100a from FIG. 1a, comprising two evaporators 5, 5a. The fuel and the process water can be evaporated separately from one another by the two evaporators 5, 5a. A mixture into a fuel mixture consequently takes place only after the evaporators 5, 5a and before or in the reformer 4. If the mixing takes place upstream of the reformer 4, the respective lines from the evaporators 5, 5a are brought together before the reformer 4. The fuel and the pro

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AT 519 833 B1 2020-02-15 Austrian patent office Zesswasser are only mixed together in a gaseous state. 1b, two evaporators 5, 5a are provided, which are arranged one after the other upstream of the process water source 8 (serial arrangement). A first evaporator 5 is designed to evaporate process water, for which purpose it is arranged upstream of the condenser 8 functioning as the process liquid source and downstream of the process liquid pump 10. A second evaporator 5a is designed to evaporate fuel and is arranged upstream of the process liquid source 8, in particular upstream of the first evaporator 5 and downstream of the fuel pump 9. After the separate evaporation, the gaseous substances downstream of the evaporators 5, 5a and upstream of the reformer 4 are mixed with one another to form the fuel mixture. The exhaust gas flow from the exhaust gas burner 14 first flows through the heat exchanger 17 and then sequentially through the second evaporator 5a and the first evaporator 5 before the exhaust gas flow is fed to the process liquid source in the form of the condenser 8 or the process liquid source in the form of the liquid tank 7.

In an additional embodiment, not shown, of the variant according to FIG. 1b, the exhaust gas flow from the exhaust gas burner 14 can be divided into two lines either before or after the heat exchanger 17. A first line leads through the first evaporator 5 and a second line leads through the second evaporator 5a, so that the two evaporators 5 and 5a are flowed through in parallel by the exhaust gas stream. Downstream of the evaporators 5, 5a, the two exhaust gas streams are brought together again to form one exhaust gas stream. However, it can also be provided that these are fed separately to the process liquid source designed as a condenser 8.

1c shows a further variant: the two evaporators 5, 5a are in turn arranged downstream of the fuel pump 9 or the process liquid pump 10 and upstream of the reformer 4. A first evaporator 5 is designed to evaporate process water and is arranged upstream of the process liquid pump 9 and also upstream of a second evaporator 5a. In a first step, the process water is evaporated and in a second step the liquid fuel is fed to the gaseous process water in the second evaporator 5a, for example injected via an injector 15. An injector 16 can also be provided for introducing process water into the first evaporator 5. It can also be provided that the first evaporator 5 is designed to evaporate fuel and the liquid process water is then fed to the gaseous fuel in the second evaporator 5a. In any case, it is particularly favorable if at least one of the components thereof is gaseous when the process water and fuel are mixed.

1c shows a variant with solid lines, in which the exhaust gas coming from the heat exchanger 17 is only passed through the first evaporator 5 and the medium introduced there evaporates. The second evaporator 5a does not have a separate heat source, but the evaporated medium from the first evaporator 5 serves as a heat source for the medium introduced into the second evaporator 5a, which also evaporates.

A further variant is shown in Fig. 1c with dashed lines: After the heat exchanger 17, the exhaust pipe divides and supplies both the first evaporator 5 and the second evaporator 5a with hot exhaust gas, so that the media introduced evaporates due to the exhaust gas heat become.

2 shows a fuel cell system 100b according to a second embodiment. To avoid redundant parts of the description, only the distinguishing features of the fuel cell system 100b from the above-described first embodiment will be described. In the fuel cell system 100b shown in FIG. 2, the liquid tank 7 has been dispensed with. Correspondingly, condensed process water can be fed from the condenser 8 directly to the evaporator 5 by means of the process liquid pump 10 and there injected into the evaporator 5 by the process liquid injector 16. In addition, the embodiment according to FIG. 2 can also have two evaporators 5, 5a

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AT 519 833 B1 2020-02-15 Austrian patent office, which can be arranged according to Fig. 1b or Fig. 1c.

3 shows a fuel cell system 100c according to a third embodiment. To avoid redundant parts of the description, only the distinguishing features of the fuel cell system 100c from the above-described embodiments are described below. In the fuel cell system 100c shown in FIG. 3, a mixing chamber 11 for mixing the fuel with the process water is arranged downstream of the fuel pump 9 and downstream of the process liquid pump 10 and upstream of the evaporator 5, a fuel mixture pump being arranged downstream of the mixing chamber 11 and upstream of the evaporator 5 12 for supplying the fuel mixture to the evaporator 5 is arranged. A fuel mixture injector 13 is arranged on the evaporator 5 for injecting the fuel mixture into the evaporator 5.

