Fuel cell device Prior art

A fuel cell device with at least one fuel cell stack comprising an anode, a cathode and at least one cathode fluid outlet is already known.

Disclosure of the invention

The invention is based on a fuel cell device with at least one fuel cell stack comprising an anode, a cathode and at least one cathode fluid outlet. It is proposed that the fuel cell device comprises at least one reducer element, which is arranged in the cathode fluid outlet and which is provided to adjust flow conditions within a cathode flow path of the fuel cell stack for generating a defined differential pressure between the anode and the cathode. In this context, by a "fuel cell device" is to be understood in particular a functional component, in particular a structural and/or functioning component of a fuel cell system. In this context, a "fuel cell system" is to be understood as a system provided for stationary and/or mobile generation of in particular electrical and/or thermal energy by using at least one fuel cell stack. "Provided" is to be understood in particular as specifically pro- grammed, designed and/or equipped. By an object being provided for a certain function, it is to be understood in particular that the object fulfills and carries out this certain function in at least one application state and/or operation state. In this context, by a "fuel cell stack" is to be understood a unit with at least one fuel cell, which is provided for converting at least a chemical reaction energy of at least one in particular continu- ously supplied fuel gas, in particular hydrogen and/or carbon monoxide, and at least one oxidizing agent, in particular oxygen from air, into electrical and/or thermal energy. The at least one fuel cell may be embodied in particular as a solid oxide fuel cell (SOFC). Preferably, the fuel cell unit comprises a plurality of fuel cells, which are interconnected electrically and/or fluidically. The fuel cell stack is preferably embodied as a planar fuel cell stack. The fuel cell stack comprises an anode and a cathode. During operation of the fuel cell device a fuel gas, in particular hydrogen and/or carbon monoxide, is in particular continuously supplied to the anode of the fuel cell stack. An oxidizing agent, in particular oxygen from air, is in particular continuously supplied to the cathode of the fuel cell stack during operation of the fuel cell device. The fuel cell stack comprises an anode fluid outlet, which is provided for discharging an anode exhaust gas from the fuel cell stack during operation of the fuel cell device. A cathode fluid outlet of the fuel cell stack is provided for discharging a cathode exhaust gas from the fuel cell stack during operation of the fuel cell device. In this context, by a "cathode flow path" is to be understood a flow path along which a fluid, in particular oxygen from air, passes through the cathode of the fuel cell stack during operation of the fuel cell de- vice.

In this context, by a "reducer element" is to be understood an element, which is provided for reducing a gas conductance of at least one fluid line and/or of at least one flow path. In particular, the reducer element is arranged fluidically immediately behind an exhaust outlet of the cathode of the fuel cell stack. In particular, the reducer element is provided for reducing an inside diameter of the cathode fluid outlet of the fuel cell stack at at least one point. In particular, the reducer element may be formed in one piece with the cathode fluid outlet. "In one piece" is to mean, in particular, at least materially connected, e.g. by a soldering process, an adhesive bonding process, an injection process and/or another process deemed expedient by a person skilled in the art, and/or to mean, advantageously, formed in one piece. Preferably, the reducer element consists at least partially of a metallic and/or ceramic material. In particular, the material of the reducer element comprises a low thermal expansion coefficient. Preferably, the reducer element consists at least substantially of a ceramic material. Alternatively, the reducer element may consist of a metal which is at least partially, in particular at an inner diameter of the reducer element, coated with a ceramic material.

By a "defined differential pressure" in particular a specific pressure difference between the anode and the cathode is to be understood, at which a diffusion of fuel gas from the anode to the cathode of the fuel cell stack is at least substantially prevented. By such an implementation a fuel cell device having advantageous operative features can be provided. In particular, a defined differential pressure between the anode and the cathode of the fuel cell stack can be ensured during operation of the fuel cell device by arranging the reducer element in the cathode fluid outlet of the fuel cell stack. Here- by, a pressure driven diffusion of fuel gas from the anode to the cathode of the fuel cell stack can be at least substantially prevented, whereby degradation processes caused by flued gas at the cathode of the fuel cell stack can be avoided.

In particular, the reducer element may comprise a fixed inside diameter. Preferably, the reducer element comprises a variable inside diameter for adjusting the differential pressure between the anode and the cathode. The inside diameter of the reducer element may be adjustable in particular manually, semi-automatically and/or automatically. In particular, the inside diameter of the reducer element may be adjustable by a mechanical and/or electromechanical system. The inside diameter of the reducer element can particularly be reduced and/or enlarged during and/or before operation of the fuel cell device, to archive a defined differential pressure between the anode and the cathode of the fuel cell stack during operation of the fuel cell device. Hereby, a differential pressure between the anode and the cathode of the fuel cell stack can be set to a defined value in an advantageously simple and/or reliable manner.

