Fuel battery system

Abstract

To provide a fuel battery system capable of preventing damage to a fuel battery even when a misfire occurs in a combustion part.SOLUTION: A fuel battery system includes: a combustion part 4 for heating a reforming part 2 by a combustion heat; a reforming gas supply part 5 for supplying the reforming gas from the reforming part 4 to a fuel battery 3; an oxygen-containing gas supply part 6 for supplying an oxygen-containing gas to the fuel battery 3; a misfire occurrence detection part 18 for detecting occurrence of misfire in the combustion part 4; a reforming gas heating part 19 capable of heating a reforming gas inlet part 12 in the fuel battery 3; an oxygen-containing gas heating part 20 capable of heating an oxygen-containing gas inlet part 13 in the fuel battery 3; and a control part 21 that controls an operation of the reformed gas heating part 19 and the oxygen-containing gas heating part 20. The control part 21 starts the operation of the reforming gas heating part 19 and the oxygen-containing gas heating part 20 when the misfire occurrence detection part 18 detects the occurrence of misfire in the combustion part 4.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fuel cell system including a reforming section that reforms raw fuel gas to produce reformed gas, a fuel cell that generates electricity using the reformed gas and an oxidant gas, and a combustion section that combusts anode off-gas from the fuel cell and heats the reforming section with the combustion heat. [Background technology]

[0002] Patent document 1 shows a fuel cell system that includes a reforming section (reformer 23) that reforms raw fuel gas to produce reformed gas, a fuel cell (fuel cell stack 21) that generates electricity using the reformed gas and oxidant gas, and a combustion section (combustion section 25) that combusts off-gas from the fuel cell and heats the reforming section with the combustion heat. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-190498 Summary of the Invention [Problem to be solved by the invention]

[0004] In such a fuel cell system, the reformed gas is reformed in the reforming section heated by the combustion section, and therefore has a high temperature, and the oxidant gas is heated by exhaust heat from the combustion section, etc., so that the reformed gas and oxidant gas are supplied to the fuel cell at a relatively high temperature. Then, the fuel cell generates electricity through an electrochemical reaction between the supplied relatively high-temperature reformed gas and oxidant gas, and the entire fuel cell is maintained at a relatively high temperature.

[0005] However, if the combustion section misfires, the reformed gas or oxidant gas is supplied to the fuel cell in an insufficiently heated state, and the temperature begins to drop near the reformed gas inlet port where the reformed gas is supplied and the oxidant gas inlet port where the oxidant gas is supplied. This creates a large temperature difference within the fuel cell, which can lead to damage to the fuel cell, such as cracking of the ceramic parts inside the fuel cell due to thermal stress caused by this temperature difference. In particular, in the compact fuel cells developed in recent years, which have a small thermal capacity, a large temperature difference occurs in the event of a misfire, making fuel cell damage a problem.

[0006] In view of this situation, a main object of the present invention is to provide a fuel cell system that can prevent damage to the fuel cell even if a misfire occurs in the combustion section. [Means for solving the problem]

[0007] A first characteristic configuration of the present invention is a reforming unit that reforms a raw fuel gas to generate a reformed gas; a fuel cell that generates electricity using the reformed gas and an oxidant gas; a combustion unit that combusts anode off-gas from the fuel cell and heats the reforming unit with combustion heat; a reformed gas supply unit that supplies the reformed gas from the reforming unit to the fuel cell; an oxidant gas supply unit that supplies the oxidant gas to the fuel cell; a misfire detection unit that detects the occurrence of a misfire in the combustion unit; a reformed gas heating unit capable of heating a reformed gas inlet of the fuel cell to which the reformed gas is supplied; an oxidant gas heating unit capable of heating an oxidant gas inlet port of the fuel cell to which the oxidant gas is supplied; a control unit for controlling the operation of the reformed gas heating unit and the oxidant gas heating unit, The control unit starts operation of the reformed gas heating unit and the oxidant gas heating unit when the misfire detection unit detects the occurrence of a misfire in the combustion unit.

[0008] According to this configuration, when a misfire occurs in the combustion section, the reformed gas is heated by the reformed gas heating section at the reformed gas inlet of the fuel cell, and the oxidant gas is heated by the reformed gas heating section at the oxidant gas inlet of the fuel cell, so that the temperatures of the reformed gas and oxidant gas supplied to the fuel cell can be increased. Therefore, even when a misfire occurs in the combustion section, the reformed gas and oxidant gas can be supplied to the fuel cell at relatively high temperatures, and temperature differences within the fuel cell can be suppressed, preventing damage to the fuel cell.