4 shows a fuel cell system 100d according to a fourth embodiment. To avoid redundant parts of the description, only the distinguishing features of the fuel cell system 100d from the above-described third embodiment are described below. In the fuel cell system 100d shown in FIG. 4, the liquid tank 7 has been dispensed with. Correspondingly, condensed process water can be passed from the condenser 8 via the mixing chamber to the evaporator 5 without going through the liquid tank 7.

5 shows a motor vehicle 1000 configured as an electric vehicle with a fuel cell system 100a as described above for supplying energy to an electric motor 200 of the motor vehicle 1000.

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LIST OF REFERENCE NUMBERS

fuel cell stack

anode section

cathode portion

reformer

Evaporator

5a second evaporator

Fuel tank (fuel source)

Liquid tank (process liquid source)

Condenser (process liquid source)

fuel pump

Process liquid pump

mixing chamber

Fuel mixture pump

Fuel mixture injector

exhaust gas burner

fuel injector

Prozessflüssigkeitsinjektor

heat exchangers

fan

100a to 100d fuel cell system

200 electric motor (drive unit)

1000 motor vehicles

Claims (9)

1. Fuel cell system (100a; 100b; 100c; 100d), comprising a fuel cell stack (1) with an anode section (2) and a cathode section (3), a reformer (4) for pre-reforming a fuel supplied to the fuel cell stack, at least one evaporator (5 ) for vaporizing a fuel and / or a process liquid for use in the reformer (4), a fuel source (6) for providing fuel for a fuel mixture in the reformer (4), and a process liquid source (7, 8) for providing process liquid for the Fuel mixture in the reformer (4), a fuel pump (9) for pumping the fuel from the fuel source (6) to the evaporator (5) downstream of the fuel source (6) and upstream of the at least one evaporator (5), and downstream of the process liquid source (7 , 8) and upstream of the at least one evaporator (5) a process liquid pump (10) for pumping the process liquid t from the process liquid source (7, 8) to the evaporator (5), characterized in that a fuel injector (15) for injecting the fuel into the evaporator (5) is arranged downstream of the fuel pump (9) and downstream of the process liquid pump (10 ) a process liquid injector (16) for injecting the process liquid into the evaporator (5) is arranged. 2. The fuel cell system (100a; 100b; 100c; 100d) according to claim 1, characterized in that two evaporators (5, 5a) are provided which can be flowed through in series or parallel by fuel and / or a process liquid, preferably in the direction of the reformer (4) are. 3. Fuel cell system (100a; 100b; 100c; 100d) according to one of the preceding claims, characterized in that an exhaust gas burner (14) for burning anode exhaust gas and / or cathode exhaust gas is provided, which is provided with a condenser (8) for condensing exhaust gas burner Exhaust gas is in fluid communication, the process liquid source having the condenser (8) for providing the process water. 4. Fuel cell system (100a; 100c) according to one of the preceding claims, characterized in that the process liquid source has a liquid tank (7) for storing process liquid. 5. Fuel cell system (100a; 100c) according to claim 4, characterized in that the condenser (8) is arranged upstream of the liquid tank (7) for supplying liquid, in particular water condensate for use as process liquid to the liquid tank (7). 6. Fuel cell system (100c; 10Od) according to claim 1, characterized in that downstream of the fuel pump (9) and downstream of the process liquid pump (10) and upstream of the evaporator (5) a mixing chamber (11) for mixing the fuel with the process liquid A fuel mixture pump (12) for supplying the fuel mixture to the evaporator (5) is arranged downstream of the mixing chamber (11) and upstream of the evaporator (5). 7. Fuel cell system (100c; 10Od) according to one of claims 1 to 6, characterized in that an exhaust gas burner (14) for burning anode exhaust gas and / or cathode exhaust gas is provided, which with a condenser (8) for condensing exhaust gas burner exhaust gas into There is a fluid connection, the process liquid source having the condenser (8) for providing the process liquid. 10/18 AT 519 833 B1 2020-02-15 Austrian patent office 8. Fuel cell system (100c) according to one of the preceding claims, characterized in that the process liquid source has a liquid tank (7) for storing process liquid, in particular the condenser (8) upstream of the liquid tank (7) for supplying liquid, in particular water condensate is arranged for use as a process liquid to the liquid tank (7). 9. Motor vehicle (1000) with a fuel cell system (100a; 100b; 100c; 100d) for supplying energy to at least one drive unit (200) of the motor vehicle (1000), the fuel cell system (100a; 100b; 100c; 100d) being designed according to one of the preceding claims is.