DE102021213088A1 - Process for drying a fuel cell system - Google Patents

Abstract

The invention relates to a method for drying a fuel cell system (100), in particular a fuel cell stack (101) of the fuel cell system (100), in particular when the fuel cell system (100) is switched off, at a standstill, in standby mode and/or in start-stop mode Fuel cell system (100), preferably in preparation for a start, in particular a freeze start, of the fuel cell system (100), comprising: - shutting off a cathode path (K) of the fuel cell system (100), - initiating a recirculation operation (opZ) in the cathode path (K) , in particular through a bypass line (13) of a cathode system (10), - homogenization and inerting of a cathode gas enclosed in the cathode path (K) by the recirculation mode (opZ).

Description

The invention relates to a method for drying a fuel cell system, in particular a fuel cell stack of the fuel cell system, in particular when the fuel cell system is switched off, at a standstill, in standby mode and/or in start-stop mode, preferably in preparation for a start. in particular a freeze start of the fuel cell system. In addition, the invention relates to a corresponding fuel cell system.

State of the art

• - funktional zu realisieren und
• - dabei die Lebenszeitanforderungen an das System zu erreichen.

In vehicles, so-called fuel cell vehicles, in which the drive energy is supplied by one or more fuel cell systems, among other things, the oxidizing agent oxygen from the ambient air and the reducing agent or fuel hydrogen are used to convert water (or water vapor) in the fuel cell. to react and thus to deliver electrical power through electrochemical conversion. The fuel cell systems usually include several fuel cells that are combined to form a stack. With mobile fuel cell systems, the challenge is starting the system under all globally relevant conditions and with different lengths of vehicle downtime:

• - to implement functionally and
• - while achieving the lifetime requirements for the system.

• - Ausblasen des Kathodenpfades durch das Luftverdichtungssystem, und/oder
• - Spülen des Anodenpfades mit trockenem Wasserstoff während der Stillstandphase des Systems.

A critical starting case is the freeze start (at low temperatures < 0°C), since in this case both the resulting water of reaction can freeze and the moisture previously formed during the standstill phase can condense out and freeze. The water can freeze in the system and cover the essential functional components of the system with ice. States and operating modes before the start are therefore essential in order to ensure preparatory measures for the restart, such as e.g. e.g.:

• - purging of the cathode path by the air compression system, and/or
• - Purge the anode path with dry hydrogen during the system shutdown phase.

Disclosure of Invention

The present invention provides: a method for drying a fuel cell system, in particular a fuel cell stack of the fuel cell system, in particular when the fuel cell system is switched off, at a standstill, in standby mode and/or in start-stop mode, preferably in preparation for a start, in particular a freeze start, of the fuel cell system, with the features of the independent method claim. In addition, the invention provides a corresponding fuel cell system with the features of the independent system claim. Features and details that are described in connection with the different embodiments and/or aspects of the invention also apply, of course, in connection with the other embodiments and/or aspects and vice versa, so that the disclosure of the individual embodiments and/or aspects is reversed is or can always be mutually referred to.

According to the first aspect, the present invention provides: a method for drying a fuel cell system, in particular a fuel cell stack of the fuel cell system, in particular when the fuel cell system is switched off, at a standstill, in standby mode and/or in start-stop mode, preferably in preparation for a start, in particular a freeze start, of the fuel cell system.

• - Absperren eines Kathodenpfades des Brennstoffzellensystems,
• - Einleiten eines Rezirkulationsbetriebes in dem Kathodenpfad, insbesondere durch eine Bypass-Leitung eines Kathodensystems,
• - Homogenisieren (bzw. Vergleichmäßigen) und Inertisieren (bzw. Sauerstoffverarmung) eines in dem Kathodenpfad eingeschlossenen Kathodengases durch den Rezirkulationsbetrieb.

The procedure has the following steps:

• - shutting off a cathode path of the fuel cell system,
• - Initiating a recirculation operation in the cathode path, in particular through a bypass line of a cathode system,
• - Homogenization (or equalization) and inerting (or oxygen depletion) of a cathode gas enclosed in the cathode path by the recirculation mode.