[0009] A second characteristic configuration of the present invention includes a flame detection unit that detects the presence or absence of a flame in the combustion unit, The misfire detection unit detects the occurrence of a misfire in the combustion unit based on the detection result of the flame detection unit.

[0010] According to this configuration, the fire detection unit directly detects the presence or absence of a flame in the combustion unit, and the fire occurrence detection unit detects the occurrence of a misfire in the combustion unit based on the detection result of the fire detection unit, making it easier to appropriately detect the occurrence of a misfire in the combustion unit and enabling the occurrence of a misfire to be detected instantaneously. Therefore, approximately simultaneously with the occurrence of a misfire in the combustion unit, the control unit can start operating the reformed gas heating unit and the oxidant gas heating unit to heat the reformed gas and oxidant gas, thereby further suppressing the occurrence of a temperature difference within the fuel cell when a misfire occurs.

[0011] In a third characteristic configuration of the present invention, the reformed gas inlet portion and the oxidant gas inlet portion are disposed adjacent to each other, The reformed gas heating section and the oxidant gas heating section are configured as a common heating section.

[0012] According to this configuration, since the reformed gas inlet port and the oxidant gas inlet port are disposed adjacent to each other, the reformed gas heating section and the oxidant gas heating section for heating them can be rationally configured as a common heating section. By configuring the reformed gas heating section and the oxidant gas heating section as a common heating section, the reformed gas and the oxidant gas heating section can be easily heated simultaneously by simply activating the common heating section in the event of a misfire, and the configuration can be simplified compared to when the reformed gas heating section and the oxidant gas heating section are configured as separate heating sections.

[0013] A fourth characteristic configuration of the present invention is that it includes an anode off-gas reflux section that merges a portion of the anode off-gas from the fuel cell with the reformed gas inlet section of the reformed gas supply section and refluxes it to the fuel cell.

[0014] According to this configuration, a portion of the anode off-gas from the fuel cell is merged into the reformed gas inlet of the reformed gas supply section and mixed with the reformed gas. In the event of a misfire, the reformed gas is heated by mixing with the anode off-gas, and the reformed gas mixed with the anode off-gas can be reliably heated by the pre-reformed gas heating section at the reformed gas inlet. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic overall view of a fuel cell system according to an embodiment of the present invention; [Figure 2] Operation control flow chart [Figure 3] Schematic overall view of a fuel cell system in which the two heating units shown in another embodiment (1) are configured as separate heating units. [Figure 4] Schematic overall view of a fuel cell system not provided with an anode off-gas recirculation unit, shown in another embodiment (2) [Figure 5] Schematic overall view of a fuel cell system shown in another embodiment (2) that does not include an anode off-gas circulation unit and that has two separate heating units. DETAILED DESCRIPTION OF THE INVENTION

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fuel cell system according to an embodiment of the present invention will be described with reference to the accompanying drawings. As shown in Figure 1, the fuel cell system 1 includes a reforming unit 2 that reforms raw fuel gas such as city gas to produce reformed gas, a cell stack 3 (an example of a fuel cell) that generates electricity using the reformed gas supplied as an anode gas and an oxidant gas such as air supplied as a cathode gas, a combustion unit 4 that combusts anode off-gas containing unreacted reformed gas discharged from the cell stack 3 and heats the reforming unit 2 with the combustion heat, an anode gas supply unit 5 (an example of a reformed gas supply unit) that supplies anode gas (reformed gas) from the reforming unit 2 to the cell stack 3, a cathode gas supply unit 6 (an example of an oxidant gas supply unit) that supplies cathode gas (oxidant gas) to the cell stack 3, a reforming water supply unit 7 that supplies reforming water (pure water) to the reforming unit 2, and a raw fuel gas supply unit 10 that supplies raw fuel gas from an anode gas supply source (not shown) to the reforming unit 2.

[0017] The anode gas supply unit 5 is configured to supply the anode gas reformed in the reforming unit 2 to the cell stack 3. The cathode gas supply unit 6 is configured to supply the cell stack 3 with cathode gas from a cathode gas supply source (not shown).

