Fuel cell system

Abstract

The objective is to provide a fuel cell system that minimizes the ingress of condensation water into the fuel cell stack. [Solution] The fuel cell system 10 comprises a fuel cell stack 15 that generates electrical energy by reacting anode gas and cathode gas, an anode-off gas circulation path 30 that recirculates anode-off gas containing anode gas not used in the fuel cell stack 15, an ejector 32 that mixes anode gas supplied from an anode gas supply source with anode-off gas recirculated through the anode-off gas circulation path 30, and an intercooler 38 that cools cathode gas with a refrigerant before supplying it to the fuel cell stack 15. The anode-off gas circulation path 30 has a heat exchange piping section that contacts the intercooler and conducts heat.

Description

Technical Field

[0001] This invention relates to a fuel cell system.

Background Art

[0002] As a conventional technology of a fuel cell system, for example, a fuel cell system disclosed in Patent Document 1 is known. The fuel cell system disclosed in Patent Document 1 is a fuel cell system mounted on a vehicle, and includes a fuel cell stack, an ejector, a fuel gas storage tank, a circulation flow path, and a mixed gas supply flow path. The fuel gas storage tank supplies fuel gas to the ejector, and the circulation flow path is a flow path that recovers the fuel off-gas discharged from each fuel electrode of the fuel cell stack and returns it to the ejector as circulation gas. The mixed gas supply flow path connects the ejector and the fuel cell stack, and is a flow path that enables the supply of the mixed gas including the fuel gas and the circulation gas from the ejector to each fuel electrode of the fuel cell stack. The ejector and the fuel gas storage tank are disposed behind the fuel cell stack in the vehicle, and at least a part of the fuel gas storage tank is disposed outside the fuel cell stack when the vehicle is viewed from the front.

[0003] According to this fuel cell system, the fuel gas supplied from the fuel gas storage tank can receive the heat from the fuel cell stack, the possibility of condensed water entering the fuel cell stack can be reduced, and the decrease in the power generation performance of the fuel cell stack can be suppressed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the fuel cell system disclosed in Patent Document 1 uses the airflow that has passed through the stack surface and received heat to heat the fuel gas storage tank, warming the fuel gas upstream of the ejector. Therefore, when there is no airflow, such as when the vehicle is stopped, condensation may enter the fuel cell stack.

[0006] This invention has been made in view of the above-mentioned problems, and the object of this invention is to provide a fuel cell system that reduces the intrusion of condensation water into the fuel cell stack as much as possible. [Means for solving the problem]

[0007] To solve the above problems, the present invention provides a fuel cell system comprising: a fuel cell stack that generates electrical energy by reacting anode gas and cathode gas; an anode off-gas circulation path that recirculates anode off-gas including anode gas not used in the fuel cell stack; an ejector that mixes anode gas supplied from an anode gas supply source with anode off-gas recirculated through the anode off-gas circulation path; and an intercooler that cools cathode gas with a refrigerant before supplying it to the fuel cell stack, wherein the anode off-gas circulation path has a heat exchange piping section that contacts and conducts heat with the intercooler.

[0008] In this invention, the anode off-gas circulation path has a heat exchange piping section that contacts the intercooler and conducts heat, so the heat exchange piping section can receive heat from the intercooler. As a result, a decrease in the temperature of the recirculated anode off-gas passing through the heat exchange piping section can be prevented, and the generation of condensation water in the recirculated anode off-gas can be reduced as much as possible.

[0009] Furthermore, in the fuel cell system described above, the heat exchange piping section may be configured to have a difference in height so that the flow of recirculated hydrogen gas moves from bottom to top. In this case, the heat exchange piping section has a difference in elevation so that the flow of recirculated hydrogen gas is from bottom to top. Therefore, the recirculated hydrogen gas flows from bottom to top in the heat exchange piping section. Even if condensation water is generated in the heat exchange piping section, the generated condensation water flows downward due to gravity, preventing it from entering the ejector.

[0010] Furthermore, in the fuel cell system described above, an anode outlet may be provided at the bottom of the fuel cell stack for discharging anode off-gas, including anode gas that was not used in the fuel cell stack, and the anode off-gas circulation path may be connected to the anode outlet. In this case, since an exhaust port for discharging anode off-gas, which includes anode gas that was not used in the fuel cell stack, is provided at the bottom of the fuel cell stack, the heat exchange piping section is likely to have a difference in height.

