Device for determining the hydrogen concentration of exhaust gas in an exhaust line of a fuel cell system and fuel cell system

Abstract

The invention relates to a device (1) for determining the H2 concentration of exhaust gas in an exhaust line (12) of a fuel cell system (100), having a sensor (14) which is arranged in a tube section (2), wherein the tube section has an inflow opening (4) and an outflow opening (6). A mounting element (8) divides the exhaust gas which enters through the inflow opening (4) into a first volume flow which flows through a first tube volume (V1) and at least one further volume flow which flows through at least one further tube volume (V2). A purge line (40) opens into the first tube volume (V1) between the inflow opening (4) and the sensor (14). The sensor (14) measures the H2 concentration of the exhaust gas in the first tube volume (V1).

Description

Technical Field

[0001] This invention relates to an apparatus for determining the hydrogen concentration of exhaust gas in the exhaust pipe of a fuel cell system.

[0002] Furthermore, the present invention relates to a fuel cell system. Background Technology

[0003] Hydrogen-based fuel cells are considered a future mobility solution because they emit only water as exhaust gas and offer rapid refueling times. Fuel cells are typically assembled into fuel cell stacks. These stacks require oxygen, primarily obtained from the surrounding air, and fuel, mainly hydrogen, for the chemical reactions.

[0004] Nitrogen gas is known to reach the cathode side of the fuel cell stack via a mass flow of air supplied to the stack through an air path. This nitrogen partially diffuses through the diaphragm of the fuel cell stack to the anode side, displacing hydrogen gas and thus inhibiting normal reaction. To reduce the nitrogen content on the anode side, a valve with a flushing line is routed from the anode side or from the recirculation line to the fuel cell exhaust line to guide the nitrogen-containing anode gas into the surrounding environment. A hydrogen sensor is installed in the exhaust line to check the hydrogen content.

[0005] Furthermore, it is known that hydrogen gas reaches the cathode side from the anode side. This hydrogen gas undergoes partial catalytic combustion and also partially enters the cathode exhaust gas along with the enriched cathode air. Summary of the Invention

[0006] The apparatus according to the invention for determining the hydrogen concentration of exhaust gas in the exhaust pipe of a fuel cell system has the advantage of enabling more accurate determination of the hydrogen content in the exhaust pipe. This is important so that measures can be taken, if necessary, to avoid excessive hydrogen concentration and thus avoid explosive mixtures.

[0007] Without the device according to the invention, there is a risk that the sensor may detect too low or too high a hydrogen concentration in the exhaust gas, because the measurement accuracy of the measuring device decreases disproportionately when measuring low concentrations.

[0008] Furthermore, with the aid of the device according to the invention, the introduction of hydrogen from the anode can be better distinguished from the particularly low concentration from the cathode. Therefore, for example, an increase in this value can be used to infer the porosity in the diaphragm.

[0009] From an economic perspective, with the same measurement accuracy, the device according to the invention can reduce the accuracy requirements of the sensor, thereby saving costs.

[0010] Furthermore, the device according to the invention also protects the sensor from liquid water, which is advantageous for the reliability and lifespan of the sensor.

[0011] One possibility for counteracting excessively high hydrogen concentrations is to interrupt the hydrogen supply from the anode side through scavenging and venting. Another possibility is to selectively increase the air mass flow in the exhaust pipe, which can be directed directly from the air path into the exhaust pipe via a bypass connection. Yet another possibility lies in the catalytic combustion of hydrogen.

[0012] Advantageous configurations and extensions of an apparatus according to the invention for determining the hydrogen concentration of exhaust gas in a fuel cell system and its exhaust pipe are given below.

[0013] Advantageously, the pipe section has a connector for purging the pipeline, through which the purging gas is guided into the first volume, allowing for high-precision determination of the hydrogen concentration in the purging gas.

[0014] To ensure that the purging gas from the purging line mixes as evenly as possible with the exhaust gas from the exhaust line, it is advantageous to arrange an eddy current element between the connector and the sensor.

[0015] Advantageously, the mounting element consists of at least one rectangular plate, as this is a simple and low-cost solution for targeted flow guidance from the sensor.

[0016] Advantageously, the mounting element is constructed as a tube element, because with this shape of the mounting element, it is easier to achieve measurements at the center of the tube section.

[0017] Advantageously, the pipe components are secured within the pipe section via connectors and / or sensor brackets, saving costs because no additional brackets are required.