Furthermore, it is proposed that the flow conditions within the cathode flow path of the fuel cell stack are adjustable depending on at least one operating parameter of the fuel cell stack. For example, the flow conditions within the cathode flow path of the fuel cell stack can be adjusted depending on a composition and/or a quality of the fluidical fuel, a temperature of the fuel cell stack and/or another operating parameter, which has an impact on the optimal differential pressure between the anode and the cathode of the fuel cell stack. Particularly, the flow conditions within the cathode flow path of the fuel cell stack may be adjusted continuously and/or quasi-continuously, depending on at least one operating parameter of the fuel cell stack. In particular, multiple operating parameters may be considered for an adjustment of the flow conditions within the cathode flow path of the fuel cell stack. Preferably, the flow conditions within the cathode flow path of the fuel cell stack are adjustable depending at least on an operating time of the fuel cell stack. In particular, the fuel cell device comprises a monitoring unit which is provided to capture and/or measure at least one operating parameter and/or an operat- ing time of the fuel cell stack. The monitoring unit in particular comprises a sensor unit and/or a time keeping unit. A "sensor unit" is to mean, in this context, in particular a unit which is provided to capture in particular physical and/or chemical properties and/or the material constitution of its surroundings in terms of quality and/or as a measurement in terms of quantity. A "timekeeping unit" is to mean, in this context, in particular a unit which is provided to capture at least one time interval, in particular directly and/or indi- rectly, e.g. by way of an external clock signal. Hereby, a differential pressure between the anode and the cathode of the fuel cell stack can be adapted to changing operating parameters and/or operating time related changes of an operational behavior of the fuel cell stack in an advantageously simple and/or reliable manner. It is further proposed that the fuel cell device comprises at least one control unit, which is provided to adjust the flow conditions within the cathode flow path of the fuel cell stack depending on at least one operating parameter and/or on an operating time of the fuel cell stack. A "control unit" should in particular be understood to mean an electronic unit which comprises at least one computing unit, and preferably at least one memory unit having stored therein an operating program which is intended to be executed by the computing unit. Particularly, the control unit is provided for changing an inside diameter of the reducer element automatically depending on at least one operating parameter and/or on an operating time of the fuel cell stack. The control unit is in particular connected with a monitoring unit which is provided to capture and/or meas- ure at least one operating parameter and/or an operating time of the fuel cell stack.

Alternatively, a monitoring unit which is provided to capture and/or measure at least one operating parameter and/or an operating time of the fuel cell stack may be at least partly integrated in the control unit. Preferably, the fuel cell device comprises a storage unit, which is provided for storing differential pressure parameters to be set depending on at least one operating parameter and/or on an operating time of the fuel cell stack.

Hereby, an advantageously automatic adjustment of a differential pressure between the anode and the cathode of the fuel cell stack can be realized.

It is moreover proposed that the fuel cell device comprises a pressure sensor unit, which is provided for measuring the differential pressure between the anode and the cathode. Particularly, the pressure sensor unit is provided for measuring the differential pressure between the anode and the cathode of the fuel cell stack during an operation of the fuel cell device. For example, the pressure sensor unit may comprise a differential pressure sensor provided for a direct measurement of the differential pressure be- tween the anode and the cathode of the fuel cell stack. Alternatively, the pressure sensor unit may comprise pressure sensors for measuring the pressure in the anode and the cathode of the fuel cell stack separately, whereby the values of the pressure sensors are continuously compared with each other to determine the current differential pressure between the anode and the cathode of the fuel cell stack. Hereby, an advantageous monitoring of a differential pressure between the anode and the cathode of the fuel cell stack can be realized.

