Method and apparatus for operating a fuel cell system

Abstract

The present invention relates to a method for operating a fuel cell system (10) having at least one fuel cell stack (100) with an air side (120) and a fuel side (130). The fuel cell system (10) operates under different operating conditions, including a normal operating condition (BS350) for outputting electricity and a plurality of special operating conditions during transition from or to the normal operating condition (BS350). The method includes detecting the current operating condition of the fuel cell system (10) and regulating the fuel cell system (10) according to the detected current operating condition. For the detected special operating condition, the air temperature that can be supplied to the fuel cell system (10) through the air inlet section (112) is regulated by at least one electric heater (223, 243). Furthermore, according to the special operating condition, the direction of at least one flow path of the heated air within the fuel cell system (10) is selected from at least two possible flow path directions of the fuel cell system (10). The present invention also relates to a computer program product and a control device (20) for performing the method. The present invention also relates to a fuel cell system (10).

Description

Technical Field

[0001] This invention relates to a method for operating a fuel cell system, as well as a computer program product and control device for performing the method. The invention also relates to a fuel cell system. Background Technology

[0002] Fuel cells are an ideal solution for generating electricity from energy carriers such as natural gas or biomethane while avoiding emissions. To this end, natural gas or biomethane can be converted into hydrogen in a reformer to supply the fuel cell. In a fuel cell, the electrochemical reaction of hydrogen and oxygen produces only electricity, water, and heat, without generating harmful emissions such as carbon dioxide.

[0003] Solid oxide fuel cells (abbreviated as SOFC in English) have proven particularly advantageous in this respect, as they can operate very efficiently in a temperature range of 500°C to 900°C.

[0004] As is known from existing technology, fuel cell systems operate under different operating conditions, such as standby or active operation. Because high-temperature electrolysis requires high temperatures, the intermediate state between standby and active operation presents unique technical challenges to the operating strategies used to control the fuel cell system. For example, the start-up and shutdown processes must take temperature-sensitive components into account, and equipment safety must be ensured.

[0005] The drawbacks of existing operating strategies include the relatively long duration and high energy consumption of the start-up and shutdown processes. During these processes, the components of the fuel cell system are subjected to relatively high thermal and mechanical loads. Furthermore, protective or inert gases are often required during start-up and shutdown to allow the fuel cell system to operate in these transitional states. This results in the need to consider the use of protective gases in the construction and control technology of the fuel cell system. This leads to high complexity in the control software and the fuel cell system itself. Consequently, the design, manufacturing, and operating costs of the fuel cell system increase accordingly. In addition, the use of protective gases incurs additional energy consumption, which may lead to a decrease in the efficiency of the fuel cell system. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to at least partially overcome the above-mentioned disadvantages. In particular, the technical problem to be solved by the present invention is to improve the efficiency of high-temperature fuel cell systems in an economical, efficient, and simple manner. Preferably, the present invention also provides a solution in which the use of protective gas or inert gas can be omitted during the transition state of the fuel cell system operation.

[0007] The aforementioned technical problem is solved by a method having the features of claim 1, a computer program product having the features of claim 13, a control device having the features of claim 14, and a fuel cell system having the features of claim 15.

[0008] Other advantages and features of the invention are derived from the dependent claims, the description, and the drawings. Herein, features and details relating to the method according to the invention also apply to features and details relating to the computer program product according to the invention, the control device according to the invention, and the fuel cell system according to the invention, and vice versa; therefore, cross-reference is always possible with respect to the disclosures relating to various aspects of the invention.

[0009] One aspect of the invention relates to a method for operating a fuel cell system. The fuel cell system has at least one fuel cell stack with an air side and a fuel side. The fuel cell system operates under different operating conditions, including a normal operating condition for outputting electricity, and multiple special operating conditions during transitions to or from the normal operating condition. In this method, the current operating condition of the fuel cell system is detected. The fuel cell system is regulated according to the detected current operating condition. For the detected special operating condition, the air temperature supplied to the fuel cell system through the air inlet portion is regulated at least by an electric heater. Furthermore, for the detected special operating condition, at least one flow path of the heated air within the fuel cell system is selected from at least two possible flow paths of the fuel cell system according to the detected special operating condition.

[0010] In other words, the present invention provides a method for operating a fuel cell system. This method can, for example, implement an operating strategy.

[0011] Here, "system operation" is preferably understood as guiding the system to work. A fuel cell system may be, for example, a high-temperature fuel cell system or a SOFC fuel cell system.

[0012] The fuel cell system has at least one fuel cell stack with an air side and a fuel side, as well as different operating conditions.

[0013] Within the scope of this invention, "operating condition" can be specifically understood as an operating mode or operating condition. An operating condition can be defined by an instantaneous control sequence of the fuel cell system. Operating conditions can also be defined, for example, by physical quantities occurring in the fuel cell system (e.g., actual pressure or actual temperature) and / or by control commands. A fuel cell system can have multiple different operating conditions. Preferably, the fuel cell system can have only one operating condition at any given time.

[0014] According to the present invention, if the detected operating condition deviates from the normal operation of the fuel cell system for power output, the operating condition is classified as a special operating condition.

[0015] Within the scope of this invention, "detecting the current operating condition" can be specifically understood as recording the actual operating condition. Therefore, detection preferably includes, for example, assessing or classifying this information in addition to receiving and / or measuring information belonging to the operating condition. Thus, the operating condition can be determined, for example, from the information received regarding the operating condition. Within the scope of this invention, "special operating condition" can be specifically understood as an operating condition deviating from the normal operation of the fuel cell system. Therefore, a special operating condition can be, for example, a standby condition and / or transitional state of the fuel cell system that occurs before and / or after normal operation. In particular, a special operating condition can be an operating condition during a heating or cooling process. Within the scope of this invention, "normal operation" can be specifically understood as the steady-state or at least partially steady-state operation of the fuel cell system. During normal operation, the fuel cell system converts chemical energy into electrical energy as intended and outputs electrical energy as current. Preferably, normal operation can include the operation of the fuel cell system at full load and / or partial load (preferably at least 50% of its capacity).

[0016] According to the present invention, the fuel cell system is adjusted based on the detected operating conditions.

[0017] Within the scope of this invention, "regulation" is specifically understood as the monitoring and / or control of the inputs, parameters, adjustments, and / or components of a fuel cell system.

[0018] For any detected special operating conditions, the air temperature supplied to the fuel cell system through the air inlet is regulated by at least one electric heater. Furthermore, for any detected special operating conditions, at least one flow path for the electrically heated air in the fuel cell system is selected from at least two possible flow paths based on the detected special operating conditions.

[0019] Within the scope of this invention, "flow path" is specifically understood as the flow route of a fluid (e.g., air or other cathode gas). Preferably, the flow path can extend between two points, and the flow path is preferably part of the route between a source and a sink of flow. Within the scope of this invention, "direction" can be specifically understood as an extension or connection between two points. Within the scope of this invention, "selection of direction" can be specifically understood as the targeted specification and / or adjustment of one of several possible flow paths in a fuel cell system. By selectively selecting the direction, a flow path can be specified for electrically heated air from several possible flow paths in the fuel cell system. For this purpose, the electric heater can be connected to at least two mutually separate flow paths.

[0020] According to the method of the invention, operating conditions that do not correspond to normal operation can be identified and specifically controlled. In operating conditions occurring during the transition to or from normal operation, heating is performed using an electric heater that can rapidly and precisely provide a defined amount of heat. Furthermore, by selecting flow paths, heat can be locally and specifically distributed within the fuel cell system. The combination of these structural features allows for the elimination of the need for protective or inert gases, as portions and / or components of the fuel cell system can be specifically and sequentially heated and cooled. Correspondingly, this method allows heating and cooling processes to be performed using only normally operating equipment. Therefore, energy consumption and operating costs can be reduced without compromising equipment safety.