[0011] Furthermore, in the fuel cell system described above, the ejector may be located above the intercooler, and the heat exchange piping may be located below the ejector. In this case, the ejector is located at the top of the intercooler, and the heat exchange piping is located below the ejector, which further suppresses the entry of condensation water into the ejector.

[0012] Furthermore, the fuel cell system described above may be equipped with a gas-liquid separator that separates the anode off-gas in the off-gas circulation path into anode gas and generated water, and the gas-liquid separator may be located at the bottom of the intercooler. In this case, the heat exchange piping section is more likely to have a difference in height, allowing the anode off-gas to flow from bottom to top. Furthermore, it becomes possible to connect the entire heat exchange piping section to the intercooler in a way that facilitates heat conduction, improving the heat retention of the heat exchange piping section.

[0013] Furthermore, in the fuel cell system described above, the intercooler, the ejector, and the gas-liquid separator may be configured to be integrated into a single unit. In this case, since the intercooler, ejector, and gas-liquid separator are integrated, the ejector and gas-liquid separator can more easily receive heat from the intercooler, and condensation of anode off-gas can be further reduced. [Effects of the Invention]

[0014] According to the present invention, a fuel cell system can be provided that minimizes the intrusion of condensation water into the fuel cell stack. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic diagram of a fuel cell system according to an embodiment of the present invention. [Figure 2] This is a schematic perspective view showing a fuel cell system according to an embodiment of the present invention. [Figure 3] This is a schematic front view showing a fuel cell system according to an embodiment of the present invention. [Modes for carrying out the invention]

[0016] (First Embodiment) The fuel cell system according to the first embodiment will now be described with reference to the drawings. The fuel cell system of this embodiment is a vehicle-mounted fuel cell system. The vehicle on which the fuel cell system of this embodiment is installed is, for example, a forklift.

[0017] As shown in FIG. 1, the fuel cell system 10 includes a fuel cell unit 11, a power conversion unit 12 that converts and outputs the power input from the fuel cell unit 11, a load 13 that receives the power output from the power conversion unit 12, and a controller 14. The fuel cell unit 11 outputs the power obtained by power generation to the power conversion unit 12. The power conversion unit 12 converts the power input from the fuel cell unit 11 and outputs it to the load 13. The power conversion unit 12 includes a DC / DC converter and an inverter. The load 13 is an electric motor for running (not shown), and the electric motor is driven by the power output from the power conversion unit 12. The forklift runs by driving the electric motor. The controller 14 controls each part of the fuel cell system 10.

[0018] The fuel cell unit 11 includes a fuel cell stack 15, a cathode system 16, an anode system 17, a diluter 18, and a cooling mechanism 19. The fuel cell stack 15 has a stack structure in which a large number of polymer type single cells (not shown) are stacked, and generates high-output power (electrical energy) by electrochemically reacting hydrogen and oxygen supplied to each cell. The fuel cell includes an anode electrode to which anode gas is supplied, a cathode electrode to which cathode gas is supplied, and an electrolyte membrane disposed between the anode electrode and the cathode electrode. The fuel cell is sandwiched by separators. The fuel cell stack 15 is, for example, a solid polymer fuel cell. In the present embodiment, as shown in FIG. 2, the stacking direction of each fuel cell of the fuel cell stack 15 is substantially horizontal.

[0019] The cathode system 16 has a cathode flow path 20 through which cathode gas flows. The cathode flow path 20 is provided, for example, in the separator facing the cathode electrode in the fuel cell stack 15. The cathode flow path 20 includes a cathode inlet 21 and a cathode outlet 22. The cathode gas flows into the cathode flow path 20 from the cathode inlet 21 and flows out of the cathode flow path 20 from the cathode outlet 22.

[0020] The anode system 17 has an anode flow path 23 through which anode gas flows. The anode flow path 23 is provided, for example, in a separator facing the anode electrode in the fuel cell stack 15. The anode flow path 23 includes an anode inlet 24 and an anode outlet 25. The anode gas flows into the anode flow path 23 from the anode inlet 24 and flows out of the anode flow path 23 from the anode outlet 25. A cathode inlet 21, a cathode outlet 22, an anode inlet 24, and an anode outlet 25 are formed on one end face of the fuel cell stack 15 in the stacking direction of the fuel cell cells. The anode outlet 25 is formed at the lower part on one end face of the fuel cell stack 15. That is, the anode outlet 25 is provided at the lower part of the fuel cell stack 15.