Furthermore, a fuel cell system is proposed with at least one fuel cell device according to the invention. Hereby, a fuel cell system having advantageous operative features can be provided. Besides the fuel cell device, the fuel cell system may comprise further components and/or units such as supply pipes for fuel and/or air, flue pipes, heat exchangers, compressors, catalytic converters, compressors, and/or afterburners. Furthermore, the fuel cell system may comprise a desulfurization unit" and/or a reformer unit. In this context, a "desulfurization unit" is to be understood as a unit provided to reduce a volume and/or mole fraction of sulfur compounds in a fluidic fuel, for example natural gas, in particular below a specified threshold value and preferably to remove a volume and/or mole fraction of sulfur compounds in the fuel at least substantially from the fuel, preferably by at least one physical and/or chemical adsorption and/or absorption process. In this context, by a "reformer unit" is to be understood in particular a chemical-technical unit, which is provided for processing a hydrocarbon containing flu- idic fuel, for example a natural gas, in particular for generating a fuel gas, in particular hydrogen, containing gas mixture, in particular by partial oxidation and/or by an auto- thermal reforming and/or preferably by steam reforming.

Furthermore, a method for operating a fuel cell device, which is provided to be operat- ed with a fluidic fuel and which comprises at least one fuel cell stack with an anode, a cathode, at least one anode fluid outlet and at least one cathode fluid outlet, wherein flow conditions within a cathode flow path of the fuel cell stack are adjusted for generating a defined differential pressure between the anode and the cathode. Hereby, a sufficient amount of water can be supplied to the reformer unit even when shutting down the fuel cell unit. Hereby, a defined differential pressure between the anode and the cathode of the fuel cell stack can be ensured during operation of the fuel cell device by arranging the reducer element in the cathode fluid outlet of the fuel cell stack. A pressure driven diffusion of fuel gas from the anode to the cathode of the fuel cell stack can be at least substantially prevented, whereby degradation processes caused by flued gas at the cathode of the fuel cell stack can advantageously be avoided. The fuel cell device according to the invention is herein not to be restricted to the application and implementation described above. In particular, for fulfilling a function herein described, the fuel cell device according to the invention may comprise a number of individual elements, components and units, which differ from the number herein mentioned.

Drawings

Further advantages may be gathered from the following description of the drawing. In the drawing an exemplary embodiment of the invention is shown. The drawing, the description and the claims comprise a plurality of features in combination. The person skilled in the art will expediently also consider the features individually and will bring them together in further purposeful combinations.

The drawing shows:

In fig. 1 a schematic view of a fuel cell system with a fuel cell device comprising a fuel cell stack and a reducer element to adjust a differential pressure between an anode and a cathode of the fuel cell stack.

Description of the exemplary embodiment

Figure 1 shows a schematic view of a fuel cell system 32. The fuel cell system 32 comprises a fuel cell device 10, which is provided to be operated with a fluidic fuel, in particular with natural gas. Alternatively, it is also conceivable to operate the fuel cell device 10 with another hydrocarbon containing in particular gaseous fuel such as biogas. The fuel cell device 10 comprises a fuel cell stack 12. The fuel cell stack 12 is shown here in a simplified manner. The fuel cell stack 12 is preferably embodied as a solid oxide fuel cell stack. The fuel cell stack 12 comprises an anode 14 and a cathode 16. From a fuel supply line 34 the fluidic fuel is fed to the fuel cell system 32. Feed-in of the fluidic fuel can be controlled and/or regulated and/or entirely interrupted by a fuel valve 36. The fuel valve 36 is preferably electro-magnetically actuatable. By means of a fuel compressor 38, a sufficient flow- rate of the fluidic fuel is ensured. Air is fed to a cathode 16 of the fuel cell stack 12 by means of a further compressor 40 or fan. Before entering the cathode 16 the air is preheated by a preheating unit 42. Furthermore, the fuel cell system 32 comprises a desulfurization unit 44. The desulfurization unit 44 is connected downstream of the fuel compressor 38. The desulfurization unit 44 is provided to desulfurize the fluidic fuel. The fuel cell system 32 further comprises a reformer unit 46. The reformer unit 46 is provided for obtaining a hydrogen-rich fuel gas by processing the desulfurized fluidic fuel. Before entering the reformer unit 46, the desul- furized fluidic fuel is preheated by a further preheating unit 60. The hydrogen-rich gas leaving the reformer unit 46 is fed to the anode 14 of the fuel cell stack 12. The fuel cell stack 12 comprises an anode fluid outlet 50, which is provided for discharging an anode exhaust gas from the fuel cell stack 12 during operation of the fuel cell device 10. A cathode fluid outlet 18 of the fuel cell stack 12 is provided for discharging a cathode exhaust gas from the fuel cell stack 12 during operation of the fuel cell device 10. During operation of the fuel cell stack 12 an exhaust gas of the anode 14 and an exhaust gas cathode 16 of the fuel cell stack are fed to a combustion unit 52 via the anode fluid outlet 50 and the cathode fluid outlet 18. In the combustion unit 52 an afterburning of combustible components remaining in the anode exhaust gas is effected. Thermal energy herein released is transferred, for example to a heating water circulation 54 via a heat exchanger 56, to the reformer unit 46 and/or to the preheating units 46, 60. An exhaust gas is discharged via a chimney 58. The fuel cell device 10 comprises at least one reducer element 20, which is arranged in the cathode fluid outlet 18. The reducer element 20 is provided to adjust flow conditions within a cathode flow path 22 of the fuel cell stack 12 for generating a defined differential pressure between the anode 14 and the cathode 16. Along the cathode flow path 22 a fluid, in particular air that contains oxygen, passes through the cathode 16 of the fuel cell stack 12 during operation of the fuel cell device 10. In particular, the reducer element 20 is arranged fluidically immediately behind an exhaust outlet of the cathode 16 of the fuel cell stack 12. In particular, the reducer element 20 may comprise a fixed inside diameter. Preferably, the reducer element 20 comprises a variable inside diameter for adjusting the differential pressure between the anode 14 and the cathode 16. The inside diameter of the reducer element 20 may be adjustable in particular manually, semi-automatically and/or preferably automatically. In particular, the inside diameter of the reducer element 20 may be adjustable by a mechanical and/or electromechanical system. The inside diameter of the reducer element 20 can particularly be reduced and/or enlarged during and/or before operation of the fuel cell device 10 to achieve a defined differential pressure between the anode 14 and the cathode 16 of the fuel cell stack 12 during operation of the fuel cell device 10. Preferably, the reducer element 20 consists at least partly of a metallic and/or ceramic material. In particular, the material of the reducer element 20 comprises an advantageously low thermal expansion coefficient. Preferably, the reducer element 20 consists at least substantially of a ceramic material. Alternatively, the reducer element 20 may consist of a metal which is at least partly, in particular at an inner diameter of the reducer element 20, coated with a ceramic material.