[0021] According to the preferred configuration, the first heating operating condition for heating the fuel cell system can be detected as one of the special operating conditions transitioning to normal operating conditions. The special operating condition can therefore include the first heating operating condition. The first heating operating condition can precede the normal operating condition. Preferably, after the process requirements for heating the fuel cell system are met, the fuel cell system can operate in the first heating operating condition.

[0022] In the first heating operating condition, the fuel cell system preferably heats the primary electric heater to the heater temperature. Furthermore, the air temperature is preferably regulated by the secondary electric heater during the first heating operating condition. Preferably, the air temperature can be regulated using a catalytic converter heating profile. The flow path of the air heated by the secondary heater can be selected such that the air is directed toward the catalytic converter of the fuel cell system, which is configured to catalytically combust fuel exhaust gases, to heat the catalytic converter to its catalytic converter activation temperature. Operation in the first heating operating condition can preferably continue at least until the catalytic converter reaches its catalytic converter start-up temperature.

[0023] Thus, under the first heating operation condition, the catalyst in the fuel exhaust path can be heated to its catalyst activation temperature by at least one electric heater, which is done by guiding heated air to the catalyst by at least one electric heater.

[0024] Within the scope of this invention, "process requirements" can be specifically understood as programming or control instructions issued by the user (e.g., that can be transmitted to a control device).

[0025] Therefore, the catalyst can be heated to its activation temperature at the start of the heating process. Reaching the activation temperature allows for the supply of additional fuel cells to the fuel cell system without the risk of releasing harmful substances, as the catalyst can be chemically activated. Simultaneously, heat can be generated in the fuel cell system through catalytic combustion and distributed from the catalyst, thereby accelerating and safely carrying out the heating process.

[0026] According to another preferred configuration, a second heating operation condition for heating the fuel cell system can be further detected as one of the special operating conditions for transitioning to normal operation. This special operating condition can precede the normal operation condition, and preferably precedes the first heating operation condition. This special operating condition can be the second heating operation condition. The fuel cell system can operate under the second heating operation condition as long as the catalyst has at least the catalyst start-up temperature for catalytic combustion of fuel exhaust gases in the fuel cell system.

[0027] For the second heating operation, hot gas (e.g., methane) can be supplied to the fuel supply section on the fuel side via the fuel line to supply fuel and receive heat from the heated air within the fuel cell stack. The supplied hot gas can also circulate in the fuel cell system's recirculation line to heat the fuel-guiding line of the fuel cell system. Here, the recirculation line can extend between the fuel exhaust section on the fuel side for discharging fuel exhaust gas and a portion of the fuel line upstream of the fuel supply section. Furthermore, the air temperature can be regulated at least by the primary electric heater. Preferably, temperature regulation can be performed using a fuel line heating profile. Additionally, the flow path of the heated air can be selected, the flow path being from the preferred primary heater towards the air supply section on the air side. Preferably, the fuel cell system can operate under the second heating condition at least until the recirculation line and fuel line have a minimum line temperature. Preferably, the minimum line temperature should be at least the water vapor condensation temperature. Preferably, the water vapor condensation temperature can be limited by the operating pressure within the fuel line.

[0028] Therefore, under the second heating operation condition, the fuel supply line of the fuel cell system can be heated by guiding heated air from at least one electric heater to the air side of the fuel cell stack, and by supplying hot gas from the fuel side to the fuel cell stack to receive heat from the heated air at the fuel cell stack, wherein the heated gas is circulated through a circulation line between the fuel exhaust section and the fuel supply line section.

[0029] Therefore, the fuel line can be heated to a defined temperature. In particular, it prevents the water vapor, which should be supplied to the reformer for reforming, from condensing in the fuel line. Advantageously, the hot gases in the fuel cell stack can receive heat and can be reused for heating via circulation. This allows the heating process to be performed quickly and safely. The hot gases can be, in particular, anode gases, which are also preferably used during normal operation.

[0030] According to a preferred configuration, the fuel cell system can also operate under a third heating operating condition for heating the fuel cell system. This third heating operating condition can precede the normal operating condition and preferably follows the second heating operating condition. The third heating operating condition can be a special operating condition. The third heating operating condition can be detected as one of the special operating conditions for transitioning to the normal operating condition. Preferably, the fuel line and circulation line of the fuel cell system can operate under the third heating operating condition if they have at least a minimum line temperature. Preferably, the minimum line temperature can be the water vapor condensation temperature.

[0031] Preferably, for the third heating operation, the air temperature can be regulated by at least one secondary electric heater. Preferably, the flow path of the air heated by the secondary heater can be selected from the heater towards the inlet of the reformer heat exchanger to heat the reformer to its reformer activation temperature. The reformer can be located in the fuel cell system to generate fuel to be supplied from the fuel side. Alternatively or supplementarily, the flow path can also be selected from the heater towards the catalyst of the fuel cell system for catalytic combustion of fuel exhaust gases. Furthermore, the temperature of the reformer can be regulated to the reformer start-up temperature, such as its reformer activation temperature, which is preferably achieved by regulating the flow rate of the heated air through the reformer heat exchanger via a control valve. The control valve can be located upstream of the inlet of the reformer heat exchanger along the flow path. Therefore, the reformer temperature is preferably regulated according to the reformer heating profile. Once the reformer reaches its start-up temperature, steam can be supplied to it.

[0032] Therefore, under the third heating operation condition, the reformer can be heated to its activation temperature for fuel production by guiding the heated air from at least one electric heater to the reformer heat exchanger.

[0033] The reformer can be heated to its activation temperature. A rapid heating time is possible because heat from the (secondary) heater and fuel cell stack can be used. Simple and precise temperature control is achieved through regulation of the reformer temperature via control valves. The addition of water vapor when the reformer's activation temperature is reached prevents carbon buildup on the reformer catalyst surface. Therefore, the heating process can be implemented quickly and safely.

[0034] According to a preferred configuration, the fuel cell system can further operate under a fourth heating operating condition. This fourth heating operating condition can precede the normal operating condition and preferably follows the third heating operating condition. Therefore, the fourth heating operating condition can be a specific operating condition. The fourth heating operating condition can be detected as one of the specific operating conditions for transitioning to the normal operating condition. Preferably, operation under the fourth heating operating condition is possible if the reformer of the fuel cell system used to generate fuel to be supplied to the fuel side has at least a reformer start-up temperature, such as a reformer activation temperature.

[0035] For the fourth heating operation condition, the air temperature is preferably regulated by a primary electric heater and / or a secondary electric heater until the fuel cell stack reaches its minimum stack temperature. The flow path of the air heated by the heaters (or multiple heaters) can be selected to be a portion of the pipeline connected to the air supply path that guides the air to the air side via heat transfer or by fluid technology. Furthermore, steam and hot gases can be supplied to the reformer to produce fuel. Additionally, the resulting fuel and heated air can be supplied to the fuel cell stack.

[0036] Therefore, in the fourth heating operation condition, the fuel cell stack can be heated to the minimum stack temperature by guiding the air heated by the electric heater to the air side, and water vapor and hot gas can be supplied to the reformer for fuel production, wherein the produced fuel is supplied to the fuel side to release the heat in the fuel cell stack by generating electricity.

[0037] In this way, syngas can be generated in the reformer as reformed gas. This syngas, along with heated air, can be used to additionally heat the fuel cell stack. The air can be heated electrically and indirectly through the catalytic combustion of the syngas in the catalyst.

