Fuel Cell Systems

Abstract

To provide a fuel cell system capable of preventing a reverse flow of cathode off-gas to an anode discharge passage.SOLUTION: A fuel cell system 1 is capable of being driven in switched power generation operation or electrolysis operation. The fuel cell system 1 includes: a fuel cell 2 including an anode flow passage 21 and a cathode flow passage 22; a combustor 3 for mixing and combusting anode off-gas discharged from the anode flow passage 21 and cathode off-gas discharged from the cathode flow passage 22; an anode discharge passage 13 that connects the anode flow passage 21 with the combustor 3; a cathode discharge passage 14 that connects the cathode flow passage 22 with the combustor 3; a recovery flow passage 4 for recovering the anode off-gas containing hydrogen; and a reverse flow prevention mechanism 5 for preventing the cathode off-gas from reversely flowing in the anode exhaust discharge passage 13.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fuel cell system. [Background technology]

[0002] Patent Document 1 discloses a fuel cell system that can switch between power generation and electrolysis. That is, the power generation operation in which hydrogen reacts with oxygen to generate power, and the electrolysis operation in which water is electrolyzed to produce hydrogen, can be performed by the same fuel cell. This fuel cell system has a combustor that mixes and combusts anode off-gas and cathode off-gas. During electrolysis, the anode off-gas contains a large amount of hydrogen. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-537782 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above fuel cell system, there is a concern that if the pressure in the anode exhaust channel drops during electrolysis, the cathode off-gas may flow back through the anode exhaust channel. Therefore, it is necessary to prevent such backflow and prevent the oxidant gas in the cathode off-gas from reacting with the hydrogen in the anode off-gas.

[0005] The present invention has been made in view of the above problems, and aims to provide a fuel cell system capable of preventing backflow of cathode off-gas into the anode exhaust passage. [Means for solving the problem]

[0006] One aspect of the present invention is a fuel cell system (1) capable of switching between a power generation operation and an electrolysis operation, comprising: a fuel cell (2) having an anode flow path (21) and a cathode flow path (22); a combustor (3) that mixes and combusts the anode off-gas discharged from the anode flow channel and the cathode off-gas discharged from the cathode flow channel; an anode discharge passage (13) connecting the anode flow passage and the combustor; a cathode discharge passage (14) connecting the cathode flow passage and the combustor; a recovery passage (4) for recovering the anode off-gas containing hydrogen; a backflow prevention mechanism (5, 50) for preventing the cathode off-gas from flowing back through the anode exhaust passage; Have death, the backflow prevention mechanism is provided in the anode discharge passage and is configured with a discharge passage valve mechanism (5) that prevents the cathode off-gas from flowing back through the anode discharge passage, The anode discharge passage is provided with at least one of an anode preheater (43) for preheating an anode supply gas to be supplied to the anode flow path and a cathode preheater (42) for preheating a cathode supply gas to be supplied to the cathode flow path, and the discharge passage valve mechanism is provided downstream of the anode preheater or the cathode preheater. , in fuel cell systems. Another aspect of the present invention is a fuel cell system (1) capable of switching between a power generation operation and an electrolysis operation, comprising: a fuel cell (2) having an anode flow path (21) and a cathode flow path (22); a combustor (3) that mixes and combusts the anode off-gas discharged from the anode flow channel and the cathode off-gas discharged from the cathode flow channel; an anode discharge passage (13) connecting the anode flow passage and the combustor; a cathode discharge passage (14) connecting the cathode flow passage and the combustor; a recovery passage (4) for recovering the anode off-gas containing hydrogen; a backflow prevention mechanism (5, 50) for preventing the cathode off-gas from flowing back through the anode exhaust passage; having the backflow prevention mechanism is provided in the anode discharge passage and is configured with a discharge passage valve mechanism (5) that prevents the cathode off-gas from flowing back through the anode discharge passage, In the fuel cell system, the exhaust passage valve mechanism is configured with a check valve. Yet another aspect of the present invention is a fuel cell system (1) capable of switching between a power generation operation and an electrolysis operation, comprising: a fuel cell (2) having an anode flow path (21) and a cathode flow path (22); a combustor (3) that mixes and combusts the anode off-gas discharged from the anode flow channel and the cathode off-gas discharged from the cathode flow channel; an anode discharge passage (13) connecting the anode flow passage and the combustor; a cathode discharge passage (14) connecting the cathode flow passage and the combustor; a recovery passage (4) for recovering the anode off-gas containing hydrogen; a backflow prevention mechanism (5, 50) for preventing the cathode off-gas from flowing back through the anode exhaust passage; having In the fuel cell system, the backflow prevention mechanism has a recovery valve mechanism (50) provided in the recovery flow path, the recovery valve mechanism being configured to open and close in response to the pressure in the anode discharge path. Effect of the Invention

[0007] The fuel cell system includes the backflow prevention mechanism, which can prevent the cathode off-gas from flowing back through the anode exhaust passage, thereby preventing the cathode off-gas from flowing back into the anode exhaust passage.

[0008] As described above, according to the above aspect, it is possible to provide a fuel cell system capable of preventing backflow of cathode off-gas into the anode exhaust passage. In addition, the symbols in parentheses described in the claims and the means for solving the problems indicate a correspondence with the specific means described in the embodiments described below, and do not limit the technical scope of the present invention. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is an explanatory diagram of a fuel cell system according to a first embodiment. [Diagram 2] FIG. 11 is an explanatory diagram of a fuel cell system according to a second embodiment. [Diagram 3] FIG. 11 is an explanatory diagram of a fuel cell system during power generation operation in a third embodiment. [Figure 4] FIG. 11 is an explanatory diagram of a fuel cell system during electrolysis operation in a third embodiment. [Diagram 5] FIG. 11 is an explanatory diagram of a fuel cell system according to a fourth embodiment. [Figure 6] FIG. 13 is an explanatory diagram of a fuel cell system according to a fifth embodiment. [Figure 7] FIG. 13 is an explanatory diagram of a fuel cell system according to a sixth embodiment. [Figure 8] FIG. 23 is an explanatory diagram of a recovery valve mechanism in an open state in the sixth embodiment. [Figure 9] FIG. 23 is an explanatory diagram of a closed state of the recovery valve mechanism in the sixth embodiment. [Figure 10] FIG. 13 is an explanatory diagram of the recovery valve mechanism in an open state in the seventh embodiment. [Figure 11] FIG. 13 is an explanatory diagram of a recovery valve mechanism in a closed state in the seventh embodiment. [Figure 12]FIG. 13 is an explanatory diagram of the recovery valve mechanism in an open state in the eighth embodiment. [Figure 13] FIG. 23 is an explanatory diagram of a closed state of the recovery valve mechanism in the eighth embodiment. [Figure 14] FIG. 23 is an explanatory diagram of the recovery valve mechanism in an open state in the ninth embodiment. [Figure 15] FIG. 23 is an explanatory diagram of a closed state of the recovery valve mechanism in the ninth embodiment. [Figure 16] FIG. 23 is an explanatory diagram of a fuel cell system according to a tenth embodiment. [Figure 17] FIG. 23 is an explanatory diagram of a fuel cell system according to an eleventh embodiment. [Figure 18] FIG. 23 is an explanatory diagram of a fuel cell system according to a twelfth embodiment. [Figure 19] FIG. 23 is an explanatory diagram of a fuel cell system in a thirteenth embodiment. [Figure 20] FIG. 23 is an explanatory diagram of the recovery valve mechanism in an open state in the thirteenth embodiment. [Figure 21] FIG. 23 is an explanatory diagram of the recovery valve mechanism in a closed state in the thirteenth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (Embodiment 1) An embodiment of a fuel cell system will be described with reference to FIG. The fuel cell system 1 of this embodiment is a fuel cell system capable of switching between a power generation operation and an electrolysis operation.