[0018] The reforming section 2 is filled with a reforming catalyst for reforming the raw fuel gas, and is supplied with raw fuel gas from a raw fuel gas supply section 10 and reforming water from a reforming water supply section 7. In the reforming section 2, the supplied reforming water is vaporized into steam using the combustion heat of the combustion section 4, and steam reforming of the raw fuel gas is carried out, thereby producing an anode gas mainly composed of hydrogen.

[0019] The supply side of the cell stack 3 is provided with an anode gas inlet 12 (an example of a reformed gas inlet) to which the anode gas supply unit 5 is connected, and a cathode gas inlet 13 (an example of an oxidant gas inlet) to which the cathode gas supply unit 6 is connected. That is, the anode gas supplied by the anode gas supply unit 5 is supplied to the cell stack 3 from the anode gas inlet 12, and the cathode gas supplied by the cathode gas supply unit 6 is supplied to the cell stack 3 from the cathode gas inlet 13. The anode gas inlet 12 is configured as the downstream end of the anode gas supply unit 5, and the cathode gas inlet 13 is configured as the downstream end of the cathode gas supply unit 6. In the cell stack 3, power is generated by an electrochemical reaction between the anode gas flowing in from the anode gas inlet 12 and the cathode gas flowing in from the cathode gas inlet 13.

[0020] The anode off-gas discharged from the discharge side of the cell stack 3 is supplied to the combustion section 4 by the anode off-gas discharge section 14, and the cathode off-gas discharged from the discharge side of the cell stack 3 is discharged by the cathode off-gas discharge section 15 and supplied to the combustion section 4.

[0021] In the combustion unit 4, the anode off-gas from the cell stack 3 is combusted using the cathode off-gas, and the resulting combustion heat heats the reforming unit 2. The anode gas supplied to the cell stack 3 is heated by the combustion heat in the reforming unit 2 and steam reformed, and thus reaches a relatively high temperature. In addition, the cathode gas supplied to the cell stack 3 is heated by the exhaust heat from the combustion unit 4 while being supplied by the cathode gas supply unit 6, and thus reaches a relatively high temperature. In this way, relatively high-temperature anode gas and cathode gas are supplied to the cell stack 3. In addition, power generation is performed in the cell stack 3 through an electrochemical reaction, and therefore the entire cell stack 3 reaches a relatively high temperature.

[0022] However, when a misfire occurs in the combustion section 4 (hereinafter referred to as "when a misfire occurs"), the anode gas is supplied to the cell stack 3 at a relatively low temperature without being steam reformed in the reforming section 2, and the cathode gas is supplied to the cell stack 3 at a relatively low temperature because it is not sufficiently heated by the exhaust heat of the combustion section 4. Therefore, on the supply side of the cell stack 3 near the anode gas inlet 12 and the cathode gas inlet 13, the temperature drops because relatively low-temperature anode gas and cathode gas are supplied, whereas on the discharge side of the cell stack 3 away from the supply side, a relatively high temperature state is maintained due to the electrochemical reaction caused by the anode gas and cathode gas that were supplied earlier, which raises concerns about a large temperature difference between the supply side and discharge side of the cell stack 3.

[0023] In order to suppress the temperature difference that occurs in the cell stack 3 even when a misfire occurs as described above, the fuel cell system 1 is equipped with a misfire detection unit 18 that detects the occurrence of a misfire in the combustion unit 4, an anode gas heating unit 19 (an example of a reformed gas heating unit) consisting of an electric heater that can heat the anode gas inlet unit 12, a cathode gas heating unit 20 (an example of an oxidant gas heating unit) consisting of an electric heater that can heat the cathode gas inlet unit 13, and a control unit 21 that controls the operation of the anode gas heating unit 19 and the cathode gas heating unit 20.

[0024] To further explain the misfire detection unit 18, the fuel cell system 1 is equipped with a flame rod 23 (an example of a flame detection unit) that detects the presence or absence of a flame in the combustion unit 4, and the misfire detection unit 18 is configured to detect the occurrence of a misfire in the combustion unit 4 based on the detection result of the flame rod 23.

