Method for aging fuel cell stack

Abstract

To reduce the energy required to humidify oxidizer gas in a method for aging a fuel cell stack.SOLUTION: A fuel cell stack includes a fuel cell equipped with an oxidant gas inlet manifold, a cooling water inlet manifold, and a cooling water outlet manifold, and the aging method includes an aging step in which oxidant gas and water are mixed and introduced through the oxidant gas inlet manifold, and in the aging step, the oxidant gas inlet manifold is set to be closer to the cooling water outlet manifold than the cooling water inlet manifold.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for aging a fuel cell stack. [Background technology]

[0002] After assembly, fuel cell stacks can have insufficient power generation performance due to the adhesion of impurities to the catalyst layer or an insufficient moisture content in the electrolyte layer. To improve power generation performance, a fuel cell stack aging method is known in which the humidity of the gas supplied to the fuel cell stack is increased to promote cleaning of the catalyst layer and moisture content of the electrolyte layer (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-208299 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional aging methods require the use of a humidifying device such as a bubbler to generate steam in order to humidify the gas supplied to the fuel cell stack, which poses the problem of increasing the energy required to humidify the gas. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms.

[0006] According to one aspect of the present disclosure, there is provided an aging method for a fuel cell stack, the fuel cell stack having fuel cells each including an oxidant gas inlet manifold, a cooling water inlet manifold, and a cooling water outlet manifold, the aging method including an aging step of mixing oxidant gas and water and introducing the mixture through the oxidant gas inlet manifold, the oxidant gas inlet manifold being positioned closer to the cooling water outlet manifold than the cooling water inlet manifold. According to this form of aging method for a fuel cell stack, in the aging process, the oxidant gas inlet manifold is set to be closer to the cooling water outlet manifold than the cooling water inlet manifold. Therefore, the cooling water that is heated inside the fuel cell stack and flows at a high temperature can be used to promote evaporation of the water flowing through the oxidant gas inlet manifold, thereby reducing the energy required to humidify the oxidant gas. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is an explanatory diagram showing a schematic configuration of a fuel cell system to which an aging method of an embodiment of the present invention is applied; [Figure 2] 1 is an explanatory diagram showing a schematic configuration of a fuel cell system to which an aging method of an embodiment of the present invention is applied; [Figure 3] 1 is a plan view showing a schematic configuration of a fuel cell according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] A. Implementation: 1 and 2 are explanatory diagrams showing the schematic configuration of a fuel cell system 100 to which the aging method of this embodiment is applied. The fuel cell system 100 is mounted, for example, on a fuel cell vehicle. As shown in FIG. 1, the fuel cell system 100 includes a fuel cell stack 10, a fuel gas supply pipe 21, a fuel off-gas discharge pipe 22, an oxidant gas supply pipe 31, an oxidant off-gas discharge pipe 32, a first coolant supply / discharge pipe 41, and a second coolant supply / discharge pipe 42. The fuel cell system 100 supplies electric power generated by the fuel cell stack 10 to a load mounted on the vehicle. The load includes, for example, a drive motor that is a driving power source for the vehicle, electrical components and accessories of the vehicle, and a connector used for external power supply.

[0009] The fuel cell stack 10 is configured by stacking a plurality of fuel cell units 11 in the thickness direction, which generate electricity through an electrochemical reaction between fuel and an oxidant. In this embodiment, the fuel is hydrogen, the oxidant is oxygen in the air, and hydrogen gas is used as the fuel gas and air as the oxidant gas. In FIG. 1, arrows indicate the flow directions of hydrogen gas, air, and coolant in the aging process described below. In FIG. 2, arrows indicate the flow directions of hydrogen gas, air, and coolant in the power generation process described below.

[0010] Each fuel cell 11 is a power-generating element capable of generating electricity by itself, and includes a membrane electrode assembly (MEA) in which an anode and a cathode are bonded to either side of an electrolyte layer, and two separators sandwiching the membrane electrode assembly. The electrolyte layer is made of a solid polymer thin film that exhibits good proton conductivity when wet with water. A catalyst that promotes the electrochemical reaction of fuel gas and oxidant gas is disposed on the electrodes. The catalyst may be made of platinum (Pt), for example, and gas diffusion layers with gas permeability and electron conductivity may be disposed on the anode and cathode surfaces of the membrane electrode assembly.