[0011] As shown in FIG. 1, the fuel cell system 1 includes a fuel cell 2, a combustor 3, an anode discharge channel 13, a cathode discharge channel 14, a recovery channel 4, and a discharge channel valve mechanism 5. The fuel cell (2) includes an anode channel 21 and a cathode channel 22. The combustor 3 mixes and combusts anode offgas discharged from the anode channel 21 and cathode offgas discharged from the cathode channel 22. The anode discharge channel 13 connects the anode channel 21 to the combustor 3. The cathode discharge channel 14 connects the cathode channel 22 to the combustor 3. The recovery channel 4 recovers anode offgas containing hydrogen. The discharge channel valve mechanism 5 is one aspect of a backflow prevention mechanism that prevents the cathode offgas from flowing back through the anode discharge channel. The discharge channel valve mechanism 5 is provided in at least one of the anode discharge channel 13 and the cathode discharge channel 14, and prevents the cathode offgas from flowing back through the anode discharge channel 13.

[0012] In this embodiment, the discharge channel valve mechanism 5 is provided in the anode discharge channel 13. In this embodiment, the discharge channel valve mechanism 5 is configured as a check valve. In the following, unless otherwise specified, the discharge channel valve mechanism 5 will be described as a check valve 5. The check valve 5 is provided to prevent backflow from the combustor 3 side to the fuel cell 2 side in the anode discharge channel 13. In other words, the check valve 5 is closed when the pressure on the fuel cell 2 side in the anode discharge channel 13 becomes lower than the pressure on the combustor 3 side.

[0013] The power generation operation is an operation in which electric energy is produced using hydrogen as fuel in the fuel cell 2. The electrolysis operation is an operation in which hydrogen is produced from water vapor using electric energy in the fuel cell 2.

[0014] The recovery passage 4 recovers a portion of the anode off-gas. Hydrogen contained in the recovered anode off-gas is reused in the fuel cell system 1, for example. In this embodiment, the recovery flow path 4 and the anode discharge path 13 are drawn out from the anode flow path 21 and branch off from each other along the way. Here, the common portion of the anode discharge path 13 and the recovery flow path 4, which is connected to the anode flow path 21, is both the anode discharge path 13 and the recovery flow path 4.

[0015] In the fuel cell system 1 of this embodiment, the recovery passage 4 is provided with a recovery control valve 41 that controls the flow of the anode off-gas. The recovery control valve 41 is provided in the recovery passage 4 downstream of the branch point with the anode discharge passage 13. The recovery control valve 41 controls the flow of the anode off-gas to be recovered. The recovery control valve 41 can be configured, for example, so that only opening and closing can be controlled, and only two stages of control can be performed, that is, whether or not the anode off-gas is recovered in the recovery passage 4. Alternatively, the recovery control valve 41 can be configured, for example, so that not only opening and closing, but also increasing and decreasing the flow rate of the anode off-gas in the recovery passage 4 can be configured. The recovery control valve 41 can be configured, for example, with an electromagnetic valve or the like.

[0016] The fuel cell system 1 also has an anode supply path 11 and a cathode supply path 12. The anode supply path 11 is a path through which an anode supply gas supplied to an anode flow path 21 of the fuel cell 2 flows. The cathode supply path 12 is a path through which a cathode supply gas supplied to a cathode flow path 22 of the fuel cell 2 flows.

[0017] A hydrocarbon fuel gas F mainly composed of methane, for example, is introduced into the anode supply passage 11. For example, city gas can be used as the fuel gas F. A steam supply passage 111 is connected to the anode supply passage 11, and steam W is merged with the fuel gas F. A reformer 112 is provided in the anode supply passage 11. In the reformer 112, the fuel gas F is reformed to generate hydrogen. At this time, steam is used to reform the fuel gas. That is, in this embodiment, the reformer 112 generates hydrogen by a steam reforming reaction.

[0018] An oxidant gas A is introduced into the cathode supply passage 12. In this embodiment, the oxidant gas A is air. A cathode preheater 42 is provided between the recovery passage 4 and the cathode supply passage 12. The cathode preheater 42 preheats the cathode supply gas by heat of the anode off-gas. The preheated cathode supply gas (i.e., preheated oxidant gas) is supplied to the cathode flow passage 22 of the fuel cell 2. This supplies heat to the fuel cell 2. That is, during electrolysis operation, the heat of the anode off-gas is transferred to the fuel cell 2 via the oxidant gas, which is the cathode supply gas.

[0019] The fuel cell 2 has an electrolyte disposed between the anode flow path 21 and the cathode flow path 22. In this embodiment, a solid oxide fuel cell (i.e., SOFC) using solid oxide ceramics as the electrolyte can be used as the fuel cell 2. In this case, during electrolysis operation, the fuel cell 2 becomes a solid oxide electrolysis cell (i.e., SOEC).

[0020] In the power generation operation, an anode supply gas containing hydrogen is supplied to the anode flow path 21 of the fuel cell 2, and a cathode supply gas which is an oxidant gas containing oxygen is supplied to the cathode flow path 22. This causes hydrogen and oxygen to react in the electrolyte of the fuel cell 2 to generate electrical energy. Anode off-gas containing surplus hydrogen not used in the reaction in the anode flow path 21 is discharged to the anode exhaust channel 13. Cathode off-gas containing surplus oxygen not used in the reaction in the cathode flow path 22 is discharged to the cathode exhaust channel 14.

[0021] During power generation operation, the recovery control valve 41 in the recovery passage 4 is closed. This allows the anode off-gas to be introduced into the combustor 3 via the anode exhaust passage 13. The cathode off-gas is also introduced into the combustor 3 via the cathode exhaust passage 14. In the combustor 3, the hydrogen in the anode off-gas and the oxygen in the cathode off-gas are mixed and combusted.

[0022] In the electrolysis operation, an anode supply gas containing water vapor is supplied to the anode flow path 21 of the fuel cell 2. The amount of water vapor supplied during the electrolysis operation is greater than the amount of water vapor supplied during the power generation operation. In the electrolysis operation, the anode supply gas also contains a fuel gas containing hydrogen. This makes it possible to maintain the anode flow path 21 of the fuel cell 2 in a reducing atmosphere. In the electrolysis operation, a cathode supply gas, which is an oxidant gas, is supplied to the cathode flow path 22 of the fuel cell 2.

[0023] By supplying power to the electrolyte in the fuel cell 2, water vapor is electrolyzed to generate hydrogen. The electrolytic reaction in the electrolyte in the fuel cell 2 at this time is an endothermic reaction. Therefore, during electrolytic operation, it becomes necessary to supply heat to the electrolyte. However, by supplying a preheated cathode supply gas (i.e., an oxidant gas) to the fuel cell 2 as described below, heat is also supplied to the electrolyte.

[0024] The generated hydrogen is discharged as anode off-gas from the anode flow path 21 to the anode discharge path 13. A portion of this anode off-gas containing hydrogen is recovered via the recovery flow path 4. That is, during electrolysis operation, the recovery control valve 41 is opened so that the anode off-gas is introduced into the recovery flow path 4.

[0025] Then, in the cathode preheater 42, the high-temperature anode off-gas containing hydrogen flowing through the recovery passage 4 exchanges heat with the cathode supply gas (i.e., oxidant gas) flowing through the cathode supply passage 12. That is, the high-temperature anode off-gas containing hydrogen preheats the cathode supply gas. By introducing the preheated cathode supply gas into the fuel cell 2, the temperature of the fuel cell 2 is easily maintained high. As a result, the electrolysis operation, which is the endothermic reaction described above, is carried out efficiently.

[0026] The fuel cell system 1 of this embodiment can be mounted on a vehicle such as a fuel cell vehicle. Switching between power generation operation and electrolysis operation can be achieved by switching the supply of power to the fuel cell 2 and the composition of the anode supply gas (eg, the amount of water vapor contained).

