Fuel cell device, method for operating a fuel cell device, and use of a nernst cell unit of a fuel cell system

Abstract

The invention relates to a fuel cell device (10) having: at least one line system (12) for guiding a fuel; at least one reformer (14), which is connected to the line system (12), for reforming the fuel; and at least one Nernst cell unit (16, 18), in particular a lambda sensor, for detecting a process fluid parameter of a fluid in the line system (12). The Nernst cell unit (16, 18) is arranged upstream of the reformer (14).

Description

[0001] Description

[0002] FUEL CELL DEVICE, METHOD FOR OPERATING A FUEL CELL DEVICE AND USE OF A FUEL CELL UNIT OF A FUEL CELL SYSTEM

[0003] State of the art

[0004] A fuel cell device has already been proposed with at least one line system for guiding a fuel, with at least one reformer connected to the line system for reforming the fuel and with at least one Nernst cell unit, in particular a lambda probe, for detecting a process fluid parameter of a fluid located in the line system.

[0005] Disclosure of the invention

[0006] The invention is based on a fuel cell device with at least one line system for guiding a fuel, with at least one reformer connected to the line system for reforming the fuel and with at least one Nernst cell unit, in particular a lambda probe, for detecting a process fluid parameter of a fluid located in the line system.

[0007] It is proposed that the Nernst cell unit be arranged upstream of the reformer. The Nernst cell unit is preferably designed as a lambda probe. The Nernst cell unit preferably comprises at least one Nernst cell or an electrochemical cell, in particular a fuel cell, which is connected as a Nernst cell. The lambda probe can be designed as a jump-type lambda probe or as a broadband lambda probe. The lambda probe is preferably designed as a finished part. Alternatively, the lambda probe is designed specifically for the fuel cell device.

[0008] The line system preferably comprises a fuel supply. The fuel supply preferably comprises a fuel connection to a connection of an external fuel source. The fuel supply preferably comprises at least one supply connection for transferring the fuel to a fuel cell unit, which is provided for electrochemical conversion of the fuel. The fuel comprises, for example, hydrogen, ammonia, methane and / or another hydrocarbon as the main energy carrier. The fuel is in the form of natural gas or biogas, for example. The reformer is preferably arranged along the fuel supply. The reformer is preferably arranged upstream of the supply connection of the fuel supply for the fuel cell unit. The fuel cell device preferably comprises a fluid conveying unit, preferably a blower or compressor, for conveying the fuel through the line system.The fluid delivery unit is arranged along the fuel supply line, preferably upstream of the reformer. The line system preferably comprises at least one recirculation line for feeding exhaust gas produced from the fuel back into the fuel supply line. The recirculation line preferably opens into the fuel supply line upstream of the reformer and preferably downstream of the fluid delivery unit. The fuel cell device preferably comprises a recirculation delivery unit arranged along the recirculation line for conveying the exhaust gas through the recirculation line. The Nernst cell unit is preferably arranged in the fuel supply line or in the recirculation line. The Nernst cell unit is particularly preferably arranged downstream of the fluid delivery unit or the recirculation delivery unit.The Nernst cell unit is most preferably arranged in the vicinity of a discharge point of the recirculation line into the fuel supply. A "near vicinity" is preferably understood to mean a distance of less than 100 cm, preferably less than 50 cm, and particularly preferably less than 25 cm, from the discharge point in a downstream or upstream direction. The fuel cell device preferably comprises an evaluation unit for evaluating the process fluid parameter. The evaluation unit preferably comprises a processor unit and a memory unit, as well as an operating program stored in the memory unit. The evaluation unit is preferably provided to monitor a flushing process of the line system.The purging process is preferably intended to remove oxygen, in particular air, from the line system by supplying an inert fluid and / or to chemically bind the oxygen using a reaction fluid. The inert fluid is, for example, molecular nitrogen or water. The reaction fluid is, for example, the fuel, in particular molecular hydrogen.

[0009] The evaluation unit is preferably provided to determine an oxygen content of the fluid in the line system as a function of the process fluid parameter. In an advantageously simple embodiment, the evaluation unit is provided to detect the presence or absence of oxygen within the line system. In the advantageously simple embodiment, the lambda probe is preferably designed as a step-type lambda probe. In an advantageously precise embodiment, the evaluation unit is provided to quantify an oxygen content of the fluid. In the advantageously precise embodiment, the lambda probe is preferably designed as a broadband lambda probe. The evaluation unit can be designed separately from the lambda probe or integrated into the lambda probe.The evaluation unit preferably comprises at least one data interface to an output of the fluid process parameter and / or a variable dependent on the fluid process parameter, such as a purge progress indication and / or a manipulated variable for controlling or regulating the fuel cell device.