[0011] In this embodiment, after the fuel cell stack 10 is assembled, the fuel cell stack 10 is aged for a predetermined period of time to stabilize the power generation performance of the fuel cell stack 10. In the following description, the process of performing the aging process is referred to as the "aging process," and the process of generating power to be supplied to a load is also referred to as the "power generation process." In the aging process, an oxidant gas and moisture are mixed in the oxidant gas supply pipe 31 (described below) and flow into the fuel cell stack 10. The moisture is supplied, for example, as flowing water or dispersed in a mist through a pipe (not shown) connected to the oxidant gas supply pipe 31. Supplying moisture into the fuel cell stack 10 can remove impurities adhering to the catalyst layer (not shown) of the fuel cell stack 10 and promote the hydration of the electrolyte layer (not shown).

[0012] The fuel gas supply pipe 21 is provided between a hydrogen gas tank (not shown) and the fuel cell stack 10, and supplies hydrogen gas as fuel gas to the fuel cell stack 10. The fuel off-gas discharge pipe 22 is connected to the fuel cell stack 10, and discharges the fuel off-gas discharged from the fuel cell stack 10 to the outside. The fuel off-gas may contain fuel gas not used in the electrochemical reaction, inert gases such as nitrogen gas, and water produced by the electrochemical reaction. The fuel off-gas may be separated from impurities such as water by a gas-liquid separator (not shown), and then passed through a circulation pipe (not shown) to join the fuel gas supply pipe 21 and be supplied again to the fuel cell stack 10.

[0013] The oxidant gas supply pipe 31 is provided between an air compressor (not shown) and the fuel cell stack 10, and supplies air as an oxidant gas to the fuel cell stack 10. The fuel off-gas discharge pipe 22 is connected to the fuel cell stack 10, and discharges the oxidant off-gas discharged from the fuel cell stack 10 to the outside. The oxidant off-gas may include oxidant gas not used in the electrochemical reaction, inert gases such as nitrogen gas, and water produced by the electrochemical reaction.

[0014] The first coolant supply / discharge pipe 41 and the second coolant supply / discharge pipe 42 supply coolant as a cooling medium to the fuel cell stack 10 and discharge coolant from the fuel cell stack 10. The cooling medium is not limited to water, and an antifreeze such as ethylene glycol may be used. The first coolant supply / discharge pipe 41 and the second coolant supply / discharge pipe 42 are connected to each other via a radiator (not shown) and a coolant pump (not shown), and circulate the cooling medium in the fuel cell stack 10. More specifically, after being supplied to the fuel cell stack 10, the cooling medium absorbs heat inside the fuel cell stack 10, becomes hot, is discharged, is cooled by the radiator, is pumped by the coolant pump, and is supplied again to the fuel cell stack 10. This circulation allows the temperature of the fuel cell stack 10 to be adjusted.

[0015] In this embodiment, in the aging process shown in Fig. 1, the first cooling water supply / discharge pipe 41 functions as a cooling water supply pipe, and the second cooling water supply / discharge pipe 42 functions as a cooling water discharge pipe. Also, in the power generation process shown in Fig. 2, the first cooling water supply / discharge pipe 41 functions as a cooling water discharge pipe that discharges cooling water, and the second cooling water supply / discharge pipe 42 functions as a cooling water supply pipe that supplies cooling water. That is, in this embodiment, the cooling water supply direction is reversed between the aging process and the power generation process. The cooling water supply direction can be switched, for example, by controlling a refrigerant pump (not shown).

[0016] 1 and 2, the fuel gas supply pipe 21, the first cooling water supply / discharge pipe 41, and the oxidant off-gas discharge pipe 32 are provided in this order at one end of the fuel cell stack 10 in the stacking direction. The oxidant gas supply pipe 31, the second cooling water supply / discharge pipe 42, and the fuel off-gas discharge pipe 22 are provided in this order at the other end of the fuel cell stack 10 in the stacking direction.

[0017] Fig. 3 is a plan view showing a schematic configuration of a fuel cell 11 of this embodiment. As shown in Fig. 3, the fuel cell 11 has a fuel gas inlet manifold 12a, a fuel gas outlet manifold 12b, an oxidant gas inlet manifold 13a, an oxidant gas outlet manifold 13b, a first coolant manifold 14a, and a second coolant manifold 14b.

[0018] The fuel gas inlet manifold 12a is connected to the fuel gas supply pipe 21, through which the fuel gas flows, and the fuel gas outlet manifold 12b is connected to the fuel off-gas discharge pipe 22, through which the fuel off-gas flows.