[0021] The fuel cell stack 15 generates electricity by the reaction between the anode gas flowing through the anode flow path 23 and the cathode gas flowing through the cathode flow path 20. The cathode gas is, for example, air containing oxygen gas. The anode gas is, for example, hydrogen gas. Therefore, the fuel cell stack 15 generates electricity by the reaction between the cathode gas and the anode gas.

[0022] As shown in Figure 1, the anode system 17 includes an anode gas tank 26, an anode gas supply passage 27, an anode gas on / off valve 28, an injector 29, an anode off-gas circulation passage 30, a gas-liquid separator 31, an ejector 32, and an exhaust drain valve 33. The anode gas tank 26 corresponds to the anode gas supply source and stores anode gas. The anode gas supply passage 27 is an anode gas supply passage connecting the anode gas tank 26 and the anode inlet 24. An injector 29 is provided between the anode gas tank 26 and the anode inlet 24 in the anode gas supply passage 27. The injector 29 is a solenoid valve that adjusts the amount of anode gas supplied to the fuel cell stack 15. Anode gas is supplied to the injector 29 from the anode gas tank 26. The anode gas injected from the injector 29 is supplied to the fuel cell stack 15 through the anode gas supply passage 27. The amount of anode gas supplied to the fuel cell stack 15 is controlled by controlling the injector 29.

[0023] An anode gas on / off valve 28 is provided between the anode gas tank 26 and the injector 29. The anode gas on / off valve 28 is a solenoid valve that opens and closes the anode gas supply passage 27, and switches between an open state and a closed state to switch the supply and interruption of anode gas to the injector 29.

[0024] The anode off-gas circulation path 30 connects the anode outlet 25 and the anode gas supply path 27. Anode off-gas flows through the anode off-gas circulation path 30. The anode off-gas contains unreacted anode gas that was not used in the fuel cell stack 15 and generated water. Generated water is water produced by the power generation in the fuel cell stack 15. The anode off-gas circulation path 30 is a passage for returning the unreacted anode gas contained in the anode off-gas to the anode gas supply path 27.

[0025] The gas-liquid separator 31 is installed in the anode-off gas circulation path 30. The gas-liquid separator 31 separates the anode-off gas into anode gas and generated water. The generated water separated from the anode-off gas is stored in the gas-liquid separator 31.

[0026] The ejector 32 is located in the anode gas supply path 27, between the injector 29 and the fuel cell stack 15. The injector 29 and the ejector 32 are positioned in the anode gas supply path 27 such that the injector 29 is located upstream of the ejector 32. The ejector 32 introduces the anode gas supplied from the injector 29 and simultaneously draws in unreacted anode off gas from the anode off gas circulation path 30, thereby mixing the anode off gas with the anode gas from the injector 29. The mixed anode gas is then supplied to the fuel cell stack 15. Therefore, only anode gas supplied from the anode gas tank 26 flows upstream of the ejector 32 in the anode gas supply path 27. The injector 29 is a known injector.

[0027] The exhaust and drain valve 33 is connected to the gas-liquid separator 31. The exhaust and drain valve 33 can be switched between an open state and a closed state. When the exhaust and drain valve 33 is open, the generated water is discharged from the gas-liquid separator 31. The exhaust and drain valve 33 may be switched from the closed state to the open state when the amount of generated water stored in the gas-liquid separator 31 exceeds a threshold. The exhaust and drain valve 33 may also be switched from the closed state to the open state after a predetermined amount of time has elapsed.

[0028] The gas-liquid separator 31 is connected to the diluent 18. When the exhaust drain valve 33 is open, the generated water and anode-off gas stored in the gas-liquid separator 31 are supplied to the diluent 18.

[0029] The cathode system 16 includes a supply channel 34 and a discharge channel 35. The cathode system 16 also includes an intake port 36, an electric compressor 37, an intercooler 38, an on-off valve 39, a pressure regulating valve 40, and an exhaust port 41.