[0010] "Intended" should be understood, in particular, to mean specifically programmed, designed, and / or equipped. The fact that an object is intended for a specific function should be understood, in particular, to mean that the object fulfills and / or performs this specific function in at least one application and / or operating state. The configuration according to the invention advantageously allows the fuel cell device to be operated safely. In particular, an advantageously reliable and reproducible flushing process of the line system can be achieved. Furthermore, load operation of the fuel cell device can advantageously be adjusted quickly.

[0011] It is further proposed that the Nernst cell unit be arranged in a fuel supply of the line system, in particular the one already mentioned. The Nernst cell unit is preferably arranged in the fuel supply at or downstream of the point where the recirculation line joins the fuel supply. The inventive design advantageously allows a fuel-oxygen ratio in the line system to be precisely monitored.

[0012] It is further proposed that the Nernst cell unit or another Nernst cell unit be arranged in a recirculation line of the piping system, in particular the one already mentioned. The inventive design allows for an advantageously reliable determination of the oxygen content remaining in the piping system.

[0013] Furthermore, a fuel cell system is proposed with at least one fuel cell unit for electrochemically converting a fuel and with at least one fuel cell device according to the invention for supplying the fuel cell unit with the fuel. The fuel cell unit preferably comprises at least one fuel cell, particularly preferably at least one high-temperature fuel cell. The at least one fuel cell is preferably designed as a solid oxide fuel cell or as a molten carbonate fuel cell. Alternatively, the at least one fuel cell is designed as a phosphoric acid fuel cell, a direct methanol fuel cell, a polymer electrolyte fuel cell, or the like. A fuel electrode of the at least one fuel cell is preferably connected to the supply connection of the line system.The fuel cell unit preferably comprises a plurality of fuel cells arranged in one or more stacks. The fuel cells are preferably electrically connected in series and, in particular, are intended for joint operation. The fuel cell system preferably comprises peripheral devices for operating the at least one fuel cell. Examples of peripheral devices include an afterburner for thermally converting fuel residues downstream of the at least one fuel cell, at least one internal exhaust gas heat exchanger for exhaust gas heat recovery, an oxygen supply unit for supplying an oxygen electrode of the at least one fuel cell with an oxygen-containing fluid, in particular air, and / or the like. The configuration according to the invention advantageously allows a purging process of the fuel cell system to be reliably monitored.

[0014] Furthermore, a method for operating a fuel cell device according to the invention is proposed, wherein in at least one method step of the method, the Nernst cell unit detects a process fluid parameter of a fluid located in the line system upstream of the reformer. The method preferably comprises a purging process for removing oxygen, in particular air, and / or fuel from the line system. The purging process is preferably provided to prevent an explosive oxygen-fuel mixture within the line system. The purging process is preferably carried out before or overlapping with commissioning of the fuel cell unit, in particular for purging oxygen before or overlapping with a, in particular limited, fuel feed into the line system.The purging process is preferably carried out after or overlapping with a shutdown of the fuel cell unit, in particular to purge the fuel before or overlapping with the feeding or inflow of oxygen, in particular air, into the line system. The Nernst cell unit preferably records the process fluid parameter during the purging process. The Nernst cell unit preferably records the process fluid parameter continuously at least during the purging process, in particular at least once every 30 seconds, preferably at least once every 10 seconds, particularly preferably at least once per second. The configuration according to the invention advantageously allows the purging process to be reliably monitored. Furthermore, the purging process can advantageously be ended early, since a time safety buffer at the end of the purging process can advantageously be kept short.It is further proposed that, in at least one method step of the method, load operation of the fuel cell device is set as a function of the process fluid parameter. The evaluation unit preferably decides, as a function of the process fluid parameter, when the purging process can be terminated. The evaluation unit preferably terminates the purging process automatically, in particular by controlling the fluid conveying unit, the recirculation conveying unit and / or valves of the fuel cell device. Alternatively, the evaluation unit outputs an enable signal indicating that the purging process can be terminated, for example manually or by a higher-level external control system. Preferably, after the purging process, the evaluation unit initiates load operation of the fuel cell unit or a shutdown process or standby operation of the fuel cell device.In addition to the process fluid parameter, the evaluation unit preferably evaluates at least one further measured value to assess the progress of the flushing process. For example, the evaluation unit processes a temperature profile and / or a pressure profile of the fluid in the line system as a further measured value to assess the progress of the flushing process. The inventive design advantageously allows for rapid initiation of load operation.