The flow conditions within the cathode flow path 22 of the fuel cell stack 12 are adjustable depending on at least one operating parameter of the fuel cell stack 12, for exam- pie a composition and/or a quality of the fluidical fuel, a temperature of the fuel cell stack 12 and/or another operating parameter, which has an impact on the optimal differential pressure between the anode 14 and the cathode 16 of the fuel cell stack 12. Alternatively or in addition, the flow conditions within the cathode flow path 22 of the fuel cell stack 12 are adjustable depending at least on an operating time of the fuel cell stack 12. Particularly, the flow conditions within the cathode flow path 22 of the fuel cell stack 12 may be adjusted continuously and/or quasi-continuously.

Furthermore, the fuel cell device 10 comprises at least one control unit 26, which is provided to adjust the flow conditions within the cathode flow path 22 of the fuel cell stack 12 depending on at least one operating parameter and/or on an operating time of the fuel cell stack 12. The control unit 26 comprises an integrated monitoring unit 62 which is provided to capture and/or measure at least one operating parameter and/or an operating time of the fuel cell stack 12. In particular, the control unit 26 is provided to adjust the flow conditions within the cathode flow path 22 of the fuel cell stack 12 by changing the inside diameter of the reducer element 20 depending on at least one operating parameter and/or on an operating time of the fuel cell stack 12. Alternatively or in addition, the control unit 26 may be provided to adjust the flow conditions within the cathode flow path 22 of the fuel cell stack 12 by changing a flow rate within the cathode flow path 22, e.g. by changing the power of the compressor 40. Furthermore, the fuel cell device 10 comprises a storage unit 30, which is provided for storing differential pressure parameters to be set depending on at least one operating parameter and/or on an operating time of the fuel cell stack 12. The storage unit 30 is preferably integrated into the control unit 26. The fuel cell device 10 comprises further a pressure sensor unit 28, which is provided for measuring the differential pressure between the anode 14 and the cathode 16. For example, the pressure sensor unit 28 may comprise a differential pressure sensor provided for a direct measurement of the differential pressure be- tween the anode 14 and the cathode 16 of the fuel cell stack 12. Alternatively, the pressure sensor unit 28 may comprise pressure sensors for measuring the pressure in the anode 14 and the cathode 16 of the fuel cell stack 12 separately, whereby the values of the pressure sensors are continuously compared with each other to determine the current differential pressure between the anode 14 and the cathode 16 of the fuel cell stack 12.