The fuel cell system according to the invention can preferably be used for mobile applications, for example in vehicles, in particular fuel-powered vehicles. The fuel cell system according to the invention can serve as the main energy supplier for a vehicle. At the same time, however, it is also conceivable that the fuel cell system according to the invention can serve as an energy supplier for an auxiliary drive and/or auxiliary drive of a vehicle, for example a hybrid vehicle. The fuel cell system according to the invention can also be used for stationary applications, for example in generators.

The fuel cell system according to the invention can have one or more stacks, each with a number of stacked fuel cells and the associated functional systems, comprising: media systems (air or cathode system, fuel or anode system, cooling system) and an electrical system.

The idea of the invention is that a homogeneous drying of the fuel cell system is provided. Drying the fuel cell system may include drying the cathode path and, if necessary, the anode path through the fuel cell stack. In addition to the cathode gas, homogeneous drying and inerting relate to the associated components of the fuel cell system, such as in particular the membrane (MEA, membrane electrode assembly), the gas diffusion layers, the surfaces of the channels and distributors. For this purpose, the invention provides that after the system has been switched off, the cathode path has been blown out if necessary, and the cathode path has been shut off, the cathode gas trapped in the cathode path is recirculated and inerted, i.e. oxygen depleted, in order to homogenize the moisture distribution on the cathode side of the system or to compare. The inventive concept also provides that the water produced during inerting/oxygen depletion on the cathode side, which also enables rewetting of the membrane - if the blow-out process previously caused the membrane to be too dry in places or overall - is evenly distributed. The recirculation of the cathode gas trapped in the cathode path also reduces the peaks in the moisture distribution. In this way, the cathode path can be dried, at least indirectly. In addition, a desiccant, comprising e.g. zeolite, silica gel, silica gel or similar, can be arranged in the cathode path, preferably in a path capable of recirculation, e.g. through a bypass line, in order to achieve direct drying by lowering the average humidity from the in to allow the cathode gas trapped in the cathode path. In addition, the drying of the system can be supported by a recirculation of an anode gas enclosed in the anode path. At this time, a higher pressure can be set on the anode side than on the cathode side in order to cause the water to be pressed from the anode side to the cathode side and the air not to permeate from the cathode side to the anode side. Furthermore, a cooling system can be switched on as a support in order to encourage the water to condense out and to support the absorption of the water in the desiccant. If required, the desiccant can be blown out or regenerated with dry, hot air and, if necessary, using an (optional) electric heater. This can take place before or after the drying of the fuel cell stack, possibly also during normal operation of the fuel cell system.

The method can be carried out with all system topologies that have a path capable of recirculation in the cathode system. A path capable of recirculation in the cathode system can be implemented, for example, by a bypass line, which is used to direct the supply air at least partially past the stack. The path capable of recirculation can have its own conveyor, e.g. compressor, or can be operated using existing conveyors in the cathode system.

The method can be carried out when the fuel cell system is at a standstill, in standby mode and/or in start-stop mode, preferably in preparation for a start, in particular a freeze start, of the fuel cell system.

In the case of longer periods of standstill, the process can be triggered using a wake-up function. Furthermore, the method can be triggered at specific time intervals. Furthermore, the method can be triggered when the temperature falls below certain thresholds. Advantageously, the method can represent a consumption-friendly alternative to parking purge, which significantly reduces fuel consumption.

The process can be used to improve the drying of the stack on the anode and cathode side. In addition, the process enables a reduction in fuel losses. In addition, the process improves the preparation for a freezing start (homogenization + drying). Furthermore, the method enables flexible coverage of many operating modes of the system, e.g. shutdown/stopping, inerting/bleed-down, standby, start-stop, operation in standstill phases, wake-up, etc.

• - Durchführen des in dem Kathodenpfad eingeschlossenen Kathodengases durch ein Trocknungsmittel in dem Kathodenpfad.