[0015] It is further proposed that, in at least one method step of the method, a fuel feed is adjusted as a function of the process fluid parameter. The fuel cell device is preferably designed for a maximum nominal fuel flow, for example in the form of a maximum nominal pressure, a maximum nominal volume flow, a maximum nominal mass flow, or the like. During the purging process, the evaluation unit preferably limits the fuel feed to a value below the maximum nominal flow. During a transition from the purging process to load operation, the evaluation unit preferably releases the maximum nominal fuel flow for controlling or regulating an electrical power generated by the fuel cell unit.

[0016] During the purging process, the evaluation unit preferably adjusts the fuel feed depending on the process fluid parameter. Particularly preferably, the evaluation unit uses the process fluid parameter as a control variable for adjusting the fuel feed. The evaluation unit preferably correlates the fuel feed negatively with the determined oxygen content of the fluid in the line system. The evaluation unit preferably starts the fuel feed at a zero value. The evaluation unit preferably increases the fuel feed step by step. Particularly preferably, after a change in the fuel feed, the evaluation unit waits for a predetermined minimum reaction time of the fuel cell device before making a further change in the fuel feed. The evaluation unit preferably increases the fuel feed until a safety threshold is reached.The safety threshold value is preferably the explosion limit, in particular the lower one, of the fluid present in the line system minus a safety buffer, in particular less than 50%, preferably at least less than 25%, particularly preferably at least less than 10% of the explosion limit. The evaluation unit preferably determines the explosion limit as a function of the detected fluid process parameter. The inventive design allows the fuel concentration to be advantageously and quickly increased during the purging process, in particular so that load operation is advantageously achieved quickly after the purging process.

[0017] It is further proposed that in at least one method step of the method, a comparison measurement be carried out in order to determine a further process fluid parameter. The evaluation unit preferably compares an output signal of the Nernst cell unit in the fuel supply with an output signal of the Nernst cell unit in the recirculation line in order to determine the further process fluid parameter. The further process fluid parameter is preferably a fuel content, in particular hydrogen content, of the fluid located in the line system between the outlet point of the recirculation line and the reformer. The evaluation unit preferably uses the further process fluid parameter as a controlled variable for adjusting the fuel feed. The embodiment according to the invention advantageously allows a concentration of the fuel to be determined directly.

[0018] It is further proposed that, in at least one method step of the method, the process fluid parameter is determined by means of a machine learning process. Preferably, the machine learning process evaluates the process fluid parameter and / or the further process fluid parameter in order to assess the progress of the purging process. Preferably, the machine learning process evaluates the at least one further measured value in order to assess the progress of the purging process. The machine learning process can be implemented on the evaluation unit. Alternatively, the fuel cell device comprises a communication interface for communication with an external data processing unit implementing the machine learning process, for example, a server, a cloud service, or the like. The machine learning process can be embodied, for example, as an artificial neural network, a classifier, a cluster analysis, or the like.The design according to the invention allows the rinsing process to be advantageously analyzed and monitored precisely.

[0019] Furthermore, the use of a Nernst cell unit, in particular a lambda probe, of a fuel cell system, particularly one arranged as an alternative to the fuel device according to the invention, for monitoring a purging process of the fuel cell system is proposed. The Nernst cell unit of the fuel cell system can be arranged, for example, at an outlet of a fuel cell unit of the fuel cell system or in a recirculation line of the fuel cell system upstream of a recirculation conveying unit of the fuel cell system in order to analyze an exhaust gas emerging from the fuel cell unit, in particular during load operation of the fuel cell unit. The Nernst cell unit preferably detects a fluid process parameter of a fluid present in the fuel cell system during a purging process of the fuel cell system.An evaluation unit of the fuel cell system preferably processes the fluid process parameter to monitor the progress of the purging process, determine the end of the purging process, and / or initiate load operation. The inventive design allows the purging process to be monitored and advantageously terminated early.

[0020] The fuel cell device according to the invention, the fuel cell system according to the invention, the method according to the invention, and / or the use according to the invention are not intended to be limited to the application and embodiment described above. In particular, the fuel cell device according to the invention, the fuel cell system according to the invention, the method according to the invention, and / or the use according to the invention may, in order to fulfill a functionality described herein, have a number of individual elements, components, units, and method steps that differs from the number stated herein. Furthermore, in the value ranges specified in this disclosure, values ​​within the stated limits are also to be considered disclosed and can be used arbitrarily.

[0021] Drawings

[0022] Further advantages will become apparent from the following description of the drawings. The drawings illustrate an exemplary embodiment of the invention. The drawings, the description, and the claims contain numerous features in combination. Those skilled in the art will also expediently consider the features individually and combine them into useful further combinations.