[0027] The fuel cell system 1 is provided with a control device (not shown). The control device controls the operation of each controlled device that constitutes the fuel cell system 1. The control device is composed of a well-known microcomputer including a CPU, ROM, RAM, etc., and its peripheral circuits. The control device can perform switching between the power generation operation and the electrolysis operation, and open / close control of the recovery control valve 41. The control device is configured, for example, within an ECU (that is, an electronic control unit).

[0028] Next, the effects of this embodiment will be described. The fuel cell system 1 has the above-mentioned check valve 5. This makes it possible to prevent the cathode off-gas from flowing back through the anode exhaust channel 13. Therefore, with a simple configuration, it is possible to prevent the cathode off-gas from flowing back into the anode exhaust channel 13.

[0029] That is, for example, during electrolysis operation, as described above, anode off-gas containing hydrogen is recovered through the recovery flow path 4. At this time, the anode off-gas is sucked from the anode discharge path 13 through the recovery flow path 4 by a pump or the like (not shown). Therefore, the pressure in the recovery flow path 4 and the anode discharge path 13 may decrease.

[0030] Here, if the check valve 5 is not provided, there is a concern that if the pressure in the recovery passage 4 and the anode discharge passage 13 drops too much, the cathode offgas in the cathode discharge passage 14 will flow into the anode discharge passage 13 via the combustor 3 and cause a backflow. The cathode offgas contains an oxidant gas (e.g., air). Meanwhile, the recovery passage 4 and the anode discharge passage 13 contain anode offgas containing hydrogen. For this reason, it is necessary to prevent the cathode offgas containing the oxidant gas from flowing back through the anode discharge passage 13.

[0031] The fuel cell system 1 of this embodiment is provided with the above-mentioned check valve 5, and therefore can easily prevent the above-mentioned backflow of the cathode off-gas in the anode discharge channel 13. This makes it possible to prevent the oxidant gas in the cathode off-gas from mixing with the hydrogen in the anode off-gas in the anode discharge channel 13 and the recovery channel 4.

[0032] In order to prevent the backflow of the cathode off-gas in the anode exhaust passage 13, it is also possible to perform control such as constantly increasing the pressure in the anode exhaust passage 13. However, such control tends to reduce the efficiency of hydrogen recovery, making it difficult to improve the efficiency of the entire system. The fuel cell system 1 of this embodiment is advantageous in that it does not require such control.

[0033] Furthermore, in this embodiment, the check valve 5 is provided in the anode discharge passage 13. Therefore, backflow of the cathode off-gas in the anode discharge passage 13 can be prevented easily and reliably.

[0034] Furthermore, in this embodiment, since the discharge channel valve mechanism 5 is configured as a check valve, it is possible to reliably prevent backflow of the cathode off-gas in the anode discharge channel 13 with a simple configuration. That is, in the anode discharge channel 13, the pressure on the fuel cell 2 side is higher than the pressure on the combustor 3 side in normal conditions, and the anode off-gas flows normally to the combustor 3 side. In addition, in the anode discharge channel 13, the pressure on the fuel cell 2 side is lower than the pressure on the combustor 3 side in abnormal conditions, and the check valve 5 blocks the backflow of fluid from the combustor 3 side. Therefore, it is possible to reliably prevent the cathode off-gas from flowing back through the anode discharge channel 13 with a simple configuration.

[0035] As described above, according to this embodiment, it is possible to provide a fuel cell system capable of preventing backflow of cathode off-gas into the anode exhaust passage.

[0036] (Embodiment 2) In this embodiment, as shown in FIG. 2, the check valve 5 is provided downstream of the cathode preheater . In this embodiment as well, a cathode preheater 42 is provided in the anode discharge passage 13. The cathode preheater 42 preheats the cathode supply gas to be supplied to the cathode flow passage 22. A check valve 5 is provided downstream of the cathode preheater 42.

[0037] The anode discharge channel 13 has a common channel that is shared with the recovery channel 4. A cathode preheater 42 is provided in this common channel. The check valve 5 is disposed downstream of the branch point of the anode discharge channel 13 with the recovery channel 4. That is, in this embodiment, the check valve 5 is provided in the anode discharge channel 13 on the downstream side where it branches off from the recovery channel 4, rather than in the common channel.

[0038] Furthermore, a flow rate adjustment valve 135 is provided in the anode discharge path 13 downstream of the branch point with the recovery path 4. In this embodiment, the flow rate adjustment valve 135 is provided upstream of the check valve 5. The flow rate adjustment valve 135 can adjust the flow rate of the anode off-gas in the anode discharge path 13. This makes it possible to adjust the flow rate of the anode off-gas to the combustor 3 in a normal state where the pressure on the fuel cell 2 side is higher than that on the combustor 3 side.

[0039] The recovery control valve 41 is also provided in the recovery flow path 4 downstream of the cathode preheater 42. The recovery control valve 41 is also provided in the recovery flow path 4 downstream of the branch point with the anode discharge path 13.

[0040] The rest is the same as in embodiment 1. Note that, among the symbols used in embodiment 2 and onwards, the same symbols used in the previous embodiments represent the same components, etc. as in the previous embodiments, unless otherwise specified.

[0041] In this embodiment, the check valve 5 is provided at a position in the anode discharge channel 13 where the anode off-gas flows after heat is applied to the oxidant gas in the cathode supply channel 12. That is, the check valve 5 can be provided at a position in the anode discharge channel 13 where the temperature is less likely to become high. This makes it possible to use a check valve 5 with a relatively low heat resistance. As a result, an inexpensive fuel cell system 1 can be obtained.

[0042] Furthermore, the anode discharge channel 13 has a common flow path with the recovery flow path 4, and a cathode preheater 42 is provided in the common flow path. The check valve 5 is disposed downstream of the branch point of the anode discharge channel 13 with the recovery flow path 4. This simplifies the piping configuration of the fuel cell system 1 and effectively prevents backflow of the cathode off-gas in the anode discharge channel 13.

[0043] The recovery control valve 41 is also provided downstream of the cathode preheater 42 in the recovery flow path 4. This means that the recovery control valve 41 is provided at a position in the recovery flow path 4 through which the anode off-gas flows after heat has been applied to the oxidant gas in the cathode supply path 12. In other words, the recovery control valve 41 can be provided at a position in the recovery flow path 4 where the temperature is less likely to become high. This makes it possible to use a recovery control valve 41 with a relatively low heat resistance temperature. As a result, a less expensive fuel cell system 1 can be obtained. In addition, the same effects as those of the first embodiment are achieved.

[0044] (Embodiment 3) As shown in Figs. 3 and 4, this embodiment is a fuel cell system 1 that is based on the configuration of the second embodiment and is further embodied. In this embodiment, in addition to the reformer 112, a desulfurizer 113, an evaporator 114, and a circulation device 115 are provided in the anode supply path 11. The desulfurizer 113, the evaporator 114, and the circulation device 115 are provided in the anode supply path 11 upstream of the reformer 112 in this order from the upstream side.

[0045] The fuel cell system 1 of this embodiment also has a first circulation path 131 and a second circulation path 132 described below. The first circulation path 131 circulates the anode off-gas from the downstream side of the anode flow path 21 of the fuel cell 2 to the circulation device 115. The second circulation path 132 circulates the anode supply gas from the downstream side of the reformer 112 and the upstream side of the fuel cell 2 in the anode supply path 11 to the upstream side of the circulation device 115.