The method can also include:

• - passing the cathode gas trapped in the cathode path through a desiccant in the cathode path.

In this way, the average humidity from the cathode gas enclosed in the cathode path can be reduced directly and/or actively. The drying of the fuel cell system, in particular of the stack, can be improved in this way.

The desiccant can be arranged, for example, in a path of the cathode system capable of recirculation, for example in a bypass line. Such an arrangement of the desiccant has no negative impact on the system design, on the performance of the system, since no additional pressure losses in the cathode path are caused by the stack.

• - Rezirkulieren eines in dem Anodenpfad eingeschlossenen Anodengases. Auf diese Weise kann die Homogenisierung der Feuchte auf der Anodenseite bewirkt werden und der Wassertransport auf die Kathodenseite begünstigt werden.

Furthermore, the method can have:

• - recirculating an anode gas trapped in the anode path. In this way, the moisture can be homogenized on the anode side and the transport of water to the cathode side can be promoted.

Advantageously, when carrying out the method, a specific, in particular decreasing, pressure difference can be adjusted between an anode space and a cathode space of the fuel cell system. Thus, air can be prevented from permeating from the cathode side to the anode side. In addition, this can cause the moisture to be displaced to the cathode side, where it can be transported away better.

• - Betreiben eines Kühlsystems des Brennstoffzellensystems.

In addition, the method can include:

• - Operating a cooling system of the fuel cell system.

This can promote the condensation of the water, so that the water can be better transported away and/or absorbed by a desiccant.

• - Durchführen eines Regenerationsbetriebs eines Trocknungsmittels in dem Kathodenpfad, insbesondere über eine Bypass-Leitung, vorzugsweise zum Entfeuchten des Trocknungsmittels.

Advantageously, the method can also have a mode for regenerating the desiccant. For this purpose, the method can have:

• - Carrying out a regeneration operation of a desiccant in the cathode path, in particular via a bypass line, preferably for dehumidifying the desiccant.

To carry out the regeneration operation, the stack can remain closed and the desiccant can be blown free with dry, hot air (approx. 120°C to 150°C). This can also happen in normal operation if z. B. part of the supply air is derived through the bypass line.

• - Ausblasen des Kathodenpfades des Brennstoffzellensystems.

Furthermore, it can be advantageous if at least one step is carried out before carrying out the method or before shutting down the system, in particular before shutting off a cathode path of the fuel cell system:

• - Blow out the cathode path of the fuel cell system.

In this way, the moisture present in the system can be at least partially removed before the system is shut down.

• - mindestens einen Brennstoffzellenstack,
• - ein Kathodensystem zum Bereitstellen eines Kathodengases zum Bren nstoffzel lenstack, wobei das Kathodensystem mit einem rezirkulationsfähigen Pfad ausgeführt ist, welcher insbesondere mithilfe einer Bypass-Leitung zu einem Kathodenpfad durch den Brennstoffzellenstack gebildet ist,
• - und eine Steuereinheit zum Ansteuern des Brennstoffzellensystems, wobei die Steuereinheit dazu ausgeführt ist, ein Verfahren wie oben beschrieben durchzuführen, welches zum Trocknen eines Brennstoffzellensystems, vorzugsweise eines Brennstoffzellenstacks des Brennstoffzellensystems, insbesondere bei einem Abstellen, bei einem Stillstand, bei einem Standby-Betrieb und/oder bei einem Start-Stopp-Betrieb des Brennstoffzellensystems, vorzugsweise in Vorbereitung auf einen Start, insbesondere einen Gefrierstart, des Brennstoffzellensystems dient.

According to the second aspect, the present invention provides: a fuel cell system, comprising:

• - at least one fuel cell stack,
• - a cathode system for providing a cathode gas to the fuel cell stack, the cathode system being designed with a path capable of recirculation, which is formed in particular with the aid of a bypass line to a cathode path through the fuel cell stack,
• - and a control unit for controlling the fuel cell system, wherein the control unit is designed to carry out a method as described above, which is used to dry a fuel cell system, preferably a fuel cell stack of the fuel cell system, in particular when it is switched off, when it is at a standstill, when it is in standby mode and /or in a start-stop operation of the fuel cell system, preferably in preparation for a start, in particular a freeze start, of the fuel cell system.