[0038] For example, the fuel cell system can also operate in a ready-to-operate condition. The ready-to-operate condition can precede the normal operating condition and preferably follows a fourth heating operating condition. Preferably, the ready-to-operate condition can be detected as a special operating condition or another normal operating condition. Preferably, the ready-to-operate condition is used for operation when the fuel cell stack temperature has at least a minimum stack temperature. For the ready-to-operate condition, steam and hot gas can be supplied to the reformer to produce fuel. Furthermore, the fuel thus produced, as well as electrically heated or catalytically heated air, can be supplied to the fuel cell stack. Additionally, the flow rates of heated air and fuel to the fuel cell stack can be regulated to a minimum, wherein the fuel cell stack has at least a minimum stack temperature.

[0039] Therefore, the fuel cell system can be kept in a ready-to-operate state, for example, it can transition from a ready-to-operate state to normal operation as active operation. The resources required to maintain this state can be reduced to the bare minimum necessary.

[0040] According to the preferred configuration, the fuel cell system can operate under normal operating conditions corresponding to normal operation, preferably when the fuel cell stack has at least a minimum stack temperature. Preferably, the normal operating conditions can follow the low-power operating conditions. The normal operating conditions can be detected.

[0041] Under normal operating conditions, air and fuel can be supplied to the fuel cell stack. Electric current can be generated within the fuel cell stack using the supplied air and fuel. The temperature of the fuel cell stack can be controlled by catalytic heating. Correspondingly, at least one electric heater can preferably be deactivated. Catalytic heating can be achieved, for example, by guiding exhaust gas from the air outlet portion on the air side and fuel exhaust gas from the fuel exhaust portion on the fuel side to the catalyst of the fuel cell system. The heat of the fuel exhaust gas can be transferred to the fuel to be supplied via at least one fuel heat exchanger. Preferably, the fuel heat exchanger can be arranged in the fuel line portion upstream of the fuel cell stack. The fuel exhaust gas can be catalytically combusted by the catalyst. The heat of the resulting catalyst exhaust gas flow can be transferred to the air to be supplied via at least one air heat exchanger. Preferably, the air heat exchanger can be arranged in the air supply path portion upstream of the fuel cell stack.

[0042] Therefore, under normal operating conditions, at least one electric heater can be deactivated, and the temperature of the fuel cell stack can be regulated by transferring the heat of the exhaust gas from the catalyst arranged in the fuel exhaust gas path to the air and fuel to be supplied through a heat exchanger.

[0043] Within the scope of this invention, "catalytic heating" can be specifically understood as the generation of heat within the catalyst and the transfer of heat to the fuel cell system. "Electric heater deactivation" can be specifically understood as the interruption of the power supply to the electric heater.

[0044] Therefore, through the active operation of the fuel cell system, the chemical energy in the fuel cell stack can be converted into electrical energy and released to the outside as required.

[0045] The fuel cell system can also have a low-power operating condition. This low-power operating condition can preferably precede or follow the normal operating condition. Alternatively or supplementarily, the low-power operating condition can follow the preparation operating condition or the normal operating condition. For example, a low-power operating condition can be used when processes requiring the generation and release of electricity are in progress. In this low-power operating condition, the generated fuel and heated air can be supplied to the fuel cell stack. Within the fuel cell stack, an electric current can be generated from the supplied air and fuel. The flow rates of the heated air and fuel to the fuel cell stack can preferably be adjusted according to the stack power output curve.

[0046] Therefore, fuel cell systems can be activated by considering the entry or exit of the heat absorption zone.

[0047] According to a preferred configuration, the fuel cell system can further operate under a first cooling operating condition to cool the fuel cell system. Preferably, the first cooling operating condition can follow the normal operating condition, and more preferably, follow the low-power operating condition. Preferably, the first cooling operating condition can be detected as one of the special operating conditions transitioning from the normal operating condition. The fuel cell system can operate under the first cooling operating condition when the process of cooling the fuel cell system is required.

[0048] In the first cooling operation condition, the air temperature can preferably be controlled by at least one electric heater according to a cooling profile. Preferably, the electric heater can be a secondary electric heater of two electric heaters. Furthermore, the flow path of the heated air towards the inlet of the reformer heat exchanger can be selected. The reformer heat exchanger is preferably a reformer of a fuel cell system, provided for generating fuel to be supplied to the fuel side. Additionally, exhaust gas can be supplied from the air side to the inlet of the reformer heat exchanger. The temperature of the reformer can be controlled by regulating the flow rate of a gas mixture comprising heated air and exhaust gas through the reformer heat exchanger using a control valve. The control valve can be located upstream of the inlet of the reformer heat exchanger along the flow path. Preferably, the temperature of the reformer can be controlled according to a reformer cooling profile. The temperature of the fuel cell stack can also be controlled to a first cooling temperature. Preferably, this can be done according to a stack cooling profile. Furthermore, the first cooling temperature can preferably be lower than the minimum stack temperature required for normal operation. To control the temperature of the fuel cell stack, the flow rate of fuel to be supplied to the fuel side can be adjusted. Preferably, the first cooling operation can continue until the first stack cooling temperature is reached. The fuel is preferably fuel produced in the reformer. Preferably, the first cooling temperature can be 377°C.

[0049] Therefore, under the first cooling operating condition, the temperature of the reformer can be regulated by at least one electric heater for fuel production, which is done by supplying heated air to the inlet of the reformer heat exchanger and, in addition, supplying exhaust gas from the air side to the inlet of the reformer heat exchanger.

[0050] In this way, the fuel cell stack can be cooled by the reformate from the reformer. This prevents excessively rapid or strong cooling of the reformer temperature due to heat transfer from the exhaust gas and electrically heated air to the reformer. Here, the control valve enables rapid and efficient control.

[0051] According to another preferred embodiment, the fuel cell system can further operate under a second cooling operating condition to cool the fuel cell system. The second cooling operating condition can follow normal operation and preferably follows the first cooling operating condition. Preferably, the second cooling operating condition can be a special operating condition. Preferably, the second cooling operating condition can be detected as one of the special operating conditions transitioning from normal operation. Preferably, if the fuel cell stack has a first stack cooling temperature, the fuel cell stack can operate under the second cooling operating condition.

[0052] In the second cooling operation condition, the air temperature is preferably regulated by a secondary electric heater. Preferably, the air temperature can be regulated according to a cooling profile. Furthermore, the flow path of the heated air from the electric heater to the catalyst of the fuel cell system used for catalytic combustion of fuel exhaust gases can be selected to enable the catalyst to operate at a temperature above its activation temperature. Additionally, the temperature of the reformer in the fuel cell system, which generates fuel to be supplied to the fuel side, can be regulated to the reformer start-up temperature (e.g., the reformer activation temperature) by supplying hot gas and water vapor to the reformer for heat removal. This can preferably be carried out until the reformer reaches its highest temperature, the reformer start-up temperature. Once the reformer temperature falls below the reformer start-up temperature, the supply of water vapor to the reformer can be interrupted.

[0053] In the second cooling operation condition, the catalyst can be heated by an electric heater to continue operating the catalyst at a temperature higher than its activation temperature. This heating is achieved by supplying heated air to the catalyst from at least one electric heater. Furthermore, the temperature of the reformer can be reduced by supplying hot gas and water vapor to the reformer.

[0054] In this way, the reformer can be cooled below its activation temperature. By interrupting the supply of steam as early as possible, carbon buildup on the catalyst surface of the reformer can be prevented.

[0055] According to a preferred configuration, preferably when the temperature of the reformer used by the fuel cell system to generate fuel to be supplied to the fuel side is below the reformer activation temperature, the fuel cell system can further operate under a third cooling operating condition to cool the fuel cell system. Preferably, the third cooling operating condition can follow the normal operating condition, and more preferably, follow the second cooling operating condition. Preferably, the third cooling operating condition can be a special operating condition. The third cooling operating condition can be detected as one of the special operating conditions transitioning from the normal operating condition.

