Fuel cell system

Abstract

This fuel cell system is equipped with a salt removal mechanism, which reduces the burden on the air filter, and offers advantages in reducing costs and maintenance man-hours, as well as preventing deterioration of the membrane electrode assembly. [Solution] A fuel cell system comprising an air supply line for supplying reaction air to the oxygen electrode of a fuel cell stack and a gas-water separator for separating water from the air discharged from the oxygen electrode is further equipped with a salt removal device in the air supply line for removing salt from outside air and introducing it as reaction air. The salt removal device comprises a processing container for storing the water separated by the gas-water separator and an outside air introduction section for introducing outside air into the water in the processing container in the form of fine bubbles, and is configured so that reaction air is supplied from the upper space of the processing container.

Description

Technical Field

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

Background Art

[0002] A fuel cell is a power generation device that generates electricity through the oxidation-reduction reaction of fuel hydrogen and oxygen in the air, and heat and generated water are generated during power generation. Hydrogen fuel can be supplied from a fuel tank, and it is expected to be used not only for mobile bodies such as electric vehicles and small ships, but also for portable power sources and as a substitute for engine generators in outdoor environments and the like.

[0003] In order to prevent deterioration of the membrane electrode assembly due to impurities contained in the air, a fuel cell is equipped with an air filter on the introduction side of the reaction air. In particular, when use in ships or coastal areas is assumed, in order to prevent deterioration due to salts in the air, measures such as using a large amount of chemical filters such as activated carbon or shortening the filter replacement period are required, resulting in problems such as increased costs and increased maintenance man-hours.

[0004] Patent Document 1 discloses a system that selectively uses two types of air filters and executes a refresh mode with pressurized air when not in use to revive the activity of the filters. However, even in a system that selectively uses two types of air filters, an increase in cost due to duplication is inevitable and it does not provide a fundamental solution.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Disclosure of the Invention

Problems to be Solved by the Invention

[0006] The present invention has been made in view of the above-mentioned points of the prior art, and its purpose is to provide a fuel cell system that reduces the burden on the air filter by providing a salt removal means in addition to the air filter, thereby reducing costs and maintenance man-hours and preventing deterioration of the membrane electrode assembly. [Means for solving the problem]

[0007] In order to solve the above problems, the inventors of this invention conducted diligent research and discovered that salts in the reaction air can be removed by contacting the generated water produced during power generation by a fuel cell with the generated water, which led to the invention.

[0008] In other words, the present invention is Fuel cell stack and An air supply line for supplying reaction air to the oxygen electrode of the fuel cell stack, A gas-water separator for separating water from the air discharged from the oxygen electrode, In a fuel cell system equipped with, The aforementioned air supply line includes a desalination device for removing salt from the outside air and introducing it as reaction air. The salt removal device is A processing container for storing the water separated by the aforementioned gas-water separator, An outside air introduction unit for introducing outside air into the water of the aforementioned processing container by forming it into fine bubbles, Equipped with, The fuel cell system is configured such that reaction air is supplied from the upper space of the processing vessel. [Effects of the Invention]

[0009] As described above, the fuel cell system according to the present invention stores the generated water produced during power generation by the fuel cell stack, and supplies this generated water to the oxygen electrode through an air filter after removing salt by contacting it with reactive air. This configuration reduces the burden on the air filter and is expected to reduce the frequency of replacement. Moreover, since the generated water necessary for salt removal is always produced during power generation, maintenance such as replenishment is basically unnecessary, which is advantageous in reducing costs and preventing deterioration of the membrane electrode assembly. [Brief explanation of the drawing]

[0010] [Figure 1] This is a configuration diagram showing a fuel cell system according to the first embodiment of the present invention. [Figure 2] This is a configuration diagram showing a fuel cell system according to a second embodiment of the present invention. [Figure 3] This is a schematic longitudinal cross-sectional view showing a salt removal device according to an embodiment of the present invention. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described in detail below with reference to the drawings. Figure 1 shows a fuel cell system 100 according to a first embodiment of the present invention. In Figure 1, the fuel cell system 100 includes hydrogen-related equipment such as a hydrogen supply line 21 and a flow control valve 22 for supplying hydrogen fuel from a hydrogen fuel tank 20 to the hydrogen electrode (anode) of the fuel cell stack 30, and a hydrogen circulation line 23 and a hydrogen circulation pump 24 for circulating unreacted hydrogen gas to the hydrogen electrode.

[0012] Furthermore, the fuel cell system 100 is equipped with oxygen-related equipment such as an air supply line 17 that supplies reaction air to the oxygen electrode (cathode) of the fuel cell stack 30, an air filter 18, and a blower 12. The air supply line 17 is also equipped with a salt removal device 110 for removing salt from the outside air. The salt removal device 110 will be described later.

[0013] The fuel cell stack 30 is composed by stacking a large number of unit cells, each unit cell having a membrane electrode assembly (MEA) with electrode layers (anode, cathode) joined to each side of a solid polymer electrolyte membrane that selectively permeates hydrogen ions, and on each side of the MEA, a hydrogen-side separator and an air-side separator are laminated via gas diffusion layers (GDL).

[0014] The hydrogen-side separator and the air-side separator also serve as current collecting electrodes / power feeding electrodes, and are composed of metal materials, carbon materials, etc. with good conductivity and heat conductivity. The gas diffusion layer (GDL) has the function of diffusing hydrogen and oxygen in the plane direction and evenly distributing them to the electrode layers of the membrane electrode assembly, and also has the function of collecting electrons generated by the catalytic reaction at the hydrogen electrode (anode) and discharging the generated water at the air electrode (cathode).

