阅读说明：本技术 用于释放燃料电池系统的方法以及燃料电池系统 (Method for releasing a fuel cell system and fuel cell system ) 是由 A·佩尔格 C·德特马 于 2018-12-06 设计创作，主要内容包括：本发明涉及一种用于释放燃料电池系统的方法以及一种燃料电池系统。该方法包括下述步骤：i)检测压力值(P<Sub>MD</Sub>),其指示阳极子系统的一个区段(MD)内的压力,该区段(MD)开始于减压器(224)的下游；ii)如果所述压力值(P<Sub>MD</Sub>)大于压力极限值(P<Sub>TAVc</Sub>)且存在释放请求,则在泄压时间间隔(t<Sub>DE</Sub>)中使区段(MD)进行泄压；然后iii)如果所述区段(MD)中的压力值(P<Sub>MD</Sub>)在泄压之后小于压力极限值(P<Sub>TAVc</Sub>),则释放燃料电池系统。(The invention relates to a method for releasing a fuel cell system and to a fuel cell system. The method comprises the following steps: i) detecting a pressure value (P) MD ) Indicating the pressure within a section (MD) of the anode sub-system, which section (MD) starts downstream of the pressure reducer (224); ii) if said pressure value (P) is not reached MD ) Greater than the pressure limit value (P) TAVc ) And there is a release request, then in the release time interval (t) DE ) Venting the section (MD); then iii) if the pressure value (P) in said section (MD) MD ) At the pressure reliefThen less than the pressure limit value (P) TAVc ) The fuel cell system is released.)

1. Method for releasing a fuel cell system, the method comprising the steps of:

-detecting a pressure value (P)_MD) -said pressure value being indicative of the pressure within a section (MD) of the anode sub-system, which section (MD) starts downstream of the pressure reducer (224);

-if said pressure value (P) is not present_MD) Greater than the pressure limit value (P)_TAVc) And if there is a release request, the section (MD) is depressurized; then the

-if the pressure value (P) in said section (MD) is_MD) Less than a pressure limit (P) after pressure relief_TAVc) The fuel cell system is released.

2. A method according to claim 1, wherein the pressure relief is performed by letting fuel flow from said section (MD) directly or indirectly into an anode (a) of a fuel cell stack (300) of a fuel cell system.

3. A method according to claim 1 or 2, wherein the pressure relief is performed by letting fuel flow from said section (MD) directly or indirectly into an exhaust system (416) of the fuel cell system.

4. Method according to any of the preceding claims, wherein before the pressure relief and after the release request it is checked whether a possible tank shut-off valve (210) upstream of the pressure reducer (224) is closed and the section (MD) is only subjected to pressure relief when the possible tank shut-off valve (210) is closed.

5. Method according to any of the preceding claims, wherein the fuel discharged during pressure relief is catalytically converted on the catalyst surface (K).

6. The method according to any of the preceding claims, wherein the fuel cell system operates the oxidant conveyor (410) such that the fuel is diluted before it leaves the fuel cell system.

7. Method according to any one of the preceding claims, wherein if the pressure value (P) in said section (MD) is greater than a predetermined value_MD) After the pressure relief is less than a maximum operating pressure limit (Pmax) that is allowed to occur during operation of the fuel cell system for providing power, the fuel cell system is released.

8. Method according to any one of the preceding claims, wherein if the detected pressure value is less than a pressure limit value (P)_TAVc) Then, no pressure relief is performed and the pressure value (P) is detected_MD) After which release has taken place.

9. A fuel cell system having at least one controller, wherein the controller is configured to:

-detecting a pressure value (P)_MD) -said pressure value being indicative of the pressure within a section (MD) of the anode sub-system, which section (MD) starts downstream of the pressure reducer (224);

-if said pressure value (P) is not present_MD) Greater than the pressure limit value (P)_TAVc) And there is a release request, then venting the section (MD); and is

-if the pressure value (P) in said section (MD) is_MD) Less than a pressure limit (P) after pressure relief_TAVc) Then the fuel cell system is subsequently released.