[0018] Depending on the local flow relationship, this can be achieved by mounting elements, whereby the sensor can be fixed to the outer wall of the pipe section or to the mounting element as needed. Attached Figure Description

[0019] The apparatus according to the invention and the fuel cell system according to the invention are described in more detail below with reference to the accompanying drawings. The drawings schematically illustrate: Figure 1 A schematic topology diagram of a fuel cell system according to the first embodiment of the present invention. Figure 2 : A schematic diagram of a device used to determine the H2 concentration of fluid in the exhaust pipe of a fuel cell system. Figure 3 A schematic topology diagram of a fuel cell system according to a second embodiment of the present invention. Figures 4a-4c A schematic diagram of an apparatus for determining the H2 concentration of fluid in the exhaust pipe of a fuel cell system with different mounting elements, and Figures 5a-5b : A schematic diagram of a device for determining the H2 concentration of a fluid in the exhaust pipe of a fuel cell system having mounting elements configured as tubes. Detailed Implementation

[0020] exist Figure 1 The diagram shows a schematic topology of a fuel cell system 100 according to a first embodiment, which has at least one fuel cell stack 101. The at least one fuel cell stack 101 has an air path 10, an exhaust path 12, and a fuel path 20. The at least one fuel cell stack 101 can be used in mobile applications with high power requirements, such as in heavy-duty vehicles, or in stationary applications, such as in generators.

[0021] Air path 10 serves as an air supply line to supply ambient air to fuel cell stack 101 via inlet 16. Components necessary for operating fuel cell stack 101 are arranged in air path 10. An air compressor 11 and / or a compression unit 11 are arranged in air path 10, which compresses or draws in air according to the various operating conditions of fuel cell stack 101. Downstream of air compressor 11 and / or compression unit 11, a humidification unit 15 may be provided, which enriches the air in air path 10 with a high liquid concentration.

[0022] Other components, such as filters and / or heat exchangers and / or valves, may also be installed within the air path 10. Oxygen-containing air is supplied to the fuel cell stack 101 via the air path 10.

[0023] In addition, the fuel cell system 100 includes an exhaust duct 12 in which water and other components of the air from the air path 10 are transported to the surrounding environment via an outlet 18 after passing through the fuel cell stack 101. The exhaust gas from the exhaust duct 12 may also contain hydrogen (H2) because some of the hydrogen can diffuse through the membrane of the fuel cell stack 101.

[0024] The fuel cell system 100 may also include a cooling circuit configured to cool the fuel cell stack 101. The cooling circuit... Figure 1 It is not shown in the figure because it is not part of the present invention.

[0025] A high-pressure tank 21 and a shut-off valve 22 are located at the inlet of fuel line 20. Other components may be arranged in fuel line 20 to supply fuel to fuel cell stack 101 as needed.

[0026] To ensure a consistent and adequate fuel supply to the fuel cell stack 101, it is necessary to superstoichiometrically measure the fuel via fuel line 20. Excess fuel, along with a certain amount of water and nitrogen (which diffuse through the cell membrane to the anode side), is drawn back into recirculation line 50 and mixed with the fuel measure from fuel line 20.

[0027] Various components can be installed to drive the recirculation loop 50, such as a beam pump 51 or a blower 52 that operates with quantified fuel. A combination of the beam pump 51 and the blower 52 is also feasible.

[0028] Because the amount of water and nitrogen continues to increase over time, the recirculation loop 50 must be flushed from time to time to prevent the performance of the fuel cell stack 101 from being reduced due to excessive nitrogen concentration in the fuel line 20.

[0029] A purging line 40 is arranged between the recirculation line 50 and the exhaust line 12, so that the gas mixture from the recirculation line 50 can flow into the exhaust line 12.

[0030] A purge valve 44 may be arranged in the purge line 40, which can open and close the connection between the circulation line 50 and the exhaust line 12. The purge valve 44 is typically open for a short time, allowing the gas mixture to be guided through the purge line 40 into the exhaust line 12.

[0031] According to one embodiment of the present invention, a device 1 for determining the H2 concentration is arranged in the exhaust pipe 12.

[0032] Figure 2 A schematic diagram of an apparatus 1 for determining H2 concentration is shown. Apparatus 1 consists of a pipe section 2 having a sensor 14 that measures the hydrogen concentration in a fluid. The pipe section 2 has an inlet opening 4 and an outlet opening 6. Furthermore, a mounting element 8 is arranged in the pipe section 2, which divides the exhaust gas entering through the inlet opening 4 into a first volumetric flow flowing through a first pipe volume V1 and a second volumetric flow flowing through a second pipe volume V2.

[0033] In another embodiment of the invention, pipe section 2 may have a connector 41 for purging conduit 40. Connector 41 establishes a connection between the first volume V1 and the purging conduit 40. Purging gas from the purging conduit 40 is guided into the first volume V1 through connector 41.

[0034] The connector 41 for the purging line 40 is arranged between the inlet opening 4 and the sensor 14, such that the sensor 14 measures not only the H2 concentration from the exhaust gas line 12 but also the H2 concentration from the purging line 40 during measurement.