[0025] Then, when a misfire occurs, as detected by the misfire detection unit 18 in the combustion unit 4, the control unit 21 starts operation of the anode gas heating unit 19 and the cathode gas heating unit 20. In this way, the control unit 21 starts operation of the anode gas heating unit 19 and the cathode gas heating unit 20 substantially simultaneously with the occurrence of a misfire, so that the anode gas is supplied to the cell stack 3 in a state heated by the anode gas heating unit 19 at the anode gas inlet unit 12, and the cathode gas is supplied to the cell stack 3 in a state heated by the cathode gas heating unit 20 at the cathode gas inlet unit 13. Therefore, even when a misfire occurs, the anode gas and cathode gas can be supplied to the cell stack 3 in a relatively high temperature state, and the occurrence of a temperature difference within the cell stack 3 is suppressed.

[0026] The anode gas inlet portion 12 and the cathode gas inlet portion 13 are disposed adjacent to each other, and the anode gas heating portion 19 and the cathode gas heating portion 20 are configured by a common heating portion 24 made up of an electric heater. In other words, the anode gas inlet portion 12 and the cathode gas inlet portion 13 are disposed adjacent to each other at a distance that allows them to be heated by the single common heating portion 24, and are configured so that both the anode gas inlet portion 12 and the cathode gas inlet portion 13 are heated by the single common heating portion 24. In this embodiment, the heating portion 24 is configured by a halogen heater that can heat almost simultaneously with operation, and is configured to have a plate-shaped halogen lamp that extends along the direction in which the anode gas inlet portion 12 and the cathode gas inlet portion 13 are aligned and in the direction in which the anode gas inlet portion 12 and the cathode gas inlet portion 13 extend.

[0027] The fuel cell system 1 also includes an anode off-gas return section 25 that extracts a portion of the anode off-gas discharged from the cell stack 3 to the anode off-gas discharge section 14, merges it with the anode gas inlet section 12 of the anode gas supply section 5, and returns it to the cell stack 3. That is, a portion of the anode off-gas discharged from the cell stack 3 that has not been used in the electrochemical reaction (power generation) in the cell stack 3 is branched from the anode off-gas discharge section 14 and supplied to the anode gas inlet section 12 by the anode off-gas return section 25, where it is merged with the anode gas supplied from the reforming section 2. The location where the anode gas and anode off-gas merge is the anode gas inlet section 12, which can be heated by a common heating section 24 (anode gas heating section 19).

[0028] The fuel cell system 1 is also provided with an anode gas temperature sensor 26 that detects the temperature of the anode gas at the anode gas inlet 12 and a cathode gas temperature sensor 27 that detects the temperature of the cathode gas at the cathode gas inlet 13. When the control unit 21 activates the common heating unit 24 in the event of a misfire, the control unit 21 controls the output of the common heating unit 24 based on the detection results of the anode gas temperature sensor 26 and the cathode gas temperature sensor 27 so that the temperature of the anode gas at the anode gas inlet 12 and the temperature of the cathode gas at the cathode gas inlet 13 are maintained at desired temperatures that bring the temperature difference described above within an acceptable range.

[0029] Next, the operation control of the control unit 21 when the fuel cell system 1 is in operation will be described with reference to the flowchart of FIG. When operational control is being performed, the fuel cell system 1 is operating, and anode gas is supplied to the cell stack 3 by the anode gas supply unit 5, cathode gas is supplied to the cell stack 3 by the cathode gas supply unit 6, and reforming water is supplied to the reforming unit 2 by the reforming water supply unit 7. Ignition and combustion occur in the combustion unit 4, and steam reforming of the anode gas is carried out in the reforming unit 2 using the combustion heat from the combustion unit 4, and power is generated in the cell stack 3 by an electrochemical reaction between the anode gas and cathode gas.

[0030] When the misfire occurrence detection unit 18 detects a misfire in the combustion unit 4 while the fuel cell system 1 is operating as described above (#1: Yes), the control unit 21 executes heater-on control (#2) to start the operation of the heating unit 24, thereby increasing the temperature of the anode gas and cathode gas supplied to the cell stack 3, and executes combustion unit ignition control (#3) to re-ignite the misfired combustion unit 4. In this way, when a misfire occurs in the combustion section 4, the anode gas and cathode gas are heated by the heating section 24, thereby increasing the temperatures of the anode gas and cathode gas supplied to the cell stack 3. Therefore, even when a misfire occurs in the combustion section 4, the reformed gas and oxidant gas can be supplied to the fuel cell at a relatively high temperature, and the occurrence of temperature differences within the fuel cell can be suppressed, thereby preventing damage to the fuel cell.