[0030] The supply channel 34 is a channel through which cathode gas flows. An intake port 36 is formed at the upstream end of the supply channel 34. The intake port 36 draws in cathode gas containing oxygen gas for supply to the fuel cell stack 15 from outside the fuel cell stack 15. Cathode gas flows from the intake port 36 into the supply channel 34. An air cleaner (not shown) may be provided at the intake port 36. The air cleaner has the function of removing foreign matter from the cathode gas flowing from the intake port 36 into the supply channel 34. The supply channel 34 is connected to the cathode inlet 21.

[0031] The electric compressor 37 compresses the cathode gas flowing into the supply channel 34 from the intake port 36 and supplies it to the fuel cell stack 15. The electric compressor 37 is driven by an electric motor (not shown), and the electric compressor 37 discharges the compressed cathode gas from the supply channel 34 toward the cathode channel 20. The cathode gas discharged from the electric compressor 37 is supplied to the cathode channel 20 of the fuel cell stack 15 through the supply channels 34 and 20.

[0032] The intercooler 38 is located in the supply channel 34 between the electric compressor 37 and the fuel cell stack 15. The intercooler 38 is provided to cool the cathode gas compressed by the electric compressor 37. The cathode gas cooled by the intercooler 38 is supplied to the fuel cell stack 15. The intercooler 38 is provided with a gas flow passage (not shown) through which the cathode gas flows and a refrigerant flow passage (not shown) for a refrigerant that cools the cathode gas. The intercooler 38 is, for example, a drip cup type intercooler. In this embodiment, as shown in Figure 2, the intercooler 38 is installed at a position facing one end face of the fuel cell stack 15.

[0033] The supply passage 34 has a first supply passage section 42, a second supply passage section 43, and a third supply passage section 44. The first supply passage section 42 connects the intake port 36 to the electric compressor 37. The second supply passage section 43 connects the electric compressor 37 to the intercooler 38. The third supply passage section 44 connects the intercooler 38 to the cathode passage 20. The supply passage 34 may also have passages other than the first supply passage section 42, the second supply passage section 43, and the third supply passage section 44.

[0034] In this embodiment, the on-off valve 39 is provided in the third supply channel section 44 between the cathode inlet 21 and the intercooler 38. The on-off valve 39 is, for example, an electrically operated butterfly valve that seals the supply channel section 34. The on-off valve 39 can be switched between an open state and a closed state. When the on-off valve 39 is in the open state, cathode gas is supplied from the supply channel section 34 to the cathode channel section 20 through the cathode inlet 21. A portion of the oxygen gas contained in the cathode gas supplied from the supply channel section 34 to the fuel cell stack 15 is consumed for power generation by the fuel cell stack 15. The on-off valve 39 may also be provided in the first supply channel section 42 or the second supply channel section 43.

[0035] The discharge channel 35 is a channel through which cathode off gas flows. Cathode off gas is the off-gas of the cathode gas discharged from the fuel cell stack 15, and is a gas containing generated water. An exhaust port 41 is formed at the downstream end of the discharge channel 35, and the upstream end of the discharge channel 35 is connected to 21. The exhaust port 41 is located downstream of the diluent 18 in the discharge channel 35. Anode off gas, whose hydrogen gas concentration has decreased due to dilution by the cathode off gas in the diluent 18, is also discharged from the exhaust port 41.

[0036] The discharge channel 35 in this embodiment has a first discharge channel section 45 and a second discharge channel 46. The first discharge channel section 45 connects the cathode outlet 22 and the diluent 18. The second discharge channel 46 connects the diluent 18 and the exhaust port 41. Therefore, cathode off gas flows from the cathode channel 20 to the discharge channel 35 through the cathode outlet 22, passes through the diluent 18, and is discharged from the exhaust port 41. The diluent 18 dilutes the anode off gas supplied from the gas-liquid separator 31 with the cathode off gas and discharges it. The oxygen concentration of the cathode off gas discharged from the fuel cell stack 15 to the discharge channel 35 is lower than the oxygen concentration of the cathode gas supplied to the fuel cell stack 15.