[0046] In this embodiment, the circulation device 115 can be configured as an ejector. In the following, the circulation device 115 will be described as the ejector 115. The ejector 115 uses the fuel gas flowing through the anode supply path 11 as a driving flow to draw in the anode off-gas from the first circulation path 131. The ejector 115 has a nozzle portion 115a, a suction portion 115b, and a discharge portion 115c. The nozzle portion 115a injects the fuel gas introduced from the upstream side of the anode supply path 11 as a driving flow. The suction portion 115b draws in the anode off-gas from the first circulation path 131 as a suction flow by the driving flow injected from the nozzle portion 115a. The discharge portion 115c discharges a mixed flow obtained by mixing the driving flow and the suction flow to the downstream side of the anode supply path 11.

[0047] The desulfurizer 113 removes sulfur contained in city gas or the like as the fuel gas F. In this embodiment, the desulfurizer 113 may be a hydrodesulfurizer that removes sulfur by using hydrogen. In this embodiment, the second circulation path 132 is configured to circulate the fuel gas from the anode supply path 11 between the reformer 112 and the fuel cell 2 to the anode supply path 11 upstream of the desulfurizer 113. Therefore, the gas circulated by the second circulation path 132 is a fuel gas that contains a large amount of hydrogen. Therefore, the amount of hydrogen introduced into the desulfurizer 113 can be increased, and effective desulfurization can be performed.

[0048] The evaporator 114 is also connected to a water vapor supply passage 111. In the evaporator 114, water vapor W and fuel gas F are mixed and heated to generate a mixed gas. The fuel gas mixed with water vapor in the evaporator 114 is introduced into the ejector 115 as a driving flow. Then, as described above, the fuel gas mixed with the anode off-gas in the ejector 115 is discharged from the ejector 115 and introduced into the reformer 112. The anode supply gas, which is the fuel gas containing hydrogen and reformed in the reformer 112, is introduced into the anode flow path 21 of the fuel cell 2.

[0049] In this embodiment, a common flow path of the anode discharge channel 13, the first circulation channel 131, and the recovery channel 4 is connected to the downstream side of the anode channel 21 of the fuel cell 2. The first circulation channel 131 branches off from this common flow path. That is, at branch point B1, the common flow path of the anode discharge channel 13 and the recovery channel 4 and the first circulation channel 131 branch off. The common flow path of the anode discharge channel 13 and the recovery channel 4 branches off into the anode discharge channel 13 and the recovery channel 4 at branch point B2 further downstream.

[0050] That is, the anode discharge channel 13 has a portion common to the recovery flow path 4 and the first circulation channel 131, a portion common to the recovery flow path 4, and a portion branched off from the recovery flow path 4. The recovery flow path 4 exchanges heat with the cathode supply gas (i.e., the oxidant gas) in the cathode preheater 42 and then is recovered. In this embodiment, the recovery control valve 41 is provided in the recovery flow path 4 downstream of the cathode preheater 42. The anode discharge channel 13 and the recovery flow path 4 branch off from each other downstream of the cathode preheater 42.

[0051] A check valve 5 is provided in the anode discharge channel 13 at a portion where it branches off from the recovery channel 4. In addition, a flow rate adjustment valve 135 is provided in the anode discharge channel 13 at a portion where it branches off from the recovery channel 4.

[0052] The fuel cell system 1 of this embodiment also has a bypass passage 116 that merges with the anode supply passage 11 so as to bypass the water vapor supply passage 111 and the evaporator 114. In this embodiment, the downstream end of the bypass passage 116 is connected to the anode supply passage 11 between the ejector 115 and the reformer 112. The bypass passage 116 is provided with a bypass control valve 117 that controls the flow of water vapor passing through the bypass passage 116.

[0053] Similarly to the recovery control valve 41, the bypass control valve 117 can be configured, for example, so that it can only be controlled to open and close, and can be controlled in only two stages of whether or not water vapor is passed through the bypass passage 116. Alternatively, the bypass control valve 117 can be configured, for example, not only to open and close, but also to increase and decrease the flow rate of water vapor in the bypass passage 116. The bypass control valve 117 can be configured, for example, by a solenoid valve or the like.

[0054] On the other hand, in addition to the cathode preheater 42, a front-stage preheater 122 and a rear-stage preheater 123 are provided in the cathode supply path 12. The front-stage preheater 122 is provided upstream of the cathode preheater 42 in the cathode supply path 12. The rear-stage preheater 123 is provided downstream of the cathode preheater 42 in the cathode supply path 12.

[0055] The pre-preheater 122 is configured to preheat the cathode supply gas (i.e., oxidant gas) in the cathode supply passage 12 by the heat of the combustion gas discharged from the combustor 3. The combustion gas before being introduced into the pre-preheater 122 imparts heat to the reformer 112 in the combustion catalyst 133 that is in thermal contact with the reformer 112. The combustion gas that has passed through the pre-preheater 122 imparts heat to the fuel gas in the evaporator 114, and is then discharged.

[0056] The rear preheater 123 is configured to receive heat from the warm-up combustor 123a and preheat the cathode supply gas (i.e., oxidant gas) of the cathode supply passage 12. The warm-up combustor 123a mixes and combusts a fuel gas F1 and an oxidant gas A1 supplied from the outside. The exhaust gas from the warm-up combustor 123a is introduced into the combustor 3 via the cathode exhaust passage 14.

[0057] In the fuel cell system 1 of this embodiment, when power generation is performed, the recovery control valve 41 and the bypass control valve 117 are closed as shown in FIG.

[0058] In this state, in the anode supply passage 11, the fuel gas F is introduced into the reformer 112 via the desulfurizer 113, the evaporator 114, and the ejector 115. In the evaporator 114, the fuel gas F is mixed with the water vapor supplied via the water vapor supply passage 111 and evaporated to become a mixed gas with the water vapor, which is sent to the reformer 112 via the ejector 115. The hydrogen-containing fuel gas reformed in the reformer 112 is supplied to the anode flow path 21 of the fuel cell 2 as an anode supply gas.

[0059] Meanwhile, in the cathode supply channel 12, the oxidant gas A is supplied to the cathode flow path 22 of the fuel cell 2 via the front-stage preheater 122, the cathode preheater 42, and the rear-stage preheater 123. As a result, in the fuel cell 2, hydrogen in the fuel gas and oxygen in the oxidant gas are reacted with each other to generate electricity, and electric power is obtained.

[0060] Furthermore, the anode offgas discharged from the anode flow path 21 and the cathode offgas discharged from the cathode flow path 22 are mixed and combusted in the combustor 3. Here, the anode offgas is guided to the combustor 3 through the anode discharge path 13, which includes a common path with the first circulation path 131 and the recovery flow path 4, and a common path with the recovery flow path 4. During this time, the anode offgas passes through the cathode preheater 42, the flow rate adjustment valve 135, and the check valve 5. The anode offgas imparts heat to the oxidant gas in the cathode preheater 42.

[0061] Furthermore, the anode off-gas is circulated from the anode flow passage 21 of the fuel cell 2 to the ejector 115 via the first circulation path 131 and merges with the anode supply gas before reforming. In this embodiment, the recovery control valve 41 is closed during power generation operation.

[0062] Furthermore, the reformed fuel gas circulates from between the reformer 112 and the fuel cell 2 in the anode supply passage 11 to the upstream side of the desulfurizer 113 through the second circulation passage 132. Furthermore, in this embodiment, the bypass control valve 117 is closed during power generation operation. Therefore, water vapor does not bypass the evaporator 114 through the bypass passage 116.

[0063] In the fuel cell system 1 of this embodiment, when performing electrolysis, the recovery control valve 41 and the bypass control valve 117 are opened as shown in FIG.

[0064] In this state, in the cathode supply channel 12 , the oxidant gas A is supplied to the cathode flow passage 22 of the fuel cell 2 via the pre-heater 122 , the cathode pre-heater 42 and the post-heater 123 .