The system according to the invention achieves the same advantages as described above in connection with the method according to the invention. Reference is made in full to these advantages here.

A desiccant can advantageously be provided in the cathode system, in particular in the bypass line to the cathode path. The desiccant can be used to lower the moisture from the cathode exhaust gas.

• - das Trocknungsmittel in der Bypass-Leitung integriert ist,
• - das Trocknungsmittel ein wasserabsorbierendes Material, bspw. Zeolith, Silicagel, Kieselgel, usw. aufweist, insbesondere wobei das wasserabsorbierende Material pulvrig, körnig und/oder shüttgutartig ausgeführt ist, und/oder wobei das wasserabsorbierende Material offenporös ausgeführt ist, und/oder wobei das wasserabsorbierende Material eine vergrößerte Oberfläche für einen verbesserten fluidischen Kontakt zum Kathodengas bildet, um ein Beladen und Abgeben von Feuchtigkeit von dem Trocknungsmittel zu begünstigen,
• - das Trocknungsmittel einen, insbesondere gitterartigen und/oder siebartigen, Rohreinsatz aufweist, insbesondere wobei der Rohreinsatz zumindest zum Teil zylindermantelförmig und/oder hülsenförmig ausgeführt ist, und/oder wobei der Rohreinsatz zumindest zum Teil umfangsseitig in der Bypass-Leitung angeordnet ist, und/oder wobei der Rohreinsatz zumindest zum Teil den Querschnitt der Bypass-Leitung, bspw. teilkreisförmig und/oder sektorförmig, abdeckt, und/oder wobei der Rohreinsatz ein wasserabsorbierendes Material aufnimmt, und/oder
• - das Trocknungsmittel mindestens einen, insbesondere gitterartigen und/oder siebartigen, Injektor aufweist, insbesondere wobei der Injektor endoskopisch in die Bypass-Leitung integriert ist, und/oder wobei der Injektor ein wasserabsorbierendes Material aufnimmt.

It is also conceivable that:

• - the desiccant is integrated in the bypass line,
• - the desiccant has a water-absorbing material, e.g. zeolite, silica gel, silica gel, etc., in particular where the water-absorbing material is powdery, granular and/or bulky, and/or where the water-absorbing material is open-pored, and/or where the water-absorbing material has an increased surface area for improved fluidic contact with the catho forms dengas to promote loading and shedding of moisture from the desiccant,
• - the desiccant has a, in particular grid-like and/or sieve-like, tube insert, in particular wherein the tube insert is designed at least partially in the shape of a cylinder jacket and/or sleeve-shaped, and/or wherein the tube insert is arranged at least partially on the peripheral side in the bypass line, and/ or wherein the pipe insert at least partially covers the cross section of the bypass line, e.g. partially circular and/or sector-shaped, and/or wherein the pipe insert accommodates a water-absorbing material, and/or
• - the desiccant has at least one injector, in particular a grid-like and/or sieve-like injector, in particular the injector being integrated endoscopically into the bypass line, and/or the injector receiving a water-absorbing material.

In this way, a simple and cost-effective desiccant can be provided, which can reliably reduce the moisture from the cathode exhaust gas.

In addition, in the fuel cell system, a heater can be provided in the cathode system, in particular in the bypass line to the cathode path, preferably parallel to a desiccant. The heater can be operated to support the regeneration of the desiccant. However, the heater can also be used to raise the temperature on the cathode side when starting to freeze.

character list

• 1 ein beispielhaftes Brennstoffzellensystem mit einem möglichen rezirkulationsfähigen Pfad in einem Kathodensystem,
• 2 ein beispielhaftes Brennstoffzellensystem mit einem weiteren möglichen rezirkulationsfähigen Pfad in einem Kathodensystem, und
• 3 ein beispielhaftes Brennstoffzellensystem mit einem weiteren möglichen rezirkulationsfähigen Pfad in einem Kathodensystem.