10. Motor vehicle comprising a fuel cell system according to claim 9.

Technical Field

The technology disclosed herein relates to a method for releasing a fuel cell system and a fuel cell system configured for implementing the method disclosed herein.

Background

Such a fuel cell vehicle is known. In a fuel cell vehicle, fuel is stored in a pressure vessel under high pressure. Fuel must be supplied to the fuel cell stack during operation in a significantly lower pressure range. The pressure change is effected by means of a so-called pressure regulator or reducer. The region downstream of the pressure regulator is generally referred to as the medium pressure region. Between the pressure reducer and the fuel cell stack, another pressure reducer may be installed, which further reduces the pressure to a low pressure. In order to protect the components in the intermediate pressure region and as a safety measure, the tank shut-off valve is closed and, if necessary, the anode shut-off valve is closed when the upper permissible pressure limit in the intermediate pressure region is exceeded. In addition, an overpressure valve is usually installed in the medium-pressure region, which is triggered when it is further exceeded.

If the motor vehicle is now parked for a longer time, the following may occur: in the medium-pressure region, a pressure value occurs at which the valve is already closed, but the excess-pressure valve has not yet been triggered. This may be caused, for example, by a minimum leakage at the pressure regulator and/or by an increase in the ambient temperature. In this case, the control device of the fuel cell system does not allow the release. In other words, the control device does not allow the vehicle to start on the basis of the pressure in the intermediate pressure region, although there is no fault here. In previously known solutions, the control device is unable to distinguish between a fault and a tolerable pressure rise.

Disclosure of Invention

A preferred task of the technology disclosed herein is to reduce or eliminate at least one of the drawbacks of the previously known solutions or to propose an alternative solution. A preferred object of the technology disclosed herein is, in particular, to provide a method or a motor vehicle in which a fault does not occur in the anode sub-system downstream of the pressure reducer and therefore a tolerable pressure increase does not prevent the motor vehicle from starting. Other preferred tasks may result from advantageous effects of the techniques disclosed herein. The one or more tasks are solved by the solution of the independent patent claims. The dependent claims are preferred embodiments.

The object is achieved, inter alia, by a method for releasing a fuel cell system and a fuel cell system designed for carrying out one of the methods disclosed herein.

The technology disclosed herein relates to a fuel cell system having at least one fuel cell. Fuel cell systems are conceivable, for example, for mobile transport applications, such as motor vehicles (e.g., passenger cars, motorcycles, commercial vehicles), in particular for supplying at least one drive machine with energy for driving the motor vehicle forward. In its simplest form, a fuel cell is an electrochemical energy converter, which converts a fuel and an oxidant into reactive products and generates electrical energy and heat there. A fuel cell comprises an anode and a cathode separated by an ion-selective or ion-permeable separator. The anode is supplied with fuel. Preferred fuels are: hydrogen, low molecular weight alcohols, biofuels or liquefied natural gas. The cathode is supplied with an oxidant. Preferred oxidizing agents are, for example, air, oxygen and peroxides. The ion-selective separator can be configured, for example, as a Proton Exchange Membrane (PEM). Preferably, a cation selective polymer electrolyte membrane is used. Materials for such membranes are for example: andtypically a plurality of fuel cells are combined into a fuel cell stack or stack.

The fuel cell system includes an anode sub-system formed by fuel-directing components of the fuel cell system. The anode subsystem may have at least one pressure vessel, at least one fuel tank shut-off valve, at least one pressure reducer, at least one anode inflow path leading to an anode inlet of the fuel cell stack, an anode chamber in the fuel cell stack, at least one recirculation flow path leading away from an anode outlet of the fuel cell stack, at least one water separator, at least one anode purge valve, at least one active or passive fuel recirculation conveyor, and other elements. The main task of the anode subsystem is to introduce and distribute fuel to the electrochemically active surface of the anode chamber and to exhaust the anode exhaust gas. The fuel cell system includes a cathode subsystem. The cathode subsystem is formed by components that direct the oxidant. The cathode subsystem may have at least one oxidant conveyor, at least one cathode inflow path leading to a cathode inlet, at least one cathode exhaust path leading away from a cathode outlet, a cathode compartment in the fuel cell stack, and other components. The main task of the cathode subsystem is to introduce and distribute the oxidant over the electrochemically active surface of the cathode chamber and to drain the unused oxidant.