[0037] In this embodiment, a pressure regulating valve 40 is provided in the discharge passage 35. Specifically, it is provided in the second discharge passage 46. The pressure regulating valve 40 is, for example, an electrically operated butterfly valve. The internal pressure of the fuel cell stack 15 is adjusted by adjusting the opening degree of the pressure regulating valve 40. The smaller the opening degree of the pressure regulating valve 40, the higher the internal pressure of the fuel cell stack 15. When the on / off valve 39 and the pressure regulating valve 40 are closed, the cathode passage 20 is sealed.

[0038] Next, the cooling mechanism 19 will be described. The cooling mechanism 19 comprises a refrigerant flow path 51, a refrigerant pump 52, a radiator 53, and a cooling fan 54. The refrigerant flow path 51 is a flow path for circulating refrigerant to cool the fuel cell stack 15. The downstream end of the refrigerant flow path 51 is connected to the refrigerant inlet 55 of the fuel cell stack 15. The upstream end of the refrigerant flow path 51 is connected to the refrigerant outlet 56 of the fuel cell stack 15. The fuel cell stack 15 has an internal refrigerant flow path (not shown) formed within it. The fuel cell stack 15 is cooled by the flow of refrigerant through the internal refrigerant flow path. The refrigerant can be, for example, water or antifreeze, or air may be used. In this embodiment, as shown in Figure 2, a refrigerant inlet 55 and a refrigerant outlet 56 are formed on one end face in the stacking direction of each cell of the fuel cell stack 15.

[0039] The refrigerant flow path 51 is equipped with a refrigerant pump 52, which pumps the refrigerant through the refrigerant flow path 51 toward the refrigerant inlet 55, circulating the refrigerant in one direction through the refrigerant flow path 51. The refrigerant pump 52 is an electric pump driven by an electric motor (not shown).

[0040] A radiator 53 is provided upstream of the refrigerant pump 52 in the refrigerant flow path 51. The radiator 53 is a heat exchanger that exchanges heat between the refrigerant and air. A cooling fan 54 is provided to generate airflow through the radiator 53. The cooling fan 54 is driven by an electric motor (not shown). The operation of the cooling fan 54 generates airflow through the radiator 53, promoting heat exchange between the refrigerant and air.

[0041] In this embodiment, an intercooler 38 is provided between the refrigerant pump 52 and the radiator 53 in the refrigerant flow path 51. The intercooler 38 cools the cathode gas by heat exchange between the cathode gas flowing through the supply flow path 34 and the refrigerant.

[0042] The controller 14 comprises an arithmetic processing unit (not shown) and a storage unit (not shown). The storage unit has at least one of RAM and ROM. The storage unit stores programs or commands configured to cause the arithmetic processing unit to execute processing. The controller 14 may be composed of hardware circuits such as an ASIC or FPGA. The controller 14 controls each part of the fuel cell system 10. Specifically, the controller 14 controls the power conversion unit 12, the fuel cell stack 15, the anode gas shut-off valve 28, the electric compressor 37, the shut-off valve 39, the pressure regulating valve 40, and the refrigerant pump 52.

[0043] In this embodiment, as shown in Figures 2 and 3, the intercooler 38 is connected to a first cathode gas piping section 60 and a second cathode gas piping section 61, as well as a first refrigerant piping section 62 and a second refrigerant piping section 63. The first cathode gas piping section 60 is a piping section that connects the electric compressor 37 and the intercooler 38. The second cathode gas piping section 61 is a piping section that connects the intercooler 38 and the cathode inlet 21. The first cathode gas piping section 60 and the second cathode gas piping section 61 constitute a part of the supply flow path 34. The first refrigerant piping section 62 is a piping section that connects the refrigerant pump 52 and the intercooler 38. The second refrigerant piping section 63 is a piping section that connects the intercooler 38 and the refrigerant inlet 55. The first refrigerant piping section 62 and the second refrigerant piping section 63 constitute a part of the refrigerant flow path 51.

[0044] In this embodiment, an ejector 32 is provided at the top of the intercooler 38, and a gas-liquid separator 31 is provided at the bottom of the intercooler 38. In other words, the intercooler 38, ejector 32, and gas-liquid separator 31 are integrated. The ejector 32 is connected to a first anode gas piping section 64 and a second anode gas piping section 65. The first anode gas piping section 64 is a piping section that connects the injector 29 and the ejector 32. The second anode gas piping section 65 is a piping section that connects the ejector 32 and the anode inlet 24. The first anode gas piping section 64 and the second anode gas piping section 65 constitute a part of the anode gas supply passage 27.