The invention and its developments as well as its advantages are explained in more detail below with reference to drawings. They each show schematically:

• 1 an exemplary fuel cell system with a possible recirculation-capable path in a cathode system,
• 2 an example fuel cell system with another possible recyclable path in a cathode system, and
• 3 an example fuel cell system with another possible recyclable path in a cathode system.

In the different figures, the same parts of the invention are always provided with the same reference numerals, which is why these i. i.e. R. only be described once.

The 1 until 3 FIG. 1 shows an exemplary fuel cell system 100 within the scope of the invention. The fuel cell system 100 mostly comprises a plurality of fuel cells which are combined to form a fuel cell stack or stack 101 . In addition, fuel cell system 100 includes at least four functional systems, including: a cathode system 10 to supply a cathode space or a cathode path K of stack 101 with an oxygen-containing gas mixture, an anode system 20 to supply an anode space or an anode path A of stack 101 with a to supply fuel-containing gas mixture, a cooling system 30 to temper the stack 101, and an electrical system (not shown for reasons of simplicity) to dissipate the generated electrical power from the stack 101.

The cathode system 10 comprises an air supply line 11 to the stack 101 and an exhaust air line 12 from the stack 101. An air filter AF is usually arranged at the inlet of the air supply line 11 in order to filter harmful chemical substances and particles or to prevent them from entering the system 100. The gas pumping machine V in the cathode system 10 can be designed in the form of a compressor in order to draw in the air from the environment U and provide it to the stack 101 in the form of supply air. After passing through the stack 101, an exhaust air is discharged from the system 100 to the environment U again. Like it the 1 indicates, a heat exchanger HE and/or an inlet air cooler IC can/can be arranged downstream of the gas conveying machine V. Shutoff valves SV1, SV2 can be provided before and after the stack 101. In addition, a separate valve CVexh can be provided in the exhaust air line 12 as a pressure regulator. Like it the 1 indicates, the pressure regulator can be integrated in the shut-off valve SV2. A bypass line 13 with a ByCath bypass valve is provided between the supply air line 11 and the exhaust air line 12 . A path capable of recirculation can be provided in the cathode system 10 with the aid of the bypass line 13 , which path runs through the cathode space in the stack 101 .

The anode system 20 has several components. The components used to supply fuel include a fuel tank 21 and at least one pressure regulator 22. The pressure regulator 22 can also have a shut-off function. If the pressure regulator 22 does not have a shut-off function, a separate shut-off valve can be provided at the entrance to the anode chamber or anode path A. Other components in the anode system 20 are a jet pump 23 and a recirculation pump 24. In addition, in the ano densystem 20 a purge and / or drain valve 25 may be provided.

The 2 and 3 show other possible topologies of the fuel cell system 100, which can have recirculation-capable paths in the cathode system 10. Further variants of paths capable of recirculation in the cathode system 10 are of course conceivable. For example, paths capable of recirculation are conceivable, which can have their own gas extraction machine.

• - Absperren eines Kathodenpfades K des Brennstoffzellensystems 100, insbesondere mithilfe der Absperrventile SV1, SV2,
• - Einleiten eines Rezirkulationsbetriebes opZ in dem Kathodenpfad K, bspw. durch eine Bypass-Leitung 13 eines Kathodensystems 10,
• - Homogenisieren bzw. Vergleichmäßigen und Inertisieren eines in dem Kathodenpfad K eingeschlossenen Kathodengases durch den Rezirkulationsbetrieb opZ und vorzugsweise der damit zusammenhängenden Komponenten, insbesondere der Membran (MEA, membrane electrode assembly), der Gasdiffusionslagen und der Kanal-Oberflächen der Verteilerstrukturen.