[0023] They show:

[0024] Fig. 1 A schematic representation of a fuel cell system according to the invention and

[0025] Fig. 2 is a schematic flow diagram of a method according to the invention.

[0026] Description of the embodiment

[0027] Figure 1 shows a fuel cell system 24. The fuel cell system 24 comprises at least one fuel cell unit 26 for electrochemically converting a fuel. The fuel cell unit 26 preferably comprises at least one fuel electrode 30. The fuel cell unit 26 preferably comprises at least one oxygen electrode 32. The fuel cell system 24 comprises at least one fuel cell device 10 for supplying the fuel cell unit 26 with a fuel. The fuel cell device 10 comprises at least one line system 12 for conveying the fuel. The line system 12 preferably comprises a fuel supply 20. The fuel supply 20 is preferably connected to an inlet of the fuel electrode 30. The fuel cell device 10 preferably comprises a fluid delivery unit (not shown here) arranged on the fuel supply 20 for conveying the fuel through the line system 12.The fuel cell device 10 comprises at least one reformer 14 connected to the line system 12 for reforming the fuel. The reformer 14 is preferably arranged upstream of the fuel cell unit 26 at the fuel supply 20. The fuel cell device 10 preferably comprises at least one recirculation line 22. The recirculation line 22 preferably connects an outlet of the fuel electrode 30 to the fuel supply 20. A point where the recirculation line 22 opens into the fuel supply 20 is preferably arranged upstream of the reformer 14. The fuel cell device 10 preferably comprises a recirculation conveying unit (not shown here) for conveying a fluid exiting the fuel cell unit 26 through the recirculation line 22.

[0028] The fuel cell device 10 preferably comprises a desulfurizer 46 for desulfurizing the fuel. The desulfurizer 46 is arranged at the fuel supply 20, preferably upstream of the outlet point. The fuel cell device 10 comprises, for example, an evaporator 44 for feeding steam into the line system 12. A feed point of the evaporator 44 into the fuel supply is preferably arranged upstream of the outlet point. The fuel cell device 10 preferably comprises a fuel preheater 40 for heating the fuel. The fuel preheater 40 is arranged at the fuel supply 20, preferably upstream of the outlet point.

[0029] The fuel cell system 24 preferably comprises an oxygen supply unit 34 for supplying the fuel cell unit 26 with an oxygen-containing fluid, in particular air. The oxygen supply unit 34 is preferably connected to an inlet of the oxygen electrode 32. The oxygen supply unit 34 preferably comprises an oxygen preheater 42 for heating the oxygen-containing fluid. The oxygen preheater 42 is preferably arranged upstream of the fuel cell unit 26.

[0030] The fuel cell system 24 preferably comprises an afterburner 36 for thermally utilizing fuel residues exiting the fuel cell unit 26. The afterburner 36 is preferably connected to the outlet of the fuel electrode 30 and to an outlet of the oxygen electrode 32. The fuel cell system 24 preferably comprises at least one exhaust gas heat exchanger 38 for recovering heat from an exhaust gas of the afterburner 36. The exhaust gas heat exchanger 38 is thermally coupled, for example, to the fuel preheater 40, the oxygen preheater 42, and / or the evaporator 44, in particular formed integrally with at least one of these components.

[0031] The fuel cell device 10 comprises at least one Nernst cell unit 16. The Nernst cell unit 16 is preferably part of a lambda probe, preferably a broadband lambda probe, or alternatively a step-wave lambda probe. The Nernst cell unit 16 is arranged upstream of the reformer 14. The Nernst cell unit 16 is arranged in the fuel supply 20 of the line system 12. The Nernst cell unit 16 is preferably arranged at or downstream of the outlet point of the recirculation line 22. The Nernst cell unit 16 is provided for detecting a process fluid parameter of a fluid located in the line system 12.

[0032] The fuel cell device 10 preferably comprises a further Nernst cell unit 18. The further Nernst cell unit 18 is preferably part of a lambda probe, preferably a broadband lambda probe, alternatively a step-through lambda probe. The further Nernst cell unit 18 is arranged upstream of the reformer 14. The further Nernst cell unit 18 is arranged in the recirculation line 22 of the line system 12. The further Nernst cell unit 18 is preferably arranged at or upstream of the outlet point of the recirculation line 22. The further Nernst cell unit 18 is provided for detecting a process fluid parameter of a fluid located in the line system 12. The fuel cell device 10 preferably comprises an evaluation unit 48 for processing the process fluid parameter and / or the further process fluid parameter.