[0056] Under the third cooling operating condition, the air temperature can preferably be regulated to the catalyst activation temperature via a secondary electric heater. Here, a cooling curve is preferably followed. Furthermore, a flow path can be selected for the heated air from the (secondary) heater towards the catalyst in the fuel cell system for catalytic combustion of fuel. Additionally, by regulating the flow rates of hot gas and air supplied to the fuel supply section on the fuel side, the temperature of the fuel cell stack can be regulated to the second stack cooling temperature. Preferably, the fuel cell system can operate under the third cooling operating condition until the second stack cooling temperature is reached. Preferably, a cooling curve is followed here.

[0057] Therefore, in the third cooling operating condition, the fuel cell stack is preferably cooled to room temperature, wherein the electric heater continues to supply electrically heated air to the catalyst so that the catalyst can operate at a temperature above its activation temperature, and thus maintain the catalytic reaction within the catalyst. The temperature of the fuel cell stack can be controlled by regulating the flow rates of the hot gas and air until the second stack cooling temperature, preferably room temperature, is reached at the fuel cell stack. In this way, the fuel cell stack can be cooled with air and hot gas (e.g., natural gas). Simultaneously, it can be ensured that the catalyst temperature does not fall below its activation temperature, allowing only non-flammable materials to leave the fuel cell system. Therefore, the safety and efficiency of the fuel cell system can be improved.

[0058] According to another preferred configuration, preferably when the temperature of the fuel cell stack is at most the second stack cooling temperature, the fuel cell system can further operate under a fourth cooling operating condition to cool the fuel cell system. Preferably, the second stack cooling temperature is at most room temperature (i.e., 19°C to 22°C). The fourth cooling operating condition can follow the normal operating condition and / or preferably follows the third cooling operating condition. Preferably, the fourth cooling operating condition can be a special operating condition. The fourth cooling operating condition can be detected as one of the special operating conditions transitioning from the normal operating condition.

[0059] For the fourth cooling operating condition, the air temperature can be regulated to the catalyst settling temperature using at least one electric heater (preferably a secondary heater). Preferably, a cooling profile can be followed here. The flow path of the heated air from the heater to the catalyst of the fuel cell system for catalytic combustion of fuel exhaust gases can be selected to cool the catalyst below the catalyst activation temperature. Furthermore, the temperature of the catalyst can be regulated to the catalyst settling temperature, preferably according to the catalyst cooling profile, by adjusting the flow rates of hot gas and air supplied to the fuel supply section on the fuel side. Preferably, the fuel cell system can operate under the fourth cooling operating condition until the catalyst reaches the second stack cooling temperature.

[0060] Therefore, the catalyst can be further cooled, and the fuel cell system can be brought into a safe state.

[0061] According to a preferred configuration, the fuel cell system can also operate under a safe shutdown operating condition. The safe shutdown operating condition can be set to be detected when the fuel cell system enters a critical state. For the safe shutdown operating condition, the supply of air to the air side and the supply of fuel to the fuel side can be interrupted.

[0062] Within the scope of this invention, "critical state" is specifically understood to mean the occurrence of component failure, leakage, or temperature, pressure, or reaction products beyond the operating limits of the fuel cell system.

[0063] Therefore, if a situation arises within the fuel cell system that could potentially endanger the equipment and / or personnel, the fuel cell system can be switched to a safe operating range. This can further improve the safety of the fuel cell system during operation.

[0064] According to another preferred configuration, the fuel cell system can also be operated under a test operating condition. This test operating condition can precede special operating conditions and / or normal operating conditions. The test operating condition can be adapted to be detected during process requirements for verifying the functionality of the fuel cell stack. Under the test operating condition, the actual operating parameters of the fuel cell stack (preferably including at least its actual temperature and / or the actual pressure occurring within it) can be compared with operating limits.

[0065] Therefore, the functionality and status of the fuel cell system can be inspected periodically, especially before it is put into operation. This can further improve the safety of the fuel cell system during operation.

[0066] According to another preferred configuration, the fuel cell system may have two electric heaters, which are respectively arranged in the duct sections of two parallel air supply paths. For each detected special operating condition, a primary electric heater and / or a secondary electric heater can be selected as the electric heater to regulate the temperature.

[0067] In this way, the heating capacity of two electric heaters can be utilized during operation. Depending on the heat demand, one or both heaters can be selected for operation. Furthermore, individual heaters can be connected to different components, allowing for targeted heating by specific heaters.

[0068] According to a preferred embodiment, under specific operating conditions, at least one electric heater can provide heat to the fuel cell system in a heating sequence. This heating sequence sequentially heats the catalytic converter for catalytic combustion of fuel exhaust gases, the fuel guiding pipeline, the reformer for fuel production, and the fuel cell stack to their respective operating temperatures for normal operation. Correspondingly, the flow path of the heated air can be selected for these specific operating conditions according to the heating sequence.

[0069] In this way, the need for protective or inert gases during the heating process can be eliminated. The heating sequence can be specifically understood as the order or predetermined sequence of the components of the fuel cell system. Preferably, the heating process schedule can be determined according to this order or priority.

[0070] Another aspect of the present invention relates to a computer program product with instructions that, when implemented by a computer, execute these instructions to perform the above-described method.

[0071] Another aspect of the invention relates to a control device for operating a fuel cell system. The fuel cell system has at least one fuel cell stack with an air side and a fuel side, and at least one electric heater for regulating the air temperature supplied to the fuel cell system through an air inlet portion. Furthermore, the fuel cell system operates under different operating conditions. These operating conditions include a normal operating condition for outputting electricity, and multiple special operating conditions during transitions to or from the normal operating condition. The control device has a detection module for detecting the current operating condition of the fuel cell system. Additionally, the control device has an operating condition control module for regulating the fuel cell system based on the detected current operating condition. Here, the operating condition control module is configured to regulate the air temperature via the at least one electric heater for the detected special operating conditions. Furthermore, the operating condition control module is configured to select at least one flow path of the electrically heated air in the fuel cell system from at least two possible flow path paths based on the detected special operating condition.

[0072] Another aspect of the invention relates to a fuel cell system. The fuel cell system has at least one fuel cell stack with an air side and a fuel side. Furthermore, the fuel cell system has at least one electric heater for regulating the air temperature supplied to the fuel cell system through an air inlet portion. The fuel cell system also has the control equipment described above for operating the fuel cell system under the different operating conditions mentioned above. The fuel cell system may be, for example, an SOFC or SOEC fuel cell system.

[0073] Using the computer program products, fuel cell systems, and control devices explained above, all the advantages of the method according to the present invention can be realized respectively.

[0074] To distinguish components or elements of the same kind or type, such as heat exchangers, shut-off devices, partial paths, or bypass paths, these components or elements will be uniformly numbered below and marked as First Component, Second Component, etc., i.e., First Heat Exchanger, Second Heat Exchanger, etc. This indication is only used to distinguish components or elements of the same kind or type and does not limit their characteristics.

[0075] The connections mentioned in this article include connections that guide fluids, such as connections that guide gases. These connections can be created by different paths or pipelines (e.g., pipes or hoses) that are coupled to each other. Flow-influencing devices, such as shut-off devices, can be placed within the connections.

[0076] The arrangement of heat exchangers in connections and their thermal coupling with other connections mentioned in this article should be understood as synonymous with these features due to the function of the heat exchanger. This is because the heat exchanger allows the exchange of heat between two flows in the corresponding connection, for example, in counter-current flow. In this sense, the heat exchanger is actually arranged within each of the two connections, and the heat exchanger also thermally couples the two connections to each other.