[0035] Figure 1A fuel cell system 100 with a device without a connector 41 is shown, wherein a purging line 40 extends into an exhaust line 12 in the flow direction prior to the device 1.

[0036] exist Figure 3 The diagram shows a fuel cell system 100 with a device 1 having a connector 41. Here, the purging line 40 is connected to the connector 41, so that purging gas can flow directly from the purging line 40 through the connector 41 into the first volume V1 of the pipe section 2.

[0037] In order to achieve the best possible mixing of exhaust gas from exhaust pipe 12 and purging gas from purging pipe 40, an eddy current element can be arranged in pipe volume V1 between connector 41 and sensor 14.

[0038] Figure 4 shows cross-sections of three devices 1 with different mounting elements 4, each of which is composed of at least one rectangular plate.

[0039] exist Figure 4a In the section 2, the rectangular plate is arranged parallel to the center vertical line (represented by the dashed line), so as to form a smaller first pipe volume V1 and a larger second pipe volume V2.

[0040] exist Figure 4b In the section 2, three rectangular plates are arranged parallel to the center vertical line (represented by dashed lines) to form four pipe volumes V1, V2, V3 and V4.

[0041] exist Figure 4c In the section 2, three rectangular plates are arranged parallel to the center vertical line (represented by dashed lines), and two rectangular plates are arranged perpendicular to the center vertical line, thus forming twelve pipe volumes V1, V2, V3, ..., V12.

[0042] Figure 5 shows one embodiment of the device 1, wherein the mounting element 8 is constituted by a tubular element. Figure 5a The diagram shows a cross-section of device 1, wherein a cross-sectional plane perpendicular to the main flow direction is selected. Figure 5b The diagram shows the cross-section of device 1, with the cross-sectional plane selected to be parallel to the main flow direction.

[0043] In the illustrated embodiment, mounting element 8 is a circular tubular element arranged within the tubular volume such that two concentric circles are formed in the cross-sectional plane. The first tubular volume V1 can be selected inside the tubular element 8, as shown in the figure.

[0044] The pipe element 8 does not have direct contact with the outer wall 3 of the pipe section (2) and is fixed in the pipe section 2 by the bracket of the connector 41 and / or the sensor 14.

[0045] Depending on the selection of the first tube volume V1, the sensor 14 can be fixed to the outer wall 3 of the tube section 2 or to the mounting element 8. The sensor can also be fixed to the outer wall 3 so that the measurement can be performed in the volume V2.

Claims

1. A device (1) for determining the hydrogen concentration of exhaust gas in an exhaust pipe (12) of a fuel cell system (100), comprising a sensor (14) arranged in a pipe section (2), wherein, The pipe section (2) has an inlet opening (4) and an outlet opening (6), characterized in that the exhaust gas entering through the inlet opening (4) is divided by an installation element (8) into a first volume flow through a first pipe volume (V1) and at least one additional volume flow through at least one additional pipe volume (V2), wherein the sensor (14) measures the hydrogen concentration of the exhaust gas in the first pipe volume (V1), wherein the pipe section (2) has a connector (41) for a purging pipe (40), wherein the purging gas of the purging pipe (40) is guided into the first pipe volume (V1) through the connector (41), wherein the connector (41) for the purging pipe (40) is arranged between the inlet opening (4) and the sensor (14).

2. The apparatus (1) according to claim 1, characterized in that, An eddy current element is arranged between the connector (41) and the sensor (14).

3. The apparatus (1) according to claim 1 or 2, characterized in that, The mounting element (8) is composed of at least one rectangular plate.

4. The apparatus (1) according to claim 1 or 2, characterized in that, The mounting element (8) is a tubular element.

5. The apparatus (1) according to claim 4, characterized in that, The tube element does not have direct contact with the outer wall (3) of the tube section (2) and is fixed in the tube section (2) by the connector (41) and / or the bracket of the sensor (14).

6. The apparatus (1) according to any one of claims 1, 2 and 5, characterized in that, The sensor (14) is fixed on the outer wall (3) of the pipe section (2) or on the mounting element (8).

7. A fuel cell system (100) having at least one fuel cell stack (101), an air path (10), an exhaust line (12), a fuel line (20), and a recirculation line (50), wherein, Air from the surrounding environment reaches the fuel cell via the air path (10), wherein fuel is transported to the fuel cell stack (101) via the fuel line (20), wherein the recirculation line (50) has a purging line (40), characterized in that a device (1) according to any one of claims 1 to 6 is arranged in the exhaust line (12).

8. The fuel cell system (100) according to claim 7, characterized in that, The cleaning conduit (40) is connected to the connector (41) of the device (1).

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