[0065] In the anode supply channel 11, water vapor W and fuel gas F are supplied to the anode flow channel 21 of the fuel cell 2. The fuel gas is supplied together with water vapor in order to create a reducing atmosphere in the anode flow channel 21. The water vapor passes through the bypass channel 116 and merges with the anode supply channel 11 upstream of the reformer 112. The amount of water vapor supplied during electrolysis is greater than the amount of water vapor supplied during power generation. Therefore, during electrolysis, the bypass control valve 117 is opened as described above, and the water vapor is passed through the bypass channel 116 to bypass the evaporator 114 and merges with the anode supply channel 11. The water vapor is preheated in the reformer 112 and supplied to the fuel cell 2.

[0066] During electrolysis, power is supplied to the fuel cell 2. As a result, the hydrogen-containing fuel gas introduced into the anode flow path 21 is electrolyzed to generate hydrogen. At least a portion of the generated hydrogen is recovered via the recovery flow path 4 in a state contained in the anode off-gas. That is, during electrolysis, the recovery control valve 41 is opened. As a result, the hydrogen-containing anode off-gas passes through the recovery control valve 41 and is recovered via the recovery flow path 4.

[0067] During electrolysis, the flow rate control valve 135 in the anode discharge passage 13 can be controlled to be narrower than during power generation. However, the flow rate control valve 135 is opened to a predetermined degree. Therefore, depending on the amount of anode off-gas introduced into the common flow passage of the recovery flow passage 4 and the anode discharge passage 13, some of the anode off-gas passes through the flow rate control valve 135 and the check valve 5 and is introduced into the combustor 3.

[0068] Here, the pressure may fluctuate near the branch point B2 between the recovery passage 4 and the anode discharge passage 13. Even if this pressure temporarily drops, the check valve 5 is provided at a predetermined position in the anode discharge passage 13, so that the cathode off-gas containing oxidant gas is prevented from flowing back from the combustor 3 to the recovery passage 4 side.

[0069] During electrolysis, the oxidant gas is preheated not only in the front-stage preheater 122 and the rear-stage preheater 123, but also in the cathode preheater 42. That is, in the cathode preheater 42, the oxidant gas is preheated by the heat of the anode off-gas containing hydrogen.

[0070] The oxidant gas preheated not only by the front-stage preheater 122 and the rear-stage preheater 123 but also by the cathode preheater 42 is supplied to the fuel cell 2, thereby increasing the temperature of the fuel cell 2. At least a part of this heat is utilized for the endothermic reaction in the electrolysis operation.

[0071] The rear-stage preheater 123 may also be configured not to operate during power generation operation but to operate during electrolysis operation. That is, control may be performed so that the cathode supply gas (i.e., oxidant gas) introduced into the fuel cell 2 is preheated during electrolysis operation when heat is particularly required in the fuel cell 2, and the cathode supply gas is not preheated at other times. The rest is the same as in the first embodiment, and has the same functions and effects.

[0072] (Embodiment 4) As shown in FIG. 5, this embodiment is a fuel cell system 1 in which an anode preheater 43 is provided in the anode discharge passage 13. In the embodiment shown in FIG. The anode preheater 43 is a preheater that preheats the anode supply gas to be supplied to the anode flow path 21. The check valve 5 in the anode discharge path 13 is provided downstream of the anode preheater 43.

[0073] Furthermore, the anode discharge channel 13 has a common flow path with the recovery flow path 4, and an anode preheater 43 is provided in this common flow path. The check valve 5 is disposed downstream of a branch point B2 of the anode discharge channel 13 with the recovery flow path 4. Furthermore, a flow rate adjustment valve 135 is provided in the anode discharge channel 13 at a portion branched off from the recovery flow path 4.

[0074] In this embodiment, the anode preheater 43 is provided in the anode supply path 11 between the reformer 112 and the fuel cell 2. In this embodiment, the recovery control valve 41 is provided in the recovery flow path 4 downstream of the anode preheater 43. In addition, the recovery control valve 41 is disposed in the recovery flow path 4 downstream of a branch point B2 with the anode discharge path 13.

[0075] In this embodiment, the recovery control valve 41 can be closed during power generation operation. Then, during electrolysis operation, the recovery control valve 41 is opened. This allows the anode off-gas containing hydrogen generated in the fuel cell 2 by the electrolysis operation to be recovered via the recovery passage 4.

[0076] Then, in the anode preheater 43, heat from the anode off-gas containing hydrogen is given to the anode supply gas. That is, the water vapor and fuel gas before being supplied to the fuel cell 2 are preheated by the recovered anode off-gas containing hydrogen. The anode supply gas (i.e., water vapor and fuel gas) that has received heat in the anode preheater 43 is introduced into the fuel cell 2. This allows the heat of the anode off-gas containing hydrogen to be given to the electrolyte of the fuel cell 2. At least a part of this heat is utilized for the endothermic reaction during electrolysis operation.

[0077] During electrolysis, the flow rate control valve 135 in the anode discharge passage 13 can be controlled to be narrower than during power generation. However, the flow rate control valve 135 is opened to a predetermined degree. Therefore, depending on the amount of anode off-gas introduced into the common flow passage of the recovery flow passage 4 and the anode discharge passage 13, some of the anode off-gas passes through the flow rate control valve 135 and the check valve 5 and is introduced into the combustor 3.

[0078] Here, the pressure may fluctuate near the branch point B2 between the recovery passage 4 and the anode discharge passage 13. Even if this pressure temporarily drops, the check valve 5 is provided at a predetermined position in the anode discharge passage 13, so that the cathode off-gas containing oxidant gas is prevented from flowing back from the combustor 3 to the recovery passage 4 side.

[0079] The rest is the same as in the third embodiment. In this embodiment, the heat of the anode off-gas containing hydrogen can be provided to the fuel cell 2 via the anode supply gas. In addition, the same effects as those of the third embodiment are achieved.

[0080] (Embodiment 5) In this embodiment, as shown in FIG. 6, the fuel cell system 1 has a discharge passage valve mechanism 5 provided in the cathode discharge passage 14. In the embodiment shown in FIG. In this embodiment, the discharge pipe valve mechanism 5 is not a check valve but an on-off valve that can be opened and closed by control or the like. The discharge pipe valve mechanism 5 may be capable of adjusting the flow rate as well as opening and closing. The discharge pipe valve mechanism 5 may be configured, for example, by a solenoid valve.

[0081] In this embodiment, under normal circumstances, the discharge channel valve mechanism 5 is opened. Then, during electrolysis operation, under abnormal circumstances in which the pressure on the recovery flow path 4 side of the anode discharge channel 13 becomes lower than the pressure on the combustor 3 side, the discharge channel valve mechanism 5 is closed. This makes it possible to prevent the cathode off-gas containing oxygen in the cathode discharge channel 14 from flowing back through the anode discharge channel 13 via the combustor 3.

[0082] Although not shown in the drawings, in this embodiment, for example, pressure sensors are provided in the recovery passage 4, the combustor 3, etc. This makes it possible to detect the above-mentioned pressure abnormality (i.e., a state in which the pressure on the recovery passage 4 side of the anode discharge passage 13 is lower than the pressure on the combustor 3 side). The control device can be configured to close the discharge passage valve mechanism 5 based on this pressure abnormality.

[0083] Other than that, it is the same as in embodiment 1. However, Fig. 6 shows a fuel cell system 1 with a simplified configuration. In this embodiment, too, other than the above differences, it may have the same configuration as embodiment 3 (see Figs. 3 and 4).

[0084] This embodiment also makes it possible to prevent the cathode off-gas from flowing back into the anode exhaust passage 13. In addition, the same effects as those of the first embodiment are achieved.