[0077] A shut-off device is used at least to stop or allow the flow of a corresponding fluid (especially a gas) in a connection. Depending on the design type of the shut-off device used, the flow rate can also be regulated. For this purpose, the shut-off device can have corresponding control electronics and sensor devices. Shut-off devices can be constructed in different ways, for example, as valves, gate valves, plug valves, or butterfly valves. Attached Figure Description

[0078] Other advantages, features, and details of the invention will become apparent from the following description. Embodiments of the invention are described in the description with reference to the accompanying drawings. The drawings are schematically illustrated as follows: Figure 1 An embodiment of the method according to the present invention is shown; Figure 2This invention illustrates an embodiment of a fuel cell system according to the invention and an embodiment of a control device according to the invention; Figure 3 Another embodiment of the fuel cell system according to the invention is shown, and its operation under verification operating conditions according to the invention is also illustrated. Figure 4 Show Figure 3 The operation of the fuel cell system shown according to the present invention under the first heating operation condition and the fourth cooling operation condition; Figure 5 Show Figure 3 The fuel cell system shown is operated under the second heating operating condition according to the present invention. Figure 6 Show Figure 3 The fuel cell system shown is operated under the third heating operating condition according to the present invention; Figure 7 Show Figure 3 The fuel cell system shown is operated under the fourth heating operating condition according to the present invention; Figure 8 Show Figure 3 The fuel cell system shown is operating under normal operating conditions. Figure 9 Show Figure 3 The fuel cell system shown is operated under the first cooling operating condition according to the present invention. Figure 10 Show Figure 3 The fuel cell system shown operates under the second cooling operating condition according to the present invention; Figure 11 Show Figure 3 The fuel cell system shown operates under the third cooling operating condition according to the present invention; The accompanying drawings illustrate different aspects and embodiments of the invention. Detailed Implementation

[0079] This invention relates to a method 1000 for operating a fuel cell system under different operating conditions. For example, in Figures 2 to 11 The illustrated fuel cell system 10 can be operated using method 1000. The operating condition can be interpreted in the first approximate step as an operating condition for normal operation, standby operation, or operation transition. In method 1000, the operating condition of the fuel cell system 10 is first detected, and then the fuel cell system 10 is adjusted based on the detection. Figure 1 The operating conditions detected and controlled in method 1000 are illustrated exemplarily.

[0080] In method 1000, the current operating condition of the fuel cell system 10 is detected. The current operating condition can be a normal operating condition for power output, or one of several special operating conditions transitioning from or to the normal operating condition. The fuel cell system 10 has at least one fuel cell stack 100 with an air side 110 and a fuel side 130. Based on the detected special operating condition, the temperature and flow path of the air supplied to the fuel cell system 10 through the air inlet 2101 are regulated by at least one electric heater 223, 243. This configuration of method 1000 can be particularly useful in… Figures 4 to 7 and Figures 9 to 11 The figures show the control of the fuel cell system 10 under specific operating conditions. Figure 8 This demonstrates the control measures for normal operating conditions.

[0081] The following will be based on Figure 1 The example shown is for Figure 2 and Figure 3 The method 1000 is described using an exemplary operating cycle of the fuel cell system 10. The exemplary operating cycle described herein includes: starting from a cold standby mode (BS80), the fuel cell system 10 is first heated (BS201 to BS204); Figures 4 to 7 ), activated operating condition (BS350; Figure 8 Then it returns to cold standby mode, for which the fuel cell system 10 must be cooled again. Figures 9 to 11 ).

[0082] Figure 4 Exemplary steps of method 1000 are shown when a special operating condition of the form of a first heating operating condition BS201 is detected. This can be done when a process request for heating is received, for example, in a cold standby mode. In the first heating operating condition BS201, the catalyst 511 disposed in the fuel cell system 10 is preferably heated. For this purpose, air from the air inlet section 2101 is heated by a secondary electric heater 243. Preferably, the air can be first directed through an air filter 210 and then delivered by a blower 211. To heat the catalyst 511 with heated air, the flow path of the heated air is directed from the secondary heater 243 to the catalyst 511. For this purpose, the connection points 241, 246, 512 and the shut-off device along the flow path can be adjusted accordingly, for example. In this way, the catalyst 511 is heated to the catalyst start-up temperature. Reaching the catalyst start-up temperature achieves catalytic combustion of the fuel exhaust gas. Figure 4The flow path of air from air inlet 2101 (where air enters the fuel cell system 10 through air inlet 2101), through catalyst 511, along exhaust gas outlet path 3500, to exhaust gas outlet 3502 (where exhaust gas leaves the fuel cell system 10 through exhaust gas outlet 3502) is shown in bold. Preferably, in the first heating operation condition BS201, another primary electric heater 223 can be additionally heated to the heater temperature.

[0083] Figure 5 The steps of method 1000 when a special operating condition in the form of a second heating operating condition BS202 is detected are illustrated exemplarily. For example, the second heating operating condition BS202 is implemented when at least the catalyst start-up temperature is detected at catalyst 511. In the second heating operating condition BS202, the fuel-guiding line should preferably be heated. A mixture of steam and natural gas is often used to produce hydrogen-rich fuel. Therefore, the fuel-guiding line must be heated before the steam is supplied to prevent the possibility of condensation. Part of the heat required for this can be provided by the primary electric heater 223. Thus, the flow path of the heated air is redirected here from the primary electric heater 223 to the air supply section 112 of the air side 110. Figure 5 The corresponding lines are shown in bold. Since the catalyst 511 is ready to catalytically convert the gas into a non-flammable gas, hot gas can be introduced into the fuel cell system 10 through the hot gas supply section 3101. The hot gas can be guided through the fuel line 3100 to the fuel supply section 131 of the fuel side 130. Here, the hot gas can receive heat from the heated air. Therefore, the heated hot gas can exit the fuel cell stack 100 through the fuel exhaust section 132 and be circulated through the circulation line 3700 by the circulation blower 311. Correspondingly, the fuel line 3100 and the circulation line 3700 can be heated to a minimum line temperature. The minimum line temperature can be the temperature from which water vapor condensation is prevented. Preferably, the circulation line 3700 extends from the branch point 371 of the fuel exhaust outlet path 3200 and leads to the connection point 317 of the fuel line 3100.

[0084] Figure 6 The steps of method 1000 are illustrated exemplarily when a special operating condition of the form of a third heating condition BS203 is detected. For example, the third heating condition BS203 is performed when the fuel line 3100 and the circulation line 3700 have at least a minimum line temperature. In the third heating condition BS203, the reformer 314, specifically configured to produce fuel for the fuel cell stack 100, should be heated to its activation temperature. The heat required for this is provided at least in part by the secondary electric heater 243. Figure 6The corresponding flow paths are shown in bold lines. Furthermore, the heated air exiting the air side 110 can provide heat. For example, it can thus heat the fuel entering the fuel side 130 via the air heat exchanger 214. The heated air from the fuel cell stack 100 can also be, for example, air, which is guided through a second air duct section 230 containing an air heat exchanger 235. The air heat exchanger 235 can transfer heat from the exhaust gas from the catalyst 511, which is very hot due to catalytic combustion. The heated air is thus guided to the inlet of the reformer heat exchanger 248 of the reformer 314. Preferably, the air is also further supplied to the catalyst 511. Advantageously, a secondary electric heater 243 is connected in series with the catalyst 511 and the reformer heat exchanger 248. The branch point 246 here can split the airflow into two flows. The heating process of the reformer 314 can be effectively controlled by controlling the opening of the control valve 247. The opening degree of control valve 247 can thus regulate the heating rate of reformer 314. Control valve 247 can be located between branch point 246 and reformer heat exchanger 248. Once reformer 314 reaches its activation temperature (also known as reformer start-up temperature), steam can be supplied to prevent carbon formation (carbon deposits) on the catalytic surface of reformer 314. This is in Figure 6 The dashed arrow indicates this. Water vapor can be generated in the water vapor generator 330. The generated water vapor can then be introduced into the fuel line 3100 through the connection point 331.