The 1 until 3 serve to explain a method within the meaning of the invention, which is used to dry a fuel cell system 100, in particular a fuel cell stack 101 of the fuel cell system 100, in particular when it is switched off, at a standstill, in a standby mode and/or in a start-stop mode of the Fuel cell system, preferably in preparation for a start, in particular a freeze start, the fuel cell system 100 is used. The procedure has the following steps:

• - Shut off a cathode path K of the fuel cell system 100, in particular using the shut-off valves SV1, SV2,
• - Initiation of a recirculation operation opZ in the cathode path K, e.g. through a bypass line 13 of a cathode system 10,
• - Homogenizing or equalizing and inertizing a cathode gas enclosed in the cathode path K by the recirculation operation opZ and preferably the associated components, in particular the membrane (MEA, membrane electrode assembly), the gas diffusion layers and the channel surfaces of the distributor structures.

The recirculation operation opZ can preferably be carried out using a turbine T, which is coupled to the gas extraction machine V in the cathode system 10 . To carry out the recirculation operation opZ, the turbine T can be operated in the opposite direction than in normal operation opN of the system 100. During the recirculation operation opZ, the compressor wheel can be operated in mild-surge operation (rotating stall) due to the closed check valve SV1, which is not critical for reasons of component protection.

At the same time, however, it is also conceivable that a separate gas pumping machine (not shown) can be provided in the bypass line 13 in order to provide a path capable of recirculation in the cathode system 10 and to be able to carry out the recirculation operation opZ.

The invention can be used to provide homogeneous drying of the fuel cell system 100, for example when it is switched off, at a standstill, in a standby mode and/or in a start-stop mode. The drying of the fuel cell system 100 can include the drying of the cathode path 10 and, if necessary, the anode path 20 that lead through the stack 101 . For this purpose, the invention provides that after shutting down the system 100, possibly blowing out the cathode path 10, and shutting off the cathode path 10, the cathode gas enclosed in the cathode path K is recirculated in the recirculation mode opZ. In this way, the moisture distribution on the cathode side of the system 100 can be homogenized or made more uniform. The recirculation of the cathode gas enclosed in the cathode path K also reduces the peaks in the moisture distribution. In this way, the cathode path K can be dried, at least indirectly. In this way, the water produced during inerting can also be equalized. In this way, the areas of the membrane that are too dry, caused by the previous blow-out drying process, can also be remoistened.

Like it the 2 and 3 indicate, a desiccant TM comprising, for example, zeolite, silica gel, silica gel or the like can also be arranged in the recirculable path, preferably in the bypass line 13, in order to enable direct drying of the cathode gas by lowering the humidity.

In addition, the drying of the system 100 can be supported by a recirculation of an anode gas enclosed in the anode path A. A higher pressure can be set on the anode side than on the cathode side. In this way, the water can be caused to be pressed from the anode side to the cathode side and the air not to permeate from the cathode side to the anode side.

Furthermore, the cooling system 30 can be switched on as a support in order to encourage the water to condense out and to support the absorption of the water in the desiccant TN.

Like it the 2 and 3 show by means of arrows opR, the desiccant TM can be blown dry in a regeneration operation opR, preferably with a hot air, e.g. B, in a temperature range of 120 °C to 150 °C. In this case, the stack 101 can remain closed. To blow out the desiccant TM, the gas pumping machine V in the cathode system 10 be used. Like it the 2 and 3 also indicate that the regeneration operation opR of the desiccant TM can be assisted by means of an optional electric heater HT as needed. The regeneration operation opR of the desiccant TM can take place before or after the drying of the stack 101, possibly also during normal operation opN of the fuel cell system 100.

In the case of longer periods of standstill, the process can be triggered using a wake-up function. Furthermore, the method can be triggered at specific time intervals. Furthermore, the method can be triggered when the temperature falls below certain thresholds. Advantageously, the method can represent a consumption-friendly alternative to parking purge, which significantly reduces fuel consumption.