[0031] [Another embodiment] Other embodiments of the present invention will be described below. Note that the configurations of the embodiments described below are not limited to being applied independently, but can also be applied in combination with the configurations of other embodiments.

[0032] (1) In the above embodiment, an example has been described in which the anode gas heating unit 19 and the cathode gas heating unit 20 are configured by a common heating unit 24. However, as shown in FIG. 3, the anode gas heating unit 19 and the cathode gas heating unit 20 may be configured by separate heating units 24.

[0033] (2) In the above embodiment, an example was described in which an anode off-gas reflux section 25 is provided to allow a portion of the anode off-gas from the cell stack 3 to merge with the anode gas inlet section 12. However, if it is not necessary to allow a portion of the anode off-gas to merge with the anode gas inlet section 12, the anode off-gas reflux section 25 may not be provided, as shown in FIG. 4. Even if the anode off-gas reflux section 25 is not provided, the anode gas heating section 19 and the cathode gas heating section 20 may be configured as separate heating sections 24, as shown in FIG. 5.

[0034] (3) In the above embodiment, an example was described in which the heating unit 24 was configured using a plate-shaped halogen lamp. However, the heating unit 24 may be configured as anything other than a halogen lamp, such as a heater using an electric heating wire, and the heating unit 24 may have a shape other than a plate, such as a sheet, lamp, or wire.

[0035] (4) In the above embodiment, the misfire detection unit 18 has been described as being configured to detect the occurrence of a misfire in the combustion unit 4 based on the detection result of the flame rod 23 (flame detection unit). However, the configuration in which the misfire detection unit 18 detects a misfire in the combustion unit 4 may be changed as appropriate. For example, the misfire detection unit 18 may be configured to detect the occurrence of a misfire in the combustion unit 4 based on the temperature detected by the anode gas temperature sensor 26 or the cathode gas temperature sensor 27. Furthermore, the misfire detection unit 18 may be configured to detect the occurrence of a misfire in the combustion unit 4 based on the temperature detected by a combustion unit temperature sensor that detects the temperature of the combustion unit 4. [Explanation of symbols]

[0036] 1. Fuel cell system 2. Modification section 3 Cell stack (fuel cell) 4 Heating section 5. Anode gas supply unit (reformed gas supply unit) 6 Cathode gas supply unit (oxidant gas supply unit) 18 Misfire detection section 19 Anode gas heating unit (reformed gas heating unit) 20 Cathode gas heating unit (oxidant gas heating unit) 21 Control section 23 Flame rod (flame detection part) 24 Heating section 25 Anode off-gas reflux section

Claims

1. a reforming unit that reforms the raw fuel gas to generate a reformed gas; a fuel cell that generates electricity using the reformed gas and an oxidant gas; a combustion unit that combusts anode off-gas from the fuel cell and heats the reforming unit with combustion heat; a reformed gas supply unit that supplies the reformed gas from the reforming unit to the fuel cell; an oxidant gas supply unit that supplies the oxidant gas to the fuel cell; a misfire detection unit that detects the occurrence of a misfire in the combustion unit; a reformed gas heating unit capable of heating a reformed gas inlet of the fuel cell to which the reformed gas is supplied; an oxidant gas heating unit capable of heating an oxidant gas inlet port of the fuel cell to which the oxidant gas is supplied; a control unit for controlling the operation of the reformed gas heating unit and the oxidant gas heating unit, The control unit starts operation of the reformed gas heating unit and the oxidant gas heating unit when the misfire detection unit detects the occurrence of a misfire in the combustion unit.

2. a flame detection unit that detects the presence or absence of a flame in the combustion unit, 2. The fuel cell system according to claim 1, wherein the misfire detection unit detects the occurrence of a misfire in the combustion unit based on the detection result of the flame detection unit.

3. the reformed gas inlet and the oxidant gas inlet are disposed adjacent to each other, 3. The fuel cell system according to claim 1, wherein the reformed gas heating section and the oxidant gas heating section are configured as a common heating section.

4. 3. The fuel cell system according to claim 1, further comprising an anode off-gas recirculation section that recirculates a portion of the anode off-gas from the fuel cell to the reformed gas inlet of the reformed gas supply section.

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