[0085] Figure 7 The steps of method 1000 are illustrated exemplarily when a special operating condition of the form of a fourth heating condition BS204 is detected. For example, the fourth heating operating condition BS204 can be implemented when the reformer 314 has at least the reformer initial temperature. In the fourth heating operating condition BS204, the fuel cell stack 100 should be heated to the minimum stack temperature. The heat required for this can be provided at least partially by the primary electric heater 223. Alternatively or supplementarily, a secondary electric heater 243 may also be used. Figure 7 (Not shown in the image) provides heat. Heated air from the primary heater 223 can be directly supplied to the fuel cell stack 100 via air supply path 2100. Figure 7 The corresponding flow path is shown in bold. Furthermore, thermal energy can be released by generating fuel from water vapor and hot gas in the reformer 314, and the resulting fuel, along with heated air, is supplied to the fuel cell stack 100.

[0086] Figure 8The steps of method 1000 are illustrated exemplarily when a normal operating condition BS350 corresponding to normal operation is detected. For example, normal operating condition BS350 can be achieved when the fuel cell stack 100 has at least a minimum stack temperature. During normal operation, air and fuel are supplied to the fuel cell stack 100 to generate an electric current. Preferably, electric heaters 223 and 243 are not required to maintain normal operation. For example, the required thermal energy can be provided solely by catalytic heating of the catalyst 511. Catalytic heating can be achieved, for example, by directing air from the air exit section 115 of the air side 110 and fuel exhaust gas from the fuel exhaust gas section 132 of the fuel side 130 to the catalyst 511. Therefore, the heat of the catalytic combustion exhaust gas in the catalyst 511 can be transferred to the supplied air via the air heat exchanger 235. The heat of the fuel exhaust gas can be transferred to the supplied fuel via two fuel heat exchangers 315 and 316. The fuel heat exchanger 315 can be arranged in a portion of the fuel exhaust gas outlet path 3200. The fuel heat exchanger 316 can preferably be arranged in a portion of the circulation line 3700. The generated current can be guided to the current output section 610 via the electrical connection 611 connected to the relay 614. Figure 8 The active components and flow paths are shown in thick lines.

[0087] Figure 9 The steps of method 1000 are illustrated exemplarily when a special operating condition of the form of a first cooling condition BS471 is detected, wherein the fuel cell system 10 is to be cooled. For example, the first cooling condition BS471 can be implemented when a process request to cool the fuel cell system 10 is issued. In the first cooling condition BS471, the fuel cell stack 100 should be cooled primarily to a first stack cooling temperature (e.g., 377°C) while maintaining a temperature gradient. For this purpose, air and fuel supplied to the fuel cell stack 100 can be used. For example, the fuel flow rate can be controlled until the first stack cooling temperature is reached. The temperature of the fuel and the reformer 314 can be controlled primarily by the secondary electric heater 243. For this purpose, the flow path of the air heated by the secondary heater 243 can be directed to the reformer heat exchanger 248. Figure 9 The corresponding flow path is shown in bold lines. Furthermore, the gradually cooled exhaust air from the air exit section 115 can be guided from the air side 110 to the inlet of the reformer heat exchanger 248. The temperature of the reformer 314 can be regulated here by controlling the control valve 247.

[0088] Figure 10The steps of method 1000 are illustrated exemplarily when a special operating condition of the form of a second cooling condition BS472 is detected. For example, the second cooling condition BS472 can be implemented when the fuel cell stack 100 is cooled to the first stack cooling temperature. In the second cooling condition BS472, the temperature of the reformer 314 should be cooled below its activation temperature. To this end, the air temperature is regulated by the secondary electric heater 243 and the air is directed to the catalyst 511 so that the catalyst 511 can continue to operate above its activation temperature. Figure 10 The corresponding flow path is shown in bold. Simultaneously, the control valve 247, which is preferably open in the first cooling operation condition BS471, is closed, allowing the reformer 314 to be cooled to its initial reformer temperature via hot gas and water vapor. Preferably, the water vapor supply is interrupted once the reformer 314 temperature drops to its initial reformer temperature, preventing carbon buildup.

[0089] Figure 11 The steps of method 1000 are illustrated exemplary when a special operating condition of the form of a third cooling operating condition BS473 is detected. For example, the third cooling operating condition BS473 can be implemented when the temperature of reformer 314 is lower than the initial temperature of reformer. In the third cooling operating condition BS473, the fuel cell stack 100 is preferably further cooled to room temperature. For this purpose, the air temperature is adjusted to at least the activation temperature of catalyst 511 by secondary electric heater 243, and the corresponding flow path of the heated air is directed to catalyst 511 to maintain the catalytic reaction within catalyst 511. Figure 11 The corresponding flow path is shown in bold. The temperature of the fuel cell stack 100 is controlled by adjusting the flow rates of hot gas and air until the second stack cooling temperature (preferably room temperature) is reached. Therefore, the fuel cell stack 100 can be cooled by the supplied air and hot gas.

[0090] The above has been discussed Figure 4 The steps of method 1000 are also illustrated exemplarily when a special operating condition of the form of cooling operating condition BS474 is detected. For example, a fourth cooling operating condition BS474 can be implemented when the fuel cell stack 100 has a temperature at most the second stack cooling temperature. In the fourth cooling operating condition BS474, the catalyst 511 should now also be cooled below its activation temperature, and in particular, cooled to room temperature. For this purpose, heat can be provided by the secondary electric heater 243. The flow path of the thus heated air is directed to the catalyst 511. Figure 4 The corresponding flow path is marked with a thick line. At the same time, additional hot gas is supplied to the catalyst 511 and its flow rate is regulated to further cool the catalyst 511.

[0091] Figure 1Other operating conditions are shown below: For example, at the start of method 1000, if a process request for verifying the functionality of the fuel cell system 10 has been made, the test operating condition BS10 can be detected. Components can then be tested. Figure 3 This can be used as an example to illustrate this operating condition.

[0092] In addition, the fuel cell system 10 may also have a cold standby operating condition BS80 outside of the diagnostic cycle. For example, this operating condition is detected if there is no process request for heating or operation and the fuel cell system 10 is at room temperature.

[0093] If the fuel cell system 10 has a sufficiently high temperature and is awaiting a request to enter normal operation, then the ready-to-operate condition BS330 can be executed. Under this operating condition, the primary focus should be on maintaining the temperature, pressure, and medium distribution.

[0094] Low-power operation modes BS340 and BS360 can be implemented immediately before or after normal operation, respectively. In this mode, power output can be increased or decreased gradually.

[0095] To address operational failures, method 1000 can also detect a safe shutdown operating condition BS500. Depending on the failure condition, a first critical operating condition BS501, a second critical operating condition BS502, and a third critical operating condition BS503 can be detected. For example, under the first critical operating condition BS501, operation can be immediately interrupted, and the fuel cell system 10 will enter a safe state. The second critical operating condition BS502 can specifically handle critical events occurring during full-load or partial-load operation, such as power outages. In the third critical operating condition BS503, critical events occurring during heating or cooling processes, such as power outages, can be specifically handled.

[0096] According to the present invention, the control device 20 includes a detection module 21 and a working condition control module 22, such as in Figure 2 As illustrated in the example diagram. The control device 20 can be connected to the fuel cell system 10 via the control connection 23. Preferably, the control device 20 is configured to implement the method 1000 according to the invention.