The technology disclosed herein also includes at least one stress-reducer. A pressure reducer is disposed downstream of the at least one pressure vessel and upstream of the at least one fuel cell in the anode sub-system. The pressure reducer is configured to reduce a fuel inlet pressure present at the inlet of the pressure reducer to a fuel outlet pressure or back pressure present at the outlet of the pressure reducer. The pressure reducer may in its simplest form be a throttle valve. Usually, the pressure reducer comprises a pressure reducing valve, which ensures that a certain outlet pressure is not exceeded on the outlet side even at different inlet pressures. The fuel expands in the pressure reducer. Preferably a first pressure reducer is used and a second or further pressure reducer is used downstream.

In one embodiment of the presently disclosed technology, the releasing of the fuel cell system may include the steps of: after the release, the fuel cell system can be switched from an inactive state (i.e. non-use phase), in which it does not supply energy to possible electrical consumers, into an active operating state, in which it can supply electrical energy to possible external electrical consumers. In a preferred embodiment, it is provided that the fuel tank shut-off valve disclosed herein cannot be actuated in the unreleased state of the fuel cell system until the fuel cell system is released. The tank shutoff valve cannot be opened any more in the locked state. Here, there is no mechanical locking of the tank shut-off valve, but all other signals that it is desired to open the tank shut-off valve are covered until they are released. In other words, the tank shut-off valve can only be opened if there is a release.

The release request is a direct or indirect request for releasing the fuel cell system, for example, if a user wants to start the fuel cell system or the fuel cell vehicle. Such a request may also be made indirectly. For example, it can be provided that the unlocking of the vehicle door has already been evaluated as a request for releasing the fuel cell system. Such a release request may initiate a start-up procedure of the fuel cell system.

Suitably, the method disclosed herein comprises the steps of: a pressure value is detected that is indicative of a pressure within a segment of the anode sub-system that begins downstream of the pressure reducer.

The segment typically terminates upstream of the at least one fuel cell or upstream of the fuel cell stack of the fuel cell system. Usually, a further or second pressure reducer is provided between the aforementioned first pressure reducer and the at least one fuel cell. In one embodiment, the section has an intermediate pressure level which is lower than the pressure level upstream of the first pressure reducer and higher than the pressure level downstream of the second pressure reducer. In such embodiments, the section may also be referred to as a medium pressure region. It is also conceivable to use only one pressure reducer.

The pressure value indicates the pressure within the zone. In one embodiment, the pressure value can be directly the signal of a pressure sensor arranged in the section. In another embodiment, the pressure value may be determined indirectly, for example, by sensing other parameters.

Suitably, the pressure value is determined according to the techniques disclosed herein during an inactive phase of the fuel cell system during which the fuel cell system does not provide power to the electrical consumer. The pressure value is detected in particular when a tank shut-off valve of the pressure vessel system is closed. Further, it is desirable that fuel is not extracted from the fuel cell system or the section when the pressure value is detected. It is desirable that the anode shut-off valve upstream of the fuel cell stack in the anode inflow path has been closed during the detection of the pressure value.

The technology disclosed herein further comprises the steps of: if the pressure value is greater than the pressure limit and there is a release request, the segment is vented.

Depressurization comprises processes defined herein that cause a pressure drop when the fuel cell system is not damaged or is subject to tolerable damage.