• - mindestens einen Brennstoffzellenstack 101,
• - ein Kathodensystem 10 zum Bereitstellen eines Kathodengases zum Brennstoffzellenstack 101, wobei das Kathodensystem 10 mit einem rezirkulationsfähigen Pfad ausgeführt ist, welcher insbesondere mithilfe einer Bypass-Leitung 13 zu einem Kathodenpfad K durch den Brennstoffzellenstack 101 gebildet ist,
• - und eine Steuereinheit 102 zum Ansteuern des Brennstoffzellensystems 100, wobei die Steuereinheit 102 dazu ausgeführt ist, ein Verfahren wie oben beschrieben durchzuführen, welches zum Trocknen eines Brennstoffzellensystems 100 bzw. Brennstoffzellenstacks 101, insbesondere bei einem Abstellen, bei einem Stillstand, bei einem Standby-Betrieb und/oder bei einem Start-Stopp-Betrieb des Brennstoffzellensystems 100, vorzugsweise in Vorbereitung auf einen Start, insbesondere einen Gefrierstart, des Brennstoffzellensystems 100 dient.

A corresponding fuel cell system 100 also represents an aspect of the invention, comprising:

• - at least one fuel cell stack 101,
• - a cathode system 10 for providing a cathode gas to the fuel cell stack 101, wherein the cathode system 10 is designed with a path capable of recirculation, which is formed in particular with the aid of a bypass line 13 to a cathode path K through the fuel cell stack 101,
• - And a control unit 102 for controlling the fuel cell system 100, wherein the control unit 102 is designed to carry out a method as described above, which is used to dry a fuel cell system 100 or fuel cell stack 101, in particular when it is switched off, when it is at a standstill, when it is on standby Operation and / or in a start-stop operation of the fuel cell system 100, preferably in preparation for a start, in particular a freeze start, the fuel cell system 100 is used.

Advantageously, a desiccant TM can be provided in the cathode system 10, in particular in the bypass line 13 to the cathode path K, in order to reduce the moisture in the cathode exhaust gas.

• - das Trocknungsmittel TM in der Bypass-Leitung 13 integriert ist,
• - das Trocknungsmittel TM ein wasserabsorbierendes Material, bspw. Zeolith, Silicagel, Kieselgel, usw. aufweist, insbesondere wobei das wasserabsorbierende Material pulvrig, körnig und/oder shüttgutartig ausgeführt ist, und/oder wobei das wasserabsorbierende Material offenporös ausgeführt ist, und/oder wobei das wasserabsorbierende Material eine vergrößerte Oberfläche für einen verbesserten fluidischen Kontakt zum Kathodengas bildet, um ein Beladen und Abgeben von Feuchtigkeit von dem Trocknungsmittel TM zu begünstigen,
• - das Trocknungsmittel TM einen, insbesondere gitterartigen und/oder siebartigen, Rohreinsatz aufweist, insbesondere wobei der Rohreinsatz zumindest zum Teil zylindermantelförmig und/oder hülsenförmig ausgeführt ist, und/oder wobei der Rohreinsatz zumindest zum Teil umfangsseitig in der Bypass-Leitung 13 angeordnet ist, und/oder wobei der Rohreinsatz zumindest zum Teil den Querschnitt der Bypass-Leitung 13, bspw. teilkreisförmig und/oder sektorförmig, abdeckt, und/oder wobei der Rohreinsatz ein wasserabsorbierendes Material aufnimmt, und/oder
• - das Trocknungsmittel TM mindestens einen, insbesondere gitterartigen und/oder siebartigen, Injektor aufweist, insbesondere wobei der Injektor endoskopisch in die Bypass-Leitung 13 integriert ist, und/oder wobei der Injektor ein wasserabsorbierendes Material aufnimmt.