[0019] The oxidant gas inlet manifold 13a is connected to the oxidant gas supply pipe 31, through which the oxidant gas flows, and the oxidant gas outlet manifold 13b is connected to the oxidant off-gas discharge pipe 32, through which the oxidant off-gas flows.

[0020] The first cooling water manifold 14a is connected to the above-mentioned first cooling water supply / discharge pipe 41, through which the cooling water flows. The second cooling water manifold 14b is connected to the above-mentioned second cooling water supply / discharge pipe 42, through which the cooling water flows. That is, in the aging process shown in FIG. 1, the first cooling water manifold 14a functions as a cooling water inlet manifold, and the second cooling water manifold 14b functions as a cooling water outlet manifold. On the other hand, in the power generation process shown in FIG. 2, the first cooling water manifold 14a functions as a cooling water outlet manifold, and the second cooling water manifold 14b functions as a cooling water inlet manifold.

[0021] As shown in FIG. 3 , in the fuel cell 11, the fuel gas inlet manifold 12a, the first cooling water manifold 14a, and the oxidant gas outlet manifold 13b are provided in this order at one end of the fuel cell 11 in the longitudinal direction. In addition, in the fuel cell 11, the oxidant gas inlet manifold 13a, the second cooling water manifold 14b, and the fuel gas outlet manifold 12b are provided in this order at the other end of the fuel cell 11 in the longitudinal direction. By arranging the manifolds in this manner, in the aging process, the oxidant gas inlet manifold 13a can be positioned closer to the second cooling water manifold 14b, which functions as the cooling water outlet manifold, than to the first cooling water manifold 14a, which functions as the cooling water inlet manifold. In this way, in the aging process, the cooling water that is heated to a high temperature inside the fuel cell stack 10 and discharged can be used to promote evaporation of the moisture flowing in from the oxidant gas inlet manifold 13a without the need for a humidifying device such as a bubbler, thereby reducing the energy required to humidify the oxidant gas.

[0022] Furthermore, in the power generation process, the oxidant gas inlet manifold 13a can be positioned closer to the second cooling water manifold 14b, which functions as a cooling water inlet manifold, than to the first cooling water manifold 14a, which functions as a cooling water outlet manifold. This allows the area around the oxidant gas inlet manifold 13a, which is prone to heat generation due to active electrochemical reactions caused by high oxidant gas concentration, to be cooled using cooling water that is low in temperature immediately after being introduced into the fuel cell stack 10, thereby preventing overheating of the fuel cell cells 11.

[0023] In the fuel cell stack 10 of the embodiment described above, in the aging process, the oxidant gas inlet manifold 13a is set to be closer to the second coolant manifold 14b, which functions as a coolant outlet manifold, than to the first coolant manifold 14a, which functions as a coolant inlet manifold. Therefore, in the aging process, the coolant heated inside the fuel cell stack 10 and discharged at a high temperature can be used to promote evaporation of the water flowing in from the oxidant gas inlet manifold 13a, and the energy required to humidify the oxidant gas can be reduced.

[0024] B. Other Embodiments: (B1) In the above embodiment, the cooling water supply direction is reversed between the aging process and the power generation process, but the present disclosure is not limited to this. The cooling water supply direction may be set so that the first cooling water supply / discharge pipe 41 functions as the cooling water supply pipe and the second cooling water supply / discharge pipe 42 functions as the cooling water discharge pipe, and may not be changed between the aging process and the power generation process. This configuration also achieves the same effects as the above embodiment.

[0025] The present disclosure is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit thereof. For example, the technical features of the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0026] 10... fuel cell stack, 11... fuel cell cell, 12a... fuel gas inlet manifold, 12b... fuel gas outlet manifold, 13a... oxidant gas inlet manifold, 13b... oxidant gas outlet manifold, 14a... first cooling water manifold, 14b... second cooling water manifold, 21... fuel gas supply piping, 22... fuel off-gas discharge piping, 31... oxidant gas supply piping, 32... oxidant off-gas discharge piping, 41... first cooling water supply / discharge piping, 42... second cooling water supply / discharge piping, 100... fuel cell system

Claims

[Claim 1] 1. A method for aging a fuel cell stack, comprising: the fuel cell stack has fuel cell units each including an oxidant gas inlet manifold, a cooling water inlet manifold, and a cooling water outlet manifold; The aging method includes: an aging step of mixing an oxidant gas and water and flowing the mixture into the oxidant gas inlet manifold; In the aging step, the oxidant gas inlet manifold is set to be closer to the cooling water outlet manifold than the cooling water inlet manifold. Aging method.

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