[0085] (Embodiment 6) In this embodiment, as shown in FIGS. 7 to 9, the recovery valve mechanism 50 is configured to open and close in response to the pressure in the anode discharge passage 13. In the embodiment shown in FIG. That is, in this embodiment, the backflow prevention mechanism has a recovery valve mechanism 50 provided in the recovery flow passage 4. The recovery valve mechanism 50 is configured to open and close in response to the pressure in the anode discharge passage 13. Here, "opening and closing in response to the pressure in the anode discharge passage 13" includes not only the case where it opens and closes in response to the pressure in the anode discharge passage 13 alone, but also the case where it opens and closes in response to the relationship between the pressure in the anode discharge passage 13 and another pressure.

[0086] The recovery valve mechanism 50 is configured to open and close based on the pressure difference between a predetermined first portion 501 in the anode exhaust passage 13 and a pressure in a second portion 502 downstream of the first portion 501. In this embodiment, the second portion 502 is inside the combustor 3. However, the second portion 502 may also be a portion downstream of the first portion 501 in the anode exhaust passage 13. Alternatively, the second portion 502 may be a combustion gas outlet 31 that discharges the combustion gas from the combustor 3.

[0087] 7, the anode discharge channel 13 has a pressure loss section 51 between a first section 501 and a second section 502. The pressure loss section 51 is a section that partially causes a pressure loss of the gas in the anode discharge channel 13. In this embodiment, the pressure loss section 51 is configured by a restriction that locally reduces the cross-sectional area of ​​the flow channel.

[0088] The backflow prevention mechanism further has a first pressure pipe 521 that connects the recovery valve mechanism 50 and the first part 501, and a second pressure pipe 522 that connects the recovery valve mechanism 50 and the second part 502. The backflow prevention mechanism is configured to drive the recovery valve mechanism 50 by the pressure difference between the pressure of the first pressure pipe 521 and the pressure of the second pressure pipe 522.

[0089] 8 and 9, the recovery valve mechanism 50 is connected to the recovery flow passage 4, and is also connected to a first pressure pipe 521 and a second pressure pipe 522. The recovery valve mechanism 50 is configured such that a first piston 541 and a second piston 542, which are connected and fixed to each other, are slidably disposed in a cylinder 53. The first pressure pipe 521 is connected to a first closed space 531 surrounded by the first piston 541 and the cylinder 53. The second pressure pipe 522 is connected to a second closed space 532 surrounded by the second piston 542 and the cylinder 53.

[0090] Further, a communication space 533 that communicates the upstream side and downstream side of the recovery passageway 4 is provided within the cylinder 53. As shown in Fig. 8, when the first piston 541 and the second piston 542 are arranged on the second closed space 532 side, the communication space 533 is opened. As shown in Fig. 9, when the first piston 541 and the second piston 542 are arranged on the first closed space 531 side, the communication space 533 is closed.

[0091] 8, when the pressure in the first pressure pipe 521 is higher than the pressure in the second pressure pipe 522, the first piston 541 and the second piston 542 are disposed on the second closed space 532 side. This causes the recovery valve mechanism 50 to open the communication space 533. Therefore, when the pressure in the first pressure pipe 521 is higher than the pressure in the second pressure pipe 522, the communication space 533 is opened and the recovery passageway 4 is opened.

[0092] A state in which the pressure in the first pressure pipe 521 is higher than the pressure in the second pressure pipe 522 is a state in which the pressure in the first portion 501 is higher than the pressure in the second portion 502, and is a normal state. Therefore, backflow of the cathode off-gas to the anode discharge channel 13 does not occur. Therefore, as described above, the communication space 533 may be open and the recovery channel 4 may be open. Thereby, hydrogen in the anode off-gas continues to be recovered via the recovery channel 4 during electrolysis operation.

[0093] The pressure in the first pressure pipe 521 is equivalent to the pressure in the first portion 501 of the anode discharge passage 13. The pressure in the second pressure pipe 522 is equivalent to the pressure in the second portion 502 (inside the combustor 3 in this embodiment).

[0094] 9, when the pressure in the first pressure pipe 521 is lower than the pressure in the second pressure pipe 522, the first piston 541 and the second piston 542 are disposed on the first closed space 531 side. This causes the recovery valve mechanism 50 to close the communication space 533. Therefore, when the pressure in the first pressure pipe 521 is lower than the pressure in the second pressure pipe 522, the communication space 533 is closed and the recovery passageway 4 is closed.

[0095] A state in which the pressure of the first pressure pipe 521 is lower than the pressure of the second pressure pipe 522 is a state in which the pressure of the first portion 501 is lower than the pressure of the second portion 502. This state occurs due to over-recovery of anode off-gas via the recovery passageway 4. In this state, there is a concern that the cathode off-gas may backflow into the anode discharge passage 13. Therefore, as described above, the communication space 533 is closed and the recovery passageway 4 is closed, thereby increasing the pressure in the first portion 501 of the first pressure pipe 521. This prevents the cathode off-gas from backflowing into the anode discharge passage 13.

[0096] The above description is mainly about the electrolysis operation of the fuel cell system 1, and is based on the premise that the recovery control valve 41 is open. The same is true in the following descriptions and in the seventh and subsequent embodiments, unless otherwise specified. The rest is the same as in the first embodiment.

[0097] In this embodiment, as described above, the recovery valve mechanism 50 is configured to open and close in response to the pressure in the anode discharge channel 13. This makes it possible to adjust the pressure in the anode discharge channel 13 by opening and closing the recovery flow path 4. In other words, when the possibility of backflow of the cathode off-gas into the anode discharge channel 13 increases, the pressure in the first portion 501 of the anode discharge channel 13 can be increased. As a result, backflow of the cathode off-gas into the anode discharge channel 13 can be effectively prevented. On the other hand, when there is no risk of backflow, hydrogen in the anode off-gas can be efficiently recovered.

[0098] Moreover, the recovery valve mechanism 50 opens and closes based on the pressure difference between the pressure at the first portion 501 and the pressure at the second portion 502. This makes it possible to easily and reliably open and close the recovery valve mechanism 50 and effectively prevent backflow of the cathode off-gas.

[0099] In addition, the anode discharge passage 13 has a pressure loss portion 51. This makes it easy to increase the pressure difference between the first portion 501 and the second portion 502. Therefore, the recovery valve mechanism 50 can be reliably opened and closed based on the pressure difference.

[0100] In addition, the backflow prevention mechanism has a first pressure pipe 521 and a second pressure pipe 522. This makes it possible to mechanically open and close the recovery valve mechanism 50 by utilizing the pressure difference between the first portion 501 and the second portion 502. This makes it possible to easily and reliably prevent backflow of the cathode off-gas. In addition, the same effects as those of the first embodiment can be obtained.

[0101] (Embodiment 7) As shown in Figs. 10 and 11, this embodiment is an embodiment in which the structure of the recovery valve mechanism 50 is modified from that of the sixth embodiment. The recovery valve mechanism 50 has a first pressure-receiving surface 551 that receives the pressure of the first pressure pipe 521, and a second pressure-receiving surface 552 that receives the pressure of the second pressure pipe 522. In this embodiment, the first pressure-receiving surface 551 and the second pressure-receiving surface 552 have different pressure-receiving areas.

[0102] In this embodiment, the pressure receiving area of ​​the first pressure receiving surface 551 is smaller than the pressure receiving area of ​​the second pressure receiving surface 552. Therefore, for example, when the pressure in the first pressure pipe 521 and the pressure in the second pressure pipe 522 are equivalent, the first piston 541 and the second piston 542 are disposed on the first closed space 531 side as shown in Fig. 11. As a result, when the pressure in the first pressure pipe 521 and the pressure in the second pressure pipe 522 are equivalent, the communication space 533 is closed and the recovery passageway 4 is closed.