The pressure relief is preferably carried out for the duration of the pressure relief time interval. The pressure relief time interval is a defined period of time or a defined duration. The pressure relief time interval is typically constant and may be, for example, 5 seconds or 10 seconds or 30 seconds or 1 minute. The pressure relief time interval is preferably chosen to be as short as possible so that the fuel cell system can be started up as quickly as possible. The pressure relief time interval is suitably so long that pressure relief can be achieved in any case if there is no damage to the fuel cell system. The time interval for the pressure release depends inter alia on the way of the pressure release. But this need not be done. It is likewise conceivable for the control device to continuously compare the pressure value with the pressure limit value.

The pressure limit value here indicates the limit pressure in the section disclosed herein.

The limiting pressure is a pressure above the normal operating pressure of the segment. The normal operating pressure of the section is the pressure which prevails during normal or active operation (i.e. operation with energy supply) of the fuel cell system or during inactive phases (e.g. during a night stop).

In a preferred embodiment, a pressure from which the tank shut-off valve is not released (i.e. locked) independently of the operating state of the fuel cell system is selected as the limit pressure. Such pressure limit values and such a locking function are generally provided in order to prevent the fuel cell system from further operating in the event of a fault.

If the pressure value is above the pressure limit value before the pressure relief disclosed herein, it is checked according to the technique disclosed herein whether the pressure increase that may occur in this section during the inactive phase of the fuel cell system is tolerable. However, if the pressure value is below the pressure limit value, there is no critical pressure increase and thus a release can be permitted. The methods disclosed herein may comprise the steps of: if the detected pressure value is less than the pressure limit value, no pressure relief is performed and the release is already performed after the detection of the pressure value. If this is the case, no significant pressure rise occurs during the inactive phase.

The method disclosed herein comprises the steps of: if the pressure value in the section is less than the pressure limit value after the pressure relief, the start-up of the fuel cell system is released. The release can in particular comprise the following steps: releasing the at least one fuel tank shut-off valve. After the release, the at least one fuel tank shut-off valve may be opened to activate the fuel cell system. The methods disclosed herein may further comprise the steps of: releasing the fuel cell system if the pressure value in said section after pressure relief is less than a maximum operating pressure limit value allowed to occur during active operation of the fuel cell system for providing energy. In some cases, a value lower than the limit pressure at which the tank shutoff valve locks up may be selected as the limit value.

The methods disclosed herein may comprise the steps of: before the venting and after the release request, it is checked whether a possible tank shut-off valve upstream of the pressure reducer, i.e. one or all (if there are a plurality of) tank shut-off valves, is closed, and the section is vented only if the possible tank shut-off valve has been closed. It is thus advantageously ensured that fuel does not flow out unhindered in the event of a failure of the pressure reducer.

Pressure relief can be achieved in different ways. In one embodiment, a drain valve is fluidly connected to a section disclosed herein. Through which fuel can escape to the environment. According to the techniques disclosed herein, pressure relief may be provided by flowing fuel from the segment directly or indirectly into the anode of a fuel cell stack of the fuel cell system. For this purpose, the anode shut-off valve of the anode feed line can be opened. Alternatively or additionally, it can be provided that the pressure relief is carried out by the fuel flowing from the section directly or indirectly into an exhaust system of the fuel cell system. The exhaust system may be formed by a cathode exhaust path, for example. According to the techniques disclosed herein, it may be provided that the fuel discharged during pressure relief is catalytically converted on the catalyst surface. For this purpose, it can be provided, for example, that a catalyst surface is installed in the exhaust gas path. In one embodiment, it can be provided that the fuel to be discharged is supplied to the cathode of the fuel cell stack via an exhaust line. In a preferred embodiment, the fuel to be discharged during the pressure relief escapes to the cathode exhaust gas system via an anode purge valve and an anode purge line. Such an anode purge valve and anode purge line are suitable for purging (purge) the anode sub-system to remove water and nitrogen from the sub-system. Preferably, the fuel cell system operates the oxidant conveyor at least during the pressure relief such that the fuel to be discharged during the pressure relief is diluted by the ambient air conveyed by the oxidant conveyor before the fuel leaves the fuel cell system.

The technology disclosed herein also relates to a motor vehicle (e.g., passenger vehicle, motorcycle, commercial vehicle) having the fuel cell system disclosed herein.