[0045] The gas-liquid separator 31 is connected to a first circulation piping section 66 and a second circulation piping section 67. The first circulation piping section 66 is the piping section that connects the gas-liquid separator 31 to the anode outlet 25. The second circulation piping section 67 is the piping section that connects the gas-liquid separator 31 to the ejector 32. The first circulation piping section 66 and the second circulation piping section 67 constitute a part of the anode-off gas circulation path 30. Note that in Figure 2, for the sake of explanation, the illustration of the first cathode gas piping section 60, the second cathode gas piping section 61, the first refrigerant piping section 62, the second refrigerant piping section 63, the first anode gas piping section 64, the second anode gas piping section 65, and the first circulation piping section 66 has been partially omitted.

[0046] In this embodiment, the second circulation piping section 67 is installed inside the intercooler 38 to suppress condensation of the anode off gas due to the heat of the intercooler 38. In other words, a part of the anode off gas circulation path 30 is connected to the intercooler 38 so as to contact it and conduct heat. Specifically, the second circulation piping section 67 is installed in a position where it can exchange heat with the refrigerant by contacting the refrigerant flow path of the intercooler 38. The second circulation piping section 67 corresponds to a heat exchange piping section that contacts the intercooler 38 and conducts heat. In this embodiment, an ejector 32 is provided at the top of the intercooler 38 and a gas-liquid separator 31 is provided at the bottom of the intercooler 38, so the end of the second circulation piping section 67 on the ejector 32 side is at a higher position than the end of the second circulation piping section 67 on the gas-liquid separator 31 side. In other words, the second circulation piping section 67 has a height difference so that the anode off gas flow is from bottom to top.

[0047] As shown in Figure 3, the second circulation piping section 67 extends in the vertical direction, but the direction of extension of the second circulation piping section 67 is not limited to the vertical direction. The second circulation piping section 67 can be configured such that a vertical component is generated in the anode off-gas flow, and its direction of extension may be inclined with respect to the vertical direction, or it may be configured to be bent in multiple directions.

[0048] The refrigerant flowing through the intercooler 38 absorbs heat from the compressed air flowing through the intercooler 38. Therefore, the heat from the refrigerant in the intercooler 38 helps to keep the second circulation piping section 67 warm. This warming of the second circulation piping section 67 by the heat from the intercooler 38 suppresses condensation of moisture contained in the anode off gas flowing through the second circulation piping section 67.

[0049] Next, the operation of the fuel cell system 10 according to this embodiment will be described. When the fuel cell system 10 is in operation, anode gas is supplied from the anode gas tank 26 to the fuel cell stack 15 via the injector 29 to the ejector 32. The gas containing anode gas that was not used in the fuel cell stack 15 (anode off gas) circulates through the anode off gas circulation path 30 and is separated into anode off gas and generated water in the gas-liquid separator 31. In the ejector 32, the separated unreacted anode gas is mixed with anode off gas, and the mixed gas is supplied to the fuel cell stack 15. The anode off gas flowing through the anode off gas circulation path 30 and the generated water separated from the anode off gas are stored in the gas-liquid separator 31.

[0050] Meanwhile, the cathode gas taken in from the intake port 36 is compressed by the drive of the electric compressor 37, and the compressed cathode gas is cooled by the intercooler 38 before being pumped to the fuel cell stack 15. The pressure regulating valve 40 is controlled by the controller 14 to adjust the pressure of the cathode gas supplied to the fuel cell stack 15. The fuel cell stack 15 generates electricity through the electrochemical reaction of anode gas and cathode gas, and the electricity obtained from the generation is output to the power conversion unit 12. In the power conversion unit 12, the electricity input from the fuel cell unit 11 is converted and output to the load 13. The controller 14 adjusts the output (amount of electricity generated) of the fuel cell stack 15 by adjusting the opening degree of the anode gas on / off valve 28 based on the cell voltage of the fuel cell stack 15 and the pressure of the hydrogen gas, thereby adjusting the hydrogen gas supply flow rate.