[0103] This is because the force acting on the first piston 541 and the second piston 542 is determined by the product of the pressure acting on each pressure receiving surface and the pressure receiving area. Therefore, for example, when the pressure receiving area of ​​the second pressure receiving surface 552 is twice the pressure receiving area of ​​the first pressure receiving surface 551, the condition for closing the communication space 533 is that the pressure of the second pressure pipe 522 exceeds half the pressure of the first pressure pipe 521. In this case, when the pressure of the second pressure pipe 522 is less than half the pressure of the first pressure pipe 521, the communication space 533 is opened as shown in FIG. The rest is the same as in the sixth embodiment.

[0104] In this embodiment, by changing the pressure receiving area of ​​the first pressure receiving surface 551 and the pressure receiving area of ​​the second pressure receiving surface 552, the conditions for opening and closing the communication space 533 can be changed. For example, as in the above example, by making the pressure-receiving area of ​​the second pressure-receiving surface 552 larger than that of the first pressure-receiving surface 551, it is possible to prevent the recovery passageway 4 from being opened unless the pressure in the first pressure pipe 521 is considerably greater than the pressure in the second pressure pipe 522. This makes it possible to more reliably prevent backflow of the cathode off-gas in the anode discharge passage 13. In addition, the same effects as those of the sixth embodiment are obtained.

[0105] (Embodiment 8) In this embodiment, as shown in FIGS. 12 and 13, an elastic member 56 is used as a part of the recovery valve mechanism 50. As shown in FIG. In this embodiment, the recovery valve mechanism 50 includes an elastic member 56 that is elastically deformed in response to the pressure in the anode discharge passage 13. The recovery valve mechanism 50 is configured to open and close by the elastic deformation of the elastic member 56. The elastic member 56 is disposed between the second piston 542 and the cylinder 53. The first piston 541 and the second piston 542 are biased toward the first closed space 531 by the elastic member 56.

[0106] In this embodiment, for example, when the pressure in the first pressure pipe 521 and the pressure in the second pressure pipe 522 are equal, the first piston 541 and the second piston 542 are positioned toward the first closed space 531 due to the biasing force (i.e., the restoring force) of the elastic member 56, as shown in FIG. 13.

[0107] When the pressure in the first pressure pipe 521 is higher than the pressure in the second pressure pipe 522 by a certain amount or more, as shown in Figure 12, the first piston 541 and the second piston 542 are positioned toward the second closed space 532, and the communicating space 533 is opened. The elastic member 6 may be, for example, a coil spring. The rest is the same as in the sixth embodiment.

[0108] In this embodiment, by adjusting the biasing force of the elastic member 56, the opening and closing conditions of the recovery valve mechanism 50 can be easily adjusted. In addition, the same effects as those of the sixth embodiment are obtained.

[0109] (Embodiment 9) In this embodiment, as shown in FIGS. 14 and 15, a diaphragm is used as a part of the recovery valve mechanism 50. As shown in FIG. That is, in this embodiment, the recovery valve mechanism 50 has a slide valve 58, a housing 59, a first diaphragm 571, and a second diaphragm 572. The housing 59 has a holding portion 591 that slidably holds the slide valve 58, and has a first closed space 531 and a second closed space 532 on both sides of the holding portion 591. The slide valve 58 has a through hole 581 in a direction perpendicular to the sliding direction. Furthermore, the holding portion 591 has an opening 592 formed in a direction perpendicular to the sliding direction. The recovery flow path 4 is connected to the opening 592.

[0110] The first diaphragm 571 and the second diaphragm 572 have their respective outer peripheral edges fixed to the inner surface of the housing 59. Both ends of the slide valve 58 are fixed to the center of the first diaphragm 571 and the center of the second diaphragm 572, respectively. A first closed space 531 is formed between the first diaphragm 571 and the housing 59. A second closed space 532 is formed between the second diaphragm 572 and the housing 59.

[0111] Depending on the relationship between the pressure in the first closed space 531 and the pressure in the second closed space 532, the first diaphragm 571 and the second diaphragm 572 are deformed as shown in FIGS. 14 and 15, and the position of the slide valve 58 changes.

[0112] 14, when the pressure in the first closed space 531 is higher than the pressure in the second closed space 532, the first diaphragm 571 and the second diaphragm 572 are deformed so that the first closed space 531 becomes larger and the second closed space 532 becomes smaller. Accordingly, the slide valve 58 is disposed on the second closed space 532 side. As a result, the through hole 581 of the slide valve 58 overlaps with the opening 592 of the holding portion 591, and the recovery passageway 4 is opened.

[0113] 15, when the pressure in the first closed space 531 is lower than the pressure in the second closed space 532, the first diaphragm 571 and the second diaphragm 572 are deformed so that the first closed space 531 becomes smaller and the second closed space 532 becomes larger. Accordingly, the slide valve 58 is disposed on the first closed space 531 side. As a result, the through hole 581 of the slide valve 58 is misaligned with the opening 592 of the holding portion 591, and the recovery passageway 4 is closed. The rest is the same as in the sixth embodiment.

[0114] In this embodiment, airtightness between the first closed space 531 and the second closed space 532 is easily ensured. In addition, the same effects as those of the sixth embodiment are obtained.

[0115] (Embodiment 10) As shown in FIG. 16, this embodiment is a fuel cell system 1 that is based on the configuration of the sixth embodiment and is further embodied. The components of the fuel cell system 1 are generally similar to those in the third embodiment. However, some of the configuration, such as the routing of the anode discharge passage 13, is different from that shown in the third embodiment.

[0116] In this embodiment, the recovery valve mechanism 50 is provided downstream of the recovery control valve 41 in the recovery flow path 4 . The rest is the same as in the sixth embodiment, and has the same functions and effects as in the sixth embodiment. Moreover, the same functions and effects as in the third embodiment can be obtained with respect to the same configuration as in the third embodiment.

[0117] (Embodiment 11) As shown in FIG. 17, this embodiment is an embodiment in which the position of the second portion 502 to which the second pressure pipe 522 is connected is changed from that of the tenth embodiment. That is, in this embodiment, the second portion 502 is the combustion gas outlet 31 of the combustor 3. And, the anode exhaust passage 13 is not particularly provided with a pressure drop portion 51. The rest is the same as in the tenth embodiment. In this embodiment as well, the same effects as those of the tenth embodiment can be obtained.

[0118] (Embodiment 12) In this embodiment, as shown in FIG. 18, the recovery valve mechanism 50 is opened and closed using signals from pressure gauges 61 and 62. For example, a first pressure gauge 61 is provided in the anode discharge passage 13, and a second pressure gauge 62 is provided in the combustion gas outlet 31. The first pressure gauge 61 and the second pressure gauge 62 are configured to detect the pressures in the first portion 501 and the second portion 502, respectively, and convert them into electrical signals corresponding to the detected pressures. The first pressure gauge 61 and the second pressure gauge 62 are electrically connected to a control device 63. The control device 63 can be configured, for example, by a well-known microcomputer including a CPU, ROM, RAM, etc., and its peripheral circuits.

[0119] The control device 63 is also electrically connected to the recovery valve mechanism 50. The recovery valve mechanism 50 is driven to open and close based on a valve opening and closing signal from the control device 63. With this configuration, the control device 63 transmits a valve opening / closing signal to the recovery valve mechanism 50 in accordance with the pressure difference between the first portion 501 and the second portion 502. This makes it possible to close the recovery valve mechanism 50 when, for example, it is determined that there is a concern about backflow of cathode off-gas in the anode discharge channel 13 based on the pressure difference. The rest is the same as in the sixth embodiment.

[0120] In this embodiment, the recovery valve mechanism 50 is driven via an electric signal. Therefore, the backflow of the cathode off-gas in the anode discharge passage 13 can be prevented with a relatively simple configuration.