All features described in connection with the method shown here should likewise be disclosed as structural features of the fuel cell system or of the at least one controller, which can be configured accordingly.

The system disclosed herein includes at least one controller. The controller is configured to implement the method steps disclosed herein. To this end, the controller can at least partially and preferably completely regulate (closed-loop control) or control (open-loop control) the actuators of the system on the basis of the signals provided. The controller may affect at least the cooling system of the fuel cell system, in particular the cathode subsystem, the anode subsystem and/or the fuel cell system. Alternatively or additionally, the controller may also be integrated in another controller, such as a higher-level controller. The controller may interact with other controllers of the vehicle.

The pressure vessel may be, for example, a high-pressure gas vessel (CGH 2). The high-pressure gas container is designed to store fuel at ambient temperature continuously at a nominal operating pressure (NWP) of about 350 bar (overpressure relative to atmospheric pressure), more preferably about 700bar or more. The cryogenic pressure vessel is adapted to store fuel at the operating pressure described above at a temperature well below the operating temperature of the vehicle.

The technology disclosed herein also relates to a fuel tank shutoff valve. A tank shut-off valve is a valve whose inlet pressure is (substantially) equal to the reservoir pressure. The tank shut-off valve is in particular a controllable or adjustable and in particular a currentless normally closed valve. Tank shut-off valves are usually integrated into on-tank valves (═ OTVs). The on-tank valve is a valve unit mounted directly at one end of the pressure vessel and in direct fluid connection with the interior of the pressure vessel. In commission regulation (EU) for executing regulation (EG)79/2009 of european parliament and council regarding approval of hydrogen-powered vehicle model, No. 406/2010 on 26 th 4/2010, this fuel tank cut-off valve is also referred to as a first valve.

In other words, the technology disclosed herein relates to a fuel cell system and a method for starting up the fuel cell system.

In one embodiment of the technology disclosed herein, the at least one fuel cell of the fuel cell system is designed to briefly reduce the pressure in the medium-pressure region above a pressure limit value to a pressure within a normal range (below the pressure limit value). However, if the "normal" actuation is followed and the tank shut-off valve is then opened, it may not be possible to detect whether the overpressure valve has triggered and has the fuel escape uncontrollably in the event of a malfunction (e.g. a leak in the pressure regulator or a faulty regulation). Such a malfunction may cause the safety function to function and necessitate shutdown of the fuel cell system (emergency shutdown).

If the pressure in the intermediate pressure region is above the pressure limit, the system may be activated according to the techniques disclosed herein as follows:

first, the tank shut-off valve remains closed (safety state).

Then, the at least one fuel cell reduces the pressure in the medium-pressure region (section) until the pressure is within the normal range.

Advantageously, the at least one fuel cell is depressurized in case the fuel cell has not yet provided electrical energy to the consumer (i.e. the fuel cell has not yet started). To vent the medium pressure region, fuel is preferably withdrawn from this section and supplied to the remaining anode subsystem of the feed cell system or to the exhaust line. For this purpose, for example, small amounts of a few milligrams of fuel (the amount depending on the line volume) can be discharged into the anode of the fuel cell stack or directly into the exhaust line via a bypass until the pressure has dropped to a pressure which is allowed for normal operation of the fuel cell system. If the fuel is discharged into the exhaust gas line, the oxidant conveyor may supply ambient air to reduce the fuel concentration in the exhaust gas line.

If the pressure in the intermediate-pressure region drops to a value below the pressure limit value or if the pressure value is within a normal range after the intermediate-pressure region has been relieved, a normal starting process of the fuel cell can be started and the tank shut-off valve can be opened or released.

If there is a fault, the pressure in the intermediate pressure region does not drop and a shut-off point defined for operation takes effect and the tank shut-off valve closes when the permissible pressure value in the intermediate pressure region is exceeded.