[0051] The oxygen concentration of the cathode-off gas discharged from the fuel cell stack 15 to the discharge channel 35 is lower than the oxygen concentration of the cathode gas supplied to the fuel cell stack 15. In the diluent 18, the cathode-off gas dilutes the anode-off gas contained in the generated water supplied from the gas-liquid separator 31. The dilution of the cathode-off gas reduces the hydrogen gas concentration of the anode-off gas. The cathode-off gas containing the diluted anode gas is discharged from the exhaust port 41.

[0052] When the fuel cell system 10 is in operation, the controller 14 activates the refrigerant pump 52 and the cooling fan 54. As a result, the refrigerant circulates in one direction through the refrigerant flow path 51, and an airflow is generated that passes through the radiator 53. The refrigerant that has cooled the fuel cell stack 15 is cooled by heat exchange with the air as it passes through the radiator 53. The refrigerant cooled in the radiator 53 cools the cathode gas compressed in the intercooler 38 before being supplied to the fuel cell stack 15 to cool the fuel cell stack 15. The refrigerant introduced into the intercooler 38 through the first refrigerant piping section 62 flows through the refrigerant flow passage of the intercooler 38, from the top to the bottom of the intercooler 38, and then flows through the second refrigerant piping section 63. Therefore, the lower part of the refrigerant flow passage becomes hotter than the upper part of the refrigerant flow passage.

[0053] Incidentally, the anode off-gas is supplied from the anode outlet 25 to the gas-liquid separator 31 via the first circulation piping section 66, and from the gas-liquid separator 31 to the ejector 32 via the second circulation piping section 67. The second circulation piping section 67 is installed inside the intercooler 38, allowing for heat conduction with the intercooler 38, and is therefore kept warm by the heat of the intercooler 38. In the second circulation piping section 67, the temperature of the anode off-gas on the ejector 32 side is higher than that of the anode off-gas on the gas-liquid separator 31 side due to heat exchange with the intercooler 38. Therefore, a decrease in the temperature of the anode off-gas in the second circulation piping section 67 is prevented, and condensation of the anode off-gas flowing through the second circulation piping section 67 is reduced as much as possible. Furthermore, the second circulation piping section 67 has a difference in height, and is installed so that the anode gas flows from bottom to top. Therefore, even if condensation occurs in the anode gas, the condensed water in the second circulation piping section 67 will flow downward due to gravity. As a result, condensed water will hardly enter the ejector 32.

[0054] The fuel cell system 10 of this embodiment provides the following effects. (1) Since the anode off-gas circulation path 30 has a second circulation piping section 67 which is a heat exchange piping section that comes into contact with the intercooler 38 and conducts heat, the heat exchange piping section can receive heat from the intercooler 38. As a result, a decrease in the temperature of the recirculated anode off-gas passing through the second circulation piping section 67 can be prevented, and the generation of condensation water in the recirculated anode off-gas can be reduced as much as possible.

[0055] (2) The second circulation piping section 67 has a height difference such that the flow of the recirculated anode off gas is from bottom to top, so the recirculated anode off gas flows from bottom to top in the second circulation piping section 67. Even if condensation water is generated in the second circulation piping section 67, the generated condensation water will flow downward in the second circulation piping section 67 due to gravity, and the entry of condensation water into the ejector 32 can be suppressed.

[0056] (3) Since the anode outlet 25 for exhausting anode off gas, including anode gas that was not used in the fuel cell stack 15, is provided at the bottom of the fuel cell stack 15, the second circulation piping section 67 is likely to have a difference in height.

[0057] (4) Since the ejector 32 is located on top of the intercooler 38 and the second circulation piping section 67 is located below the ejector 32, the entry of condensation water into the ejector 32 can be further suppressed.

[0058] (5) The anode off gas circulation path 30 is equipped with a gas-liquid separator 31 that separates the anode off gas into anode gas and generated water, and the gas-liquid separator 31 is located at the bottom of the intercooler 38. This makes it easier for the second circulation piping section 67 to have a height difference, allowing the anode off gas to flow from bottom to top. In addition, it becomes possible to conduct heat to the entire second circulation piping section 67 with the intercooler 38, improving the heat retention of the second circulation piping section 67.