[0121] (Embodiment 13) In this embodiment, as shown in FIGS. 19 to 21, the recovery valve mechanism 50 is configured to open and close based on the pressure at a predetermined location in the anode discharge channel 13. That is, in embodiments 6 to 12, a configuration was described in which the recovery valve mechanism 50 is opened and closed based on the pressure difference between the first portion 501 and the second portion 502, but in this embodiment, the recovery valve mechanism 50 is opened and closed based on the pressure at the first portion 501.

[0122] 19, the configuration of this embodiment is a configuration in which the second pressure pipe 522 is removed from the configuration of embodiment 11 (see FIG. 17). In this embodiment, a first pressure pipe 521 is connected to the recovery valve mechanism 50.

[0123] As a result, the recovery valve mechanism 50 is opened and closed based on the pressure in the first pressure pipe 521 (i.e., the pressure in the first portion 501). In other words, when the pressure in the first pressure pipe 521 falls below a predetermined threshold, the recovery valve mechanism 50 is configured to close.

[0124] 20 and 21 are possible configurations for realizing the function of this recovery valve mechanism 50. This recovery valve mechanism 50 has a configuration in which a first piston 541 and a second piston 542 are biased toward the first closed space 531 by an elastic member 56. This recovery valve mechanism 50 can have substantially the same structure as the recovery valve mechanism shown in the above-mentioned embodiment 8 (see FIGS. 12 and 13), except that the second pressure pipe 522 is not connected.

[0125] By adjusting the restoring force (for example, the spring constant) of the elastic member 56 in the recovery valve mechanism 50, the threshold value can be adjusted appropriately. The rest is the same as in the sixth embodiment. In this embodiment, the configuration can be relatively simplified. In addition, the same effects as those of the sixth embodiment are obtained.

[0126] In the sixth to thirteenth embodiments described above, the recovery valve mechanism 50 may be configured to be capable of adjusting the flow rate. That is, for example, the recovery valve mechanism 50 may be configured to be capable of varying the flow path cross-sectional area of ​​the communication space 533 in accordance with the pressure difference between the first portion and the second portion or the pressure in the first portion 501. This makes it possible to change the flow rate of the anode off-gas flowing through the recovery flow path 4 in accordance with the pressure difference or the like.

[0127] In the above embodiment, a configuration has been shown in which either the anode preheater 43 or the cathode preheater 42 is provided in the anode exhaust path 13 or the cathode exhaust path 14. However, the present disclosure is not limited to this, and can also be applied to, for example, a configuration in which both the anode preheater 43 and the cathode preheater 42 are provided in the anode exhaust path 13 or the cathode exhaust path 14.

[0128] The present invention is not limited to the above-described embodiments, and can be applied to various embodiments without departing from the gist of the present invention. [Explanation of symbols]

[0129] 1. Fuel cell system 13 Anode discharge channel 14 Cathode exhaust channel 2 fuel cell 21 Anode flow path 22 Cathode flow path 3. Combustor 4 Recovery channel 5 Discharge valve mechanism (backflow prevention mechanism)

Claims

1. A fuel cell system (1) capable of switching between power generation and electrolysis, A fuel cell (2) having an anode flow path (21) and a cathode flow path (22); a combustor (3) that mixes and combusts the anode off-gas discharged from the anode flow channel and the cathode off-gas discharged from the cathode flow channel; an anode exhaust passage (13) connecting the anode flow passage and the combustor; a cathode exhaust passage (14) connecting the cathode flow passage and the combustor; a recovery passage (4) for recovering the anode off-gas containing hydrogen; a backflow prevention mechanism (5, 50) for preventing the cathode off-gas from flowing back through the anode exhaust passage; having the backflow prevention mechanism is provided in the anode exhaust passage and is configured by a discharge passage valve mechanism (5) that prevents the cathode off-gas from flowing back through the anode exhaust passage, the anode exhaust path is provided with at least one of an anode preheater (43) that preheats an anode supply gas to be supplied to the anode flow path and a cathode preheater (42) that preheats a cathode supply gas to be supplied to the cathode flow path, and the exhaust path valve mechanism is provided downstream of the anode preheater or the cathode preheater.

2. 2. The fuel cell system according to claim 1, wherein the anode discharge path has a common flow path shared with the recovery flow path, at least one of the anode preheater and the cathode preheater is provided in the common flow path, and the discharge path valve mechanism is disposed downstream of a branch point of the anode discharge path with the recovery flow path.

3. 3. The fuel cell system according to claim 1, wherein the exhaust passage valve mechanism is a check valve.

4. A fuel cell system (1) capable of switching between power generation and electrolysis, A fuel cell (2) having an anode flow path (21) and a cathode flow path (22); a combustor (3) that mixes and combusts the anode off-gas discharged from the anode flow channel and the cathode off-gas discharged from the cathode flow channel; an anode exhaust passage (13) connecting the anode flow passage and the combustor; a cathode exhaust passage (14) connecting the cathode flow passage and the combustor; a recovery passage (4) for recovering the anode off-gas containing hydrogen; a backflow prevention mechanism (5, 50) for preventing the cathode off-gas from flowing back through the anode exhaust passage; having the backflow prevention mechanism is provided in the anode exhaust passage and is configured by a discharge passage valve mechanism (5) that prevents the cathode off-gas from flowing back through the anode exhaust passage, The fuel cell system, wherein the exhaust passage valve mechanism is configured with a check valve.

5. A fuel cell system (1) capable of switching between power generation and electrolysis, A fuel cell (2) having an anode flow path (21) and a cathode flow path (22); a combustor (3) that mixes and combusts the anode off-gas discharged from the anode flow channel and the cathode off-gas discharged from the cathode flow channel; an anode exhaust passage (13) connecting the anode flow passage and the combustor; a cathode exhaust passage (14) connecting the cathode flow passage and the combustor; a recovery passage (4) for recovering the anode off-gas containing hydrogen; a backflow prevention mechanism (5, 50) for preventing the cathode off-gas from flowing back through the anode exhaust passage; having The backflow prevention mechanism has a recovery valve mechanism (50) provided in the recovery flow path, the recovery valve mechanism being configured to open and close in response to the pressure in the anode discharge path.

6. 6. The fuel cell system of claim 5, wherein the backflow prevention mechanism further has a pressure pipe (521, 522) connecting the recovery valve mechanism and the anode discharge path, and is configured to drive the recovery valve mechanism by the pressure of the pressure pipe associated with the pressure of the anode discharge path.

7. 7. The fuel cell system according to claim 5, wherein the recovery valve mechanism includes an elastic member (56) that is elastically deformed in response to pressure in the anode discharge passage, and is configured to open and close by elastic deformation of the elastic member.

8. 6. The fuel cell system according to claim 5, wherein the recovery valve mechanism is configured to open and close based on a pressure difference between a predetermined first portion (501) in the anode exhaust passage and a pressure in a second portion (502) downstream of the first portion, and the second portion is a portion in the anode exhaust passage downstream of the first portion, within the combustor, or a combustion gas outlet that discharges combustion gas from the combustor.

9. 9. The fuel cell system according to claim 8, wherein the anode exhaust passage has a pressure loss portion (51) between the first portion and the second portion.

10. 10. The fuel cell system of claim 8 or 9, wherein the backflow prevention mechanism further has a first pressure pipe (521) connecting the recovery valve mechanism and the first portion, and a second pressure pipe (522) connecting the recovery valve mechanism and the second portion, and is configured to drive the recovery valve mechanism by the pressure difference between the pressure in the first pressure pipe and the pressure in the second pressure pipe.

11. 11. The fuel cell system of claim 10, wherein the recovery valve mechanism has a first pressure-receiving surface (551) that receives the pressure of the first pressure piping and a second pressure-receiving surface (552) that receives the pressure of the second pressure piping, and the first pressure-receiving surface and the second pressure-receiving surface have different pressure-receiving areas.

12. 12. The fuel cell system according to claim 5, wherein the recovery valve mechanism is configured to be capable of adjusting a flow rate.

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