It is advantageously possible to precisely detect pressure values which are above those permitted for normal operation (i.e. outside the normal range) and the triggering of the excess pressure valve and thus faults in the system and to take safety measures. Furthermore, progressive faults may also be identified. The usability of the motor vehicle can be advantageously increased.

If there is a fault at the transition from the high pressure region to the medium pressure region (i.e. at the pressure reducer), the medium pressure cannot be reduced significantly by the pressure relief disclosed herein. The small amount of discharged hydrogen is not sufficient to sufficiently lower the pressure because the fuel is continuously flown from the high-pressure region. The fault is recognized before opening the tank shutoff valve and the tank shutoff valve is not opened. So that only a relatively small amount of fuel flows out.

Further, the technology disclosed herein relates to a method for checking the tightness of an anode sub-system segment downstream of a pressure reducer, wherein a pressure value indicative of the pressure of the segment is detected at time intervals during an inactive phase of the fuel cell system. The pressure change is determined from the values detected at time intervals and used as a measure of the tightness. The method may comprise the steps of: the change of the ambient temperature is detected simultaneously with the detected pressure value, and the change of the pressure value related to the temperature is taken into consideration when detecting the sealability. In other words, it may be checked regularly whether the tightness requirements of the system are met. Progressive deterioration of the system can be identified by the parameter "pressure rise during parking" (taking into account the temperature in the system during parking). Thus, measures (such as maintenance) can be taken in time before a failure occurs in operation.

Drawings

The technology disclosed herein is now explained with reference to the drawings. The attached drawings are as follows:

FIG. 1 shows a schematic diagram of a fuel cell system;

fig. 2 shows highly schematically the pressure values P_MDTime profile of (d); and

fig. 3 schematically illustrates one embodiment of the method steps disclosed herein.

Detailed Description

The fuel cell system disclosed herein is schematically illustrated in fig. 1, fuel, such as hydrogen, is stored in pressure vessel 200 at a pressure of 700bar, pressure vessel 200 provides hydrogen for fuel cell stack 300 having a plurality of fuel cells which operate at a lower pressure level, such as 0.5 to 1bar ü (for an overpressure compared to atmospheric pressure), tank shutoff valve 210 is provided at one end of pressure vessel 200, instead of only one pressure vessel 200 having tank shutoff valve 210, a plurality of pressure vessels 200 having a plurality of tank shutoff valves 210 are provided, furthermore, in the system illustrated herein, two pressure stages are provided which are operated by one pressure 222, 224, respectively, a first pressure stage reduces the pressure from 700bar to a medium pressure level (medium pressure range), such as 10 to 20bar or 13 to 16bar, a second pressure stage reduces the pressure from the medium pressure level to a low pressure of the fuel cell, a second pressure stage is provided downstream of fuel cell stack from the medium pressure level to a low pressure level, which may be purged downstream of fuel cell stack by a fuel cell stack pressure regulator 430, a second pressure reducer is provided downstream of a fuel cell dilution line 430, a second pressure reducer, a fuel cell dilution line, a pressure regulator, a second pressure reducer, a fuel cell line, a pressure reducer, a pressure regulator, a second pressure reducer, a pressure regulator, a line, a pressure regulator, a line, a pressure regulator, and a pressure regulator, a pressure reducer, a pressure regulator, a line, a pressure regulator, a line, a pressure regulator, a line, a pressure regulator.

Fig. 2 shows highly schematically the pressure values P_MDThe pressure in this section MD is used as the pressure value. The fuel cell system is stopped at time t0 (Parken). The pressure is constantly increasing due to the intensive heating of the fuel cell system during the inactive phase. At time t1, the pressure in section MD reaches a limit pressure or pressure limit value P_TAVc. From this point on, the tank shutoff valve 210 is locked for safety for all other functions. The fuel tank shut-off valve can now only be opened again after the release has taken place. The pressure in the section MD rises further until the triggering pressure P of the overpressure valve arranged in the section MD is reached at the time t2_PRVo. The overpressure valve opens and the pressure in the section MD drops until the pressure drops at time t3 to the closing pressure P of the overpressure valve_PRVc. After closing, the pressure in the section MD rises again on continued heating until the trigger pressure P_PRVo(time t4) and then falls off againPressure P_PRVc(time t 5). The pressure does not drop to a pressure below the limit pressure of the tank shut-off valve. Therefore, if the technology disclosed herein is not used, the tank cut-off valve is always locked during the start-up. Now, at time t6, a release request is issued, for example because the user wants to start the vehicle. At this point the method steps according to fig. 3 begin.