[0059] (6) Since the intercooler 38, ejector 32, and gas-liquid separator 31 are integrated, the ejector 32 and gas-liquid separator 31 can more easily receive heat from the intercooler 38, and condensation of anode off-gas can be further reduced. In addition, the heat retention of the second circulation piping section 67 is further improved as the ejector 32 and gas-liquid separator 31 can more easily receive heat from the intercooler 38. Furthermore, the rigidity of the intercooler 38, ejector 32, and gas-liquid separator 31 can be more easily improved by integrating them.

[0060] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the invention. For example, the following modifications may be made.

[0061] ○ In the above embodiment, the ejector is provided on the top of the intercooler, but this is not the only configuration. The ejector does not necessarily have to be provided on the intercooler; for example, it may be located near the intercooler. ○ In the above embodiment, the heat exchange piping section that contacts the intercooler and conducts heat was assumed to have a height difference so that the anode off gas flow is from bottom to top, but it is not limited to this. As long as the heat exchange piping section can contact the intercooler and conduct heat, there does not need to be a height difference in the heat exchange piping section. Also, even if the heat exchange piping section has a height difference, the anode off gas may flow from top to bottom. ○ In the above embodiment, the first refrigerant piping section is provided at the top of the intercooler and the second refrigerant piping section is provided at the bottom of the intercooler. However, the first refrigerant piping section may be provided at the bottom of the intercooler and the second refrigerant piping section may be provided at the top of the intercooler, so that the refrigerant flows from the bottom to the top of the intercooler. In this case, the top of the intercooler will be hotter than the bottom, so the area near the upper end of the heat exchange piping section will be hotter, making it easier to prevent condensation water from entering the ejector. ○ In the above embodiment, the second circulation piping section, which serves as a heat exchange piping section, is installed inside the intercooler as an example of a part of the anode-off gas circulation path contacting the intercooler and conducting heat, but this is not limited to this. For example, the second circulation piping section, which serves as a heat exchange piping section, may be provided on the outer surface of the intercooler, and the position of the second circulation piping section relative to the intercooler is free as long as it can contact the intercooler and conduct heat. [Explanation of symbols]

[0062] 10 Fuel cell systems 15 Fuel cell stack 16 Cathode System 17 Anode System 18 Diluter 19 Cooling mechanism 21 Cathode Inlet 22 Cathode Outlet 24 Anode Inlet 25 Anode outlets 26 Anode gas tank (anode gas supply source) 27 Anode gas supply channels 29 Injectors 30 Anode Off-Gas Circulation Circuit 31 Gas-liquid separator 32 Ejectors 34 Supply channel 35 Discharge channel 37 Electric compressor 38 Intercooler 51 Refrigerant flow path 55 Refrigerant inlet 56 Refrigerant outlet 60 First cathode gas piping section 61 Second Cathode Gas Piping Section 66 1st circulation piping section 67 2nd circulation piping section (heat exchange piping section)

Claims

1. A fuel cell stack that generates electrical energy by reacting anode gas and cathode gas, An anode off-gas circulation path for recirculating anode off-gas, which includes anode gas that was not used in the aforementioned fuel cell stack, An ejector that mixes anode gas supplied from an anode gas supply source with anode off gas recirculated through the anode off gas circulation path, A fuel cell system having an intercooler that cools the cathode gas with a refrigerant before supplying it to the fuel cell stack, The fuel cell system is characterized in that the anode off-gas circulation path has a heat exchange piping section that contacts the intercooler and conducts heat.

2. The fuel cell system according to claim 1, characterized in that the heat exchange piping section has a height difference such that the flow of anode off gas is from bottom to top.

3. An anode outlet is provided at the bottom of the fuel cell stack for discharging anode off-gas, including anode gas that was not used in the fuel cell stack, from the fuel cell stack. The fuel cell system according to claim 1 or 2, characterized in that the anode off-gas circulation path is connected to the anode outlet.

4. The ejector is provided on top of the intercooler, The fuel cell system according to claim 1 or 2, characterized in that the heat exchange piping section is located below the intercooler.

5. The off-gas circulation path is equipped with a gas-liquid separator that separates the anode off-gas into anode gas and generated water. The fuel cell system according to claim 4, characterized in that the gas-liquid separator is provided below the intercooler.

6. The fuel cell system according to claim 5, characterized in that the intercooler, the ejector, and the gas-liquid separator are integrated into one unit.

Images