With the desiccant TM it is conceivable: that:

• - the desiccant TM is integrated in the bypass line 13,
• - the desiccant TM has a water-absorbing material, e.g. zeolite, silica gel, silica gel, etc., in particular where the water-absorbing material is powdery, granular and/or bulky, and/or where the water-absorbing material is open-pored, and/or where the water-absorbing material provides an increased surface area for improved fluidic contact with the cathode gas to promote loading and shedding of moisture from the desiccant TM,
• - the desiccant TM has a pipe insert, in particular a grid-like and/or sieve-like pipe insert, in particular with the pipe insert being at least partially in the form of a cylinder jacket and/or sleeve-shaped, and/or with the pipe insert being arranged at least partly on the peripheral side in the bypass line 13, and/or wherein the pipe insert at least partially covers the cross section of the bypass line 13, e.g. partially circular and/or sector-shaped, and/or wherein the pipe insert accommodates a water-absorbing material, and/or
• - the desiccant TM has at least one, in particular grid-like and/or sieve-like, injector, in particular wherein the injector is endoscopically integrated into the bypass line 13, and/or wherein the injector accommodates a water-absorbing material.

As already mentioned above, in the fuel cell system a heater HT can be provided in the cathode system 10, in particular in the bypass line 13 to the cathode path K, preferably parallel to a desiccant TM. The heater HT can be operated to support the regeneration of the desiccant. However, the heater HT can also be useful during the freeze start of the system 100.

The above description of the figures describes the present invention exclusively within the framework of examples. It goes without saying that individual features of the embodiments can be freely combined with one another, insofar as this makes technical sense, without departing from the scope of the invention.

Claims (10)

Method for drying a fuel cell system (100), in particular a fuel cell stack (101) of the fuel cell system (100), in particular when the fuel cell is switched off, at a standstill, in standby mode and/or in start-stop mode lensystems (100), preferably in preparation for a start, in particular a freeze start, of the fuel cell system (100), comprising: - shutting off a cathode path (K) of the fuel cell system (100), - initiating a recirculation operation (opZ) in the cathode path (K) , in particular through a bypass line (13) of a cathode system (10), - homogenization and inerting of a cathode gas enclosed in the cathode path (K) by the recirculation mode (opZ). procedure after claim 1 , characterized in that the method has at least one further step: - conducting the cathode gas enclosed in the cathode path (K) through a desiccant (TM) in the cathode path (K). procedure after claim 1 or 2 , characterized in that the method comprises at least one further step: - recirculating an anode gas enclosed in the anode path (A). Method according to one of the preceding claims, characterized in that when the method is carried out, a specific, in particular falling, pressure difference is set between an anode space and a cathode space of the fuel cell system (100). Method according to one of the preceding claims, characterized in that the method has at least one further step: - Operating a cooling system of the fuel cell system (100). Method according to one of the preceding claims, characterized in that the method has at least one further step: - Carrying out a regeneration operation of a desiccant (TM) in the cathode path (K), in particular via a bypass line (13), preferably for dehumidifying the desiccant (TM). Method according to one of the preceding claims, characterized in that before carrying out the method, in particular before shutting off a cathode path (K) of the fuel cell system (100), at least one step is carried out: - blowing out the cathode path (K) of the fuel cell system (100) , Fuel cell system (100) comprising: at least one fuel cell stack (101), a cathode system (10) for providing a cathode gas to the fuel cell stack (101), wherein the cathode system (10) is designed with a path capable of recirculation, which is formed in particular with the aid of a bypass line (13) to a cathode path (K) through the fuel cell stack (101), and a control unit (102) for controlling the fuel cell system (100), wherein the control unit (102) is designed to carry out a method according to one of the preceding claims. Fuel cell system (100) according to the preceding claim, characterized in that a desiccant (TM) is provided in the cathode system (10), in particular in the bypass line (13) to the cathode path (K), wherein in particular: - the desiccant ( TM) is integrated in the bypass line (13), - the desiccant (TM) has a water-absorbing material, e.g. Has pipe insert, and / or - the desiccant (TM) has at least one, in particular grid-like and / or sieve-like injector. Fuel cell system (100) after claim 8 or 9 , characterized in that a heater (HT) in the cathode system (10), in particular in the bypass line (13) to the cathode path (K), preferably parallel to a drying agent (TM), is provided.

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