[0097] Figure 2The connections and connection points between the fuel cell system 10 and the external supply unit are further illustrated. Therefore, for example, a hot gas supply source 9310 can supply anode gas or hot gas, such as natural gas or methane, to the hot gas supply section 3101. A water supply source 9330 can supply water for generating water vapor to the water supply section 3301 of the fuel cell system 10. Air can be supplied to the fuel cell system 10 from the environment 9500 through the air inlet section 2101. Exhaust gas can be discharged from the fuel cell system 10 to the environment 9500 through the exhaust gas outlet section 3502. The coolant supply section 9800 can introduce coolant into the fuel cell system 10 through the coolant supply section 801 for cooling the exhaust gas, and then discharge the coolant through the coolant outlet section 802. Figure 3 As shown, coolant is fed to exhaust gas cooler 350.

[0098] Figure 3 Further details of an exemplary fuel cell system 10 with control device 10 according to the present invention are shown. Notably, the secondary electric heater 243 can simultaneously provide heat to both components due to the parallel piping guidance of the catalyst 511 and the reformer heat exchanger 248. The air supply path 2100 may specifically have four air duct sections 220, 230, 240, and 250, each having shut-off devices 222, 232, 242, and 252. The fourth air duct section 250 preferably has a heat exchanger 253 for transferring heat from the hot gas to the air upstream of the air side 110. The heated air can thus be introduced into the second air duct section 230 via the connection point 236 upstream of the air heat exchanger 235. The second air duct section 230 can supply directly to the air side 110. Furthermore, static mixers 213, 312, and 510 may also be provided within the fuel cell system 10.

[0099] The above explanation of the embodiments describes the present invention by way of example only.

[0100] List of reference numerals 1000 methods BS10 Inspection Operating Conditions BS80 Cold Standby Operation Condition BS201 First Heating Operation Condition BS202 Second heating operation condition BS203 Third Heating Operation Condition BS204 Fourth Heating Operation Condition BS330 Ready-to-operate status BS340 Low-power operation conditions BS350 Normal Operating Conditions BS360 Low-power operation conditions BS471 First Cooling Operation Condition BS472 Second Cooling Operation Condition BS473 Third Cooling Operation Condition BS474 Fourth Cooling Operation Condition BS500 Safe Shutdown Operation Conditions BS501 First Critical Operating Condition BS502 Second Critical Operating Condition BS503 Third Critical Operating Condition 10. Fuel Cell System 100 fuel cell stack 110 Air Side 112 Air Intake Section 115 Air leaving part 130 Fuel Side 131 Fuel Supply Section 132 Fuel Exhaust Gas Section 210 Air Filter 211 Blower 213 Static Air Mixer 214 Other air heat exchangers 220 First Air Piping Section 222 Cut-off device 223 Primary Electric Heater 230 Second Air Piping Section 232 Cut-off device 235 Air Heat Exchanger 236 Connection Points 237 Connection Point 240 Third air piping section 241 Connection Point 242 Cut-off device 243 Secondary Electric Heater 246 branch points 247 Control Valve 248 Reformer heat exchanger 249 Connection Points 250 Fourth Air Piping Section 252 Cut-off device 253 Other air heat exchangers 311 Circulating Blower 312 Static Fuel Mixer 314 Reformer 315 and 316 fuel heat exchangers 317 Connection Point 330 Steam Generator 331 Connection Point 350 Exhaust Gas Cooler 371 branch points 510 Static Exhaust Gas Mixer 511 Catalyst 512 Connection Points 610 Current Output Section 611 Electrical connection 614 Relay 801 Coolant Supply Section 802 Coolant Drainage Section 2100 Air Supply Path 2101 Air Intake Section 3101 Hot Gas Supply Section 3200 Fuel Exhaust Gas Discharge Path 3301 Water Supply Section 3500 Exhaust Gas Discharge Path 3502 Exhaust Gas Discharge Section 3700 Circulation Piping 9310 Hot gas supply source 9330 Water Supply Source 9500 Environment 9800 Coolant Supply Department 20 Control equipment 21 Detection Module 22 Operating Condition Control Module 23 Control Connection

Claims

1. A method (1000) for operating a fuel cell system (10), the fuel cell system (10) having at least one fuel cell stack (100) with an air side (110) and a fuel side (130), and the fuel cell system operating under different operating conditions, the operating conditions including a normal operating condition (BS350) for outputting electricity and a plurality of special operating conditions during transition to or from the normal operating condition (BS350), the method (1000) comprising the following steps: - Detect the current operating condition of the fuel cell system (10); - Adjust the fuel cell system (10) according to the detected current operating conditions, wherein for the detected special operating conditions: The air temperature that can be supplied to the fuel cell system (10) through the air inlet section (2101) is regulated by at least one electric heater (223, 243), and Based on the detected special operating conditions, the direction of at least one flow path of the electrically heated air in the fuel cell system (10) is selected from at least two possible flow path directions of the fuel cell system (10).

2. The method (1000) according to claim 1, characterized in that: - The first heating operation condition (BS201) used to heat the fuel cell system (10) is detected as one of the special operation conditions for transitioning to the normal operation condition; and -For the first heating operating condition (BS201) which is detected as a special operating condition: The flow path of the heated air is selected, the flow path being from at least one heater (243) toward the catalyst (511) of the fuel cell system (10) for catalytic combustion of fuel exhaust gas, so as to heat the catalyst (511) to its catalyst activation temperature. The first heating operation condition (BS201) preferably continues at least until the catalyst (511) reaches the catalyst activation temperature, and Preferably, the air temperature is controlled by the electric heater (223) according to the catalyst heating curve.

3. The method (1000) according to any one of the preceding claims, characterized in that: - The second heating operating condition (BS202) used to heat the fuel cell system (10) is detected as one of the special operating conditions for transitioning to the normal operation, wherein, preferably, the second heating operating condition (BS202) immediately follows the first heating operating condition (BS201); and -For the second heating operation condition (BS202) detected as a special operating condition: Hot gas, preferably methane, is supplied through fuel line (3100) to fuel supply section (131) of fuel side (130) to receive heat from heated air in fuel cell stack (100); The supplied hot gas circulates in the circulation line (3700) of the fuel cell system (10) to heat the fuel-guiding line (3100, 3700) of the fuel cell system (10), the circulation line (3700) extending between a portion of the fuel exhaust outlet section (132) for exhausting fuel gas on the fuel side (130) and a portion of the fuel line (3100) upstream of the fuel supply section (131); Preferably, the air temperature is controlled by at least one electric heater (243) according to the fuel line heating curve; and Select the flow path of the heated air from the air supply section (112) of at least one heater (243) to the air side (110); Preferably, the second heating operation condition (BS202) continues until at least the circulation line (3700) and the fuel line (3100) have a minimum line temperature, which is preferably at least the water vapor condensation temperature.

4. The method (1000) according to any one of the preceding claims, characterized in that: - The third heating operating condition (BS203) used to heat the fuel cell system (10) is detected as one of the special operating conditions transitioning to normal operation, wherein preferably the third heating operating condition (BS203) immediately follows the second heating operating condition (BS202); and -For the third heating operating condition (BS203) detected as a special operating condition (BS203): Select a flow path for the heated air, the flow path being directed from at least one heater (243) toward the inlet of the reformer heat exchanger (248) of the reformer (314) of the fuel cell system (10) for generating fuel to be supplied to the fuel side (130), so as to heat the reformer (314) to the reformer activation temperature of the reformer. and Preferably, an additional flow path for the heated air is selected, the additional flow path leading from at least one heater (243) to the catalyst (511) of the fuel cell system (10) for catalytic combustion of fuel exhaust gas; Preferably, the temperature of the reformer (314) is adjusted to the reformer activation temperature by regulating the flow rate of the heated air passing through the reformer heat exchanger (248) according to the reformer heating curve. and Once the reformer (314) reaches the reformer activation temperature, steam is supplied to the reformer (314).