One embodiment of the method steps disclosed herein is schematically illustrated in fig. 3. The method disclosed herein begins with step S100. In step S200, a pressure value P in a zone may be detected_MD。

The detected pressure value P may be determined in step S300_MDWhether the pressure in this case in the section MD is greater than the triggering pressure P of the pressure reducer 224_PRVo. If this is the case, the fuel cell system or the tank shut-off valve 210 locks or remains locked and a corresponding warning is issued to the user and/or a third party (for example, to the control room by telemetry) (see step 730). But this need not be done.

But if a pressure value P is detected_MDNot greater than the trigger pressure P_PRVoThen the detected pressure value P may be determined in step S400_MDWhether or not it is greater than pressure limit value P of fuel tank cut-off valve 210_TAVc. If this is not the case, a release may be performed (see step S710). But if a pressure value P is detected_MDAbove a pressure limit value P_TAVcThe pressure is not desirably reduced by pressure relief during the inactive phase of the fuel cell system. Where it rises even significantly (see figure 2). In this case (i.e. P)_TAVc＜P_MD＜P_PRVo) First, in step S510, it is checked whether the tank cut valve 210 is closed. If this is the case, in step S520, i.e. in the pressure relief time interval t_DE(see fig. 2) the section MD is vented. This may be done, for example, by opening anode purge valve 238. Preferably, the fuel cell system does not provide electrical power to other electrical consumers. The fuel passes through an anode purge valve 238 to a cathode exhaust gas line 416 where the fuel is diluted with ambient air (see fig. 1). However, other arrangements for pressure relief are also conceivable. For example, a bypass may branch off from section MD and lead into cathode exhaust line 416. During the pressure relief, processes are carried out which, in the absence of a fault, cause a pressure value P in the section MD_MDIs reduced. However, if a fault, such as a fault in the pressure reducer 224, is present, which for example leads to a pressure increase in the inactive phase, then in the pressure relief time interval t_DEThe medium pressure value also continues to rise (see dashed line in fig. 2). It is determined in step S600 that the pressure is released (here: at a pressure release time interval t)_DEThereafter) at time t6_MDWhether or not less than the pressure limit value P_TAVc。

If this is the case, a release may be performed (see step S710). In this case, the pressure rise of the fuel cell system during the inactive phase can be attributed to environmental influences and/or negligible leaks, which are not critical for the operation of the fuel cell system. Nevertheless, an indication may be issued if necessary. But if a pressure value P is detected_MDAbove a pressure limit value P_TAVcThen a fault may exist. In step 720, the fuel cell system or the tank shut-off valve 210 is thus locked or remains locked and a corresponding warning is issued to the user and/or a third party (for example, by telemetry to the control room) (see step 720).

The foregoing description of the invention is for the purpose of illustration only and is not intended to be limiting of the invention. Within the scope of the present invention, various improvements and modifications may be made without departing from the scope of the present invention and its technical equivalents.

List of reference numerals

300 fuel cell stack

A Anode Chamber

200 pressure vessel

210 fuel tank shut-off valve

215 anode inflow path

216 recirculation flow path

222 second pressure reducer

224 first pressure reducer

232 water separator

238 anode purge valve

234 recirculation jet pump

236 circulating conveyer

239 anode purging pipeline

MD section

ND Low Voltage section

K cathode chamber

410 oxidant conveyer

415 cathode inflow path

420 heat exchanger

430 supply-stack stop valve

440 waste gas stack stop valve

416 cathode exhaust gas path

460 fuel cell bypass