[0033] Figure 2 shows a flowchart of a method 28 for operating the fuel cell device 10. The method 28 preferably comprises a detection step 50. The method 28 preferably comprises an evaluation step 52. The method 28 preferably comprises an output step 54 and / or a control or regulating step 56.

[0034] In the detection step 50, the Nernst cell unit 16 detects the process fluid parameter of a fluid located in the line system 12 upstream of the reformer 14. The detection step 50 is preferably carried out during a purging process of the line system 12. In the detection step 50, the further Nernst cell unit 18 preferably detects a further value of the process fluid parameter

[0035] In evaluation step 52, evaluation unit 48 preferably evaluates the process fluid parameter to determine an oxygen content of the fluid present in the line system. In evaluation step 52, evaluation unit 52 preferably compares the value of the fluid process parameter recorded with Nernst cell unit 16 and the value recorded with the further Nernst cell unit 18 to determine a further process fluid parameter. The further process fluid parameter is preferably a fuel content, in particular a hydrogen content, of the fluid present in line system 12. The process fluid parameter and / or the further process fluid parameter can be evaluated, for example, using explicit mathematical calculation rules or using a machine learning process.

[0036] In output step 54, evaluation unit 48 preferably outputs a progress of the purging process, in particular a composition of the fluid present in line system 12 determined from the fluid process parameter and / or the further fluid process parameter. Evaluation unit 48 preferably executes output step 54 upon startup of fuel cell unit 26, when the oxygen content falls below a minimum detection threshold to indicate that the purging process has ended or can be ended. Evaluation unit 48 preferably executes output step 54 upon shutdown of fuel cell unit 26, when the fuel content falls below a minimum detection threshold to indicate that the purging process has ended or can be ended. In some embodiments, evaluation unit 48 executes output step 54 regularly, in particular continuously, at least during the purging process.

[0037] In the control or regulation step 56, the evaluation unit 48 adjusts the fuel feed depending on the process fluid parameter and / or the further process fluid parameter. When the fuel cell unit 26 is started up, the evaluation unit 48 preferably increases the fuel feed stepwise, as long as the composition of the fluid in the line system 12 is below the lower explosion limit minus a safety buffer. If the oxygen content of the fluid in the line system 12 falls below the minimum detection threshold, the evaluation unit 48 preferably initiates load operation of the fuel cell unit 26. During load operation, the evaluation unit 48 preferably controls or regulates the fuel feed depending on a predetermined operating point, in particular an electrical current, temperature, and / or heat output, of the fuel cell unit 26.

[0038] When the fuel cell unit 26 is shut down, the evaluation unit 48 gradually increases the air supply to the line system 12, for example, as long as the composition of the fluid in the line system 12 is above the upper explosion limit plus a safety buffer. Alternatively, when the fuel cell unit 26 is shut down, the evaluation unit 48 flushes water vapor into the line system 12 as long as the composition of the fluid in the line system 12 is such that fuel gas is present in the line system 12.

Claims

Claims 1. A fuel cell device comprising at least one line system (12) for conducting a fuel, at least one reformer (14) connected to the line system (12) for reforming the fuel, and at least one Nernst cell unit (16, 18), in particular a lambda probe, for detecting a process fluid parameter of a fluid located in the line system (12), characterized in that the Nernst cell unit (16, 18) is arranged upstream of the reformer (14).

2. Fuel cell device according to claim 1, characterized in that the Nernst cell unit (16) is arranged in a fuel supply (20) of the line system (12).

3. Fuel cell device according to claim 1 or 2, characterized in that the Nernst cell unit or a further Nernst cell unit (18) is arranged in a recirculation line (22) of the line system (12).

4. Fuel cell system with at least one fuel cell unit (26) for electrochemical conversion of a fuel and with at least one fuel cell device according to one of the preceding claims for supplying the fuel cell unit (26) with the fuel.

5. A method for operating a fuel cell device according to one of the preceding claims, wherein in at least one method step the Nernst cell unit (16, 18) detects a process fluid parameter of a fluid located in the line system (12) upstream of the reformer (14).

6. The method according to claim 5, characterized in that a load operation of the fuel cell device is adjusted depending on the process fluid parameter.

7. Method according to claim 5 or 6, characterized in that in at least one method step a fuel feed is adjusted as a function of the process fluid parameter.

8. Method according to one of claims 5 to 7, characterized in that in at least one method step a comparison measurement is carried out in order to determine a further process fluid parameter.

9. Method according to one of claims 5 to 8, characterized in that the process fluid parameter is determined by means of a machine learning process.

10. Use of a Nernst cell unit (16, 18), in particular a lambda probe, of a fuel cell system for monitoring a purging process of the fuel cell system.

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