5. The method (1000) according to any one of the preceding claims, characterized in that: - The fourth heating operating condition (BS204) used for heating the fuel cell system (10) is detected as one of the special operating conditions transitioning to normal operation, wherein, preferably, the fourth heating operating condition (BS204) immediately follows the third heating operating condition (BS203); and - Regarding the fourth heating operating condition (BS204) as a detected special operating condition: Select a flow path for the heated air, the flow path being directed from at least one electric heater (223) toward the air side (110) to heat the fuel cell stack (100) to a minimum stack temperature; Steam and hot gas are supplied to the reformer (314) to generate fuel for supply to the fuel side (130); The generated fuel and heated air are supplied to the fuel cell stack (100), respectively; and Preferably, the fourth heating operation condition (BS204) continues until the fuel cell stack (100) has the lowest stack temperature.

6. The method (1000) according to any one of the preceding claims, characterized in that: -Detect the normal operating conditions (BS350) corresponding to normal operation; and -For the detected normal operating conditions (BS350): Air and fuel are supplied to the fuel cell stack (100). An electric current is generated in the fuel cell stack (100) by the supplied air and fuel; Preferably, at least one electric heater (223, 243) is deactivated; and The temperature of the fuel cell stack (100) is regulated by catalytic heating.

7. The method (1000) according to any one of the preceding claims, characterized in that: - The first cooling operating condition (BS471) used to cool the fuel cell system (10) is detected as one of the special operating conditions transitioning from normal operation; and -For the first cooling operating condition (BS471) detected as a special operating condition: Preferably, the air temperature is regulated according to a cooling curve by at least one electric heater (243); Select the flow path of the heated air, the flow path being directed from at least one heater (243) toward the inlet of the reformer heat exchanger (248) of the reformer (314) of the fuel cell system (10) for generating fuel to be supplied to the fuel side (130). In addition, exhaust gas is supplied from the air side (110) to the inlet of the reformer heat exchanger (248); Preferably, the temperature of the reformer (314) is controlled by adjusting the flow rate of the gas mixture of heated air and exhaust gas supplied through the reformer heat exchanger (248) according to the reformer cooling curve. Preferably, based on the stack cooling profile, the temperature of the fuel cell stack (100) is controlled to a first stack cooling temperature by adjusting the flow rate of fuel preferably supplied from the reformer (314) to the fuel side (130), wherein the first stack cooling temperature is lower than the minimum stack temperature required for normal operation; and Preferably, the first cooling operation condition (BS471) continues until the first pile cooling temperature is reached.

8. The method (1000) according to any one of the preceding claims, characterized in that: - The second cooling operating condition (BS472) used to cool the fuel cell system (10) is detected as one of the special operating conditions transitioning from normal operation; and -For the second cooling operating condition (BS472) as a detected special operating condition: Preferably, the air temperature is controlled according to a cooling curve by at least one electric heater (243); The flow path of the heated air is selected from at least one heater (243) toward the catalyst (511) of the fuel cell system (10) for catalytic combustion of fuel exhaust gas, so that the catalyst (511) operates at a temperature above its catalyst activation temperature. By supplying hot gas and water vapor to the reformer (314) of the fuel cell system (10) for heat extraction until the reformer (314) has a temperature at most the reformer activation temperature, the temperature of the reformer (314) is regulated to the reformer activation temperature to produce fuel for the fuel side (130). and Once the reformer (314) reaches a temperature below the reformer activation temperature, the supply of steam to the reformer (314) is stopped.

9. The method (1000) according to any one of the preceding claims, characterized in that: - The third cooling operating condition (BS473) used to cool the fuel cell system (10) will be detected as one of the special operating conditions transitioning from normal operation; and -For the third cooling operating condition (BS473) as a detected special operating condition: The air temperature is preferably adjusted to the catalyst activation temperature by means of at least one electric heater (243) according to a cooling curve; The flow path of the heated air is selected, the flow path being from at least one heater (243) to the catalyst (511) of the fuel cell system (10) for catalytic combustion of fuel exhaust gas, to maintain the active operation of the catalyst (511); and Preferably, the temperature of the fuel cell stack (100) is adjusted to the second stack cooling temperature by regulating the flow rate of hot gas and air that can be supplied to the fuel supply section (131) on the fuel side (130) according to the stack cooling curve.

10. The method (1000) according to any one of the preceding claims, characterized in that: - The fourth cooling operating condition (BS474) used to cool the fuel cell system (10) was detected as one of the special operating conditions transitioning from normal operation; and -For the fourth cooling operating condition (BS474) that is detected as a special operating condition: The flow path of the heated air is selected, the flow path being from at least one heater (243) toward the catalyst (511) of the fuel cell system (10) for catalytic combustion of fuel exhaust gas, so as to cool the catalyst (511) below its catalyst activation temperature; and Preferably, the air temperature is adjusted to a temperature below the catalyst activation temperature by at least one electric heater (243) according to a cooling curve; Preferably, based on the catalyst cooling curve, the temperature of the catalyst (511) is adjusted to the catalyst settling temperature by regulating the flow rate of hot gas and air supplied to the fuel supply section (131) that can be supplied to the fuel side (130) through the catalyst (511).

11. The method (1000) according to any one of the preceding claims, characterized in that: The fuel cell system (10) has two electric heaters (223, 243), which are respectively arranged in one of two parallel pipe sections (220, 240) of the air supply path (2100) of the fuel cell system (10); and For each detected special operating condition, a primary electric heater (223) and / or a secondary electric heater (243) are selected as electric heaters (223, 243) for regulating air temperature according to the corresponding special operating condition.

12. The method (1000) according to any one of the preceding claims, characterized in that, During the special operating conditions of heating the fuel cell system (10), heat is provided by at least one electric heater (223, 243) in a heating sequence for heating, wherein the catalyst (511) for catalytic combustion of fuel exhaust gas, the fuel guiding pipelines (3100, 3700), the reformer (314) for fuel production, and the fuel cell stack (100) are successively heated to their operating temperatures for normal operation in the heating sequence; and The flow path of the heated air is selected according to the heating sequence for these special operating conditions.

13. A computer program product comprising instructions that, when executed by a computer, cause the computer to perform the method (1000) according to any one of claims 1 to 12.

14. A control device (20) for operating a fuel cell system (10) having at least one fuel cell stack (100), the fuel cell stack (100) having an air side (110) and a fuel side (130), and the fuel cell stack (100) having at least one electric heater (223, 243) for regulating the air temperature of air supplied to the fuel cell system (10) through an air inlet (112), wherein, The fuel cell system (10) operates under different operating conditions, including a normal operating condition (BS350) for outputting electricity and several special operating conditions for transitioning to or from the normal operating condition (BS350). Its features are: - A detection module (21) for detecting the current operating condition of the fuel cell system (10), and - A condition control module (22) for adjusting the fuel cell system (10) according to the detected current operating conditions. The operating condition control module (22) is configured to regulate the air temperature by at least one electric heater (223, 243) for detected special operating conditions, and select the direction of at least one flow path of the electrically heated air in the fuel cell system (10) from at least two possible flow path directions of the fuel cell system (10) according to the detected special operating conditions.

15. A fuel cell system (10), preferably a solid oxide fuel cell system, comprising: - At least one fuel cell stack (100), the fuel cell stack (100) having an air side (110) and a fuel side (130), and - At least one electric heater (223, 243) is provided for regulating the air temperature that can be supplied to the fuel cell system (10) through the air intake section (112). Its features are: - The control device (20) according to claim 14 is used to operate the fuel cell system (10) under different operating conditions, the operating conditions having a normal operating condition (BS350) for outputting electricity and a number of special operating conditions when transitioning to or from the normal operating condition (BS350).

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