[0015] That is, hydrogen (H2) supplied through the grooves of the hydrogen-side separator is diffused by the gas diffusion layer to the hydrogen electrode (anode) of the membrane electrode assembly, and is decomposed into hydrogen ions (H + ) and electrons (e ― ) by the catalytic reaction in the electrode layer. The electrons (e ― ) are collected through the gas diffusion layer, while the hydrogen ions (H + ) that have permeated through the solid polymer electrolyte membrane combine with oxygen (O2) at the air electrode (cathode) to generate water.

[0016] The water generated at the air electrode (cathode) of the fuel cell stack 30 is discharged through the groove of the air-side separator and the outlet line 31 together with the outlet gas (air off-gas) of the reaction air to the gas-liquid separator 32. The air off-gas is exhausted from the gas-liquid separator 32 to the outside, while the generated water separated from the air off-gas at the gas-liquid separator 32 is temporarily stored in the storage container 34.

[0017] The storage container 34 is connected to the treatment container 14 of the salt removal device 110 through the water supply line 35. The generated water stored in the storage container 34 is discharged by opening the water supply valve 36 when the fuel cell system 100 stops, etc., and is supplied to the treatment container 14.

[0018] On the one hand, the unreacted hydrogen gas (hydrogen off-gas) discharged from the hydrogen electrode (anode) of the fuel cell stack 30 is recycled to the hydrogen electrode through the hydrogen circulation line 23 by the hydrogen circulation pump 24. Such recycling can improve the utilization efficiency of hydrogen fuel. However, since nitrogen in the air supplied to the air electrode (cathode) permeates through the solid polymer electrolyte membrane, if the recycling of hydrogen is continued for a long time, the nitrogen concentration in the hydrogen circulation line 23 increases, the hydrogen concentration supplied to the hydrogen electrode (anode) decreases, and the power generation efficiency decreases.

[0019] Therefore, the fuel cell system 100 periodically opens the purge valve 25 to execute a purge operation of discharging the hydrogen off-gas in the hydrogen circulation line 23 to the outside of the system. At this time, the bypass valve 19 is opened simultaneously with the purge valve 25, and the hydrogen off-gas is diluted to a predetermined concentration or less (for example, 4% or less) by the gas-liquid separator 32 using the air supplied to the air supply line 17 and then discharged.

[0020] The fuel cell system 100 having the above basic configuration is provided with a salt removal device 110 for removing the salt in the air at the introduction part of the outside air to the air supply line 17.

[0021] As schematically shown in FIG. 1, the salt removal device 110 includes a treatment container 14 for storing the generated water separated by the gas-liquid separator 32 and temporarily stored in the storage container 34, and an outside air introduction part 11 for introducing the outside air into the water in the treatment container 14 in the form of fine bubbles.

[0022] The outside air introduction part 11 includes an inlet part 10 arranged outside the treatment container 14, an outlet part 13 arranged in the water below the specified water level of the treatment container 14, and a duct part extending between them, and a blower 12 is provided in this duct part. The inlet part 10 is opened downward to prevent the inflow of rainwater, and is provided with a simple filter structure such as a mesh to prevent the intrusion of foreign matters.

[0023] In a typical embodiment, the outside air intake section 11 includes a first duct section extending upward from the inlet section 10, a second duct section extending substantially horizontally from the upper end of the first duct section, and a third duct section extending downward from the end of the second duct section. A blower 12 is provided in the second duct section, and an outlet section 13 is provided at the lower end of the third duct section.

[0024] As shown in Figure 3, the outlet 13 of the outside air intake section 11 has an enlarged section 131 that expands downward relative to the flow path cross-section of the third duct section. At the lower end of the enlarged section 131, it opens downward toward the bottom 143 of the processing container 14 and is composed of a collection of numerous pores subdivided within a substantially horizontal spread. The numerous pores have a significant length in the vertical direction. Alternatively, the third duct section can branch into multiple flat ducts above (upstream of) the enlarged section 131, and multiple rows of pores can be arranged parallel to each other with spacing at the lower ends of the multiple flat enlarged sections (131).

[0025] The processing container 14 comprises a bottom portion 143, an upper portion 142, and a cylindrical or rectangular side wall portion 141 extending between them. A drain valve 15 for draining water from the processing container 14 is provided in the bottom portion 143. In Figure 3, the bottom portion 143 is flat, but it may have a slope toward the drain valve 15. A water supply line 35 from the storage container 34 is connected to the upper part (or upper portion 142) of the side wall portion 141.

[0026] An air supply line 17 is connected to the upper part 142 of the processing container 14 via a gas-liquid separation unit 16. The system is configured such that reaction air is pumped to the air supply line 17 via the gas-liquid separation unit 16 as the air pressure inside the processing container 14 increases due to the blower 12.

[0027] A water level sensor 144 is provided inside the processing container 14 to detect the water level of the water stored in the processing container 14. The illustrated example shows a case where a float-type level sensor is used as the water level sensor 144, which has a float (144) supported so as to be movable in the vertical direction on a stem 145 extending downward from the center of the upper part 142 of the processing container 14, but the water level sensor 144 may be of other types.

[0028] For example, an ultrasonic level sensor can be used that emits ultrasonic pulses from a sensor unit on the upper part 142 of the processing container 14 toward the liquid surface and detects the water level based on the arrival time of the reflected waves, or a radar level sensor can be used that irradiates microwaves from a sensor unit on the upper part 142 of the processing container 14 toward the liquid surface and detects the water level based on the arrival time of the reflected waves.

[0029] Furthermore, in either case, it is preferable to place the water level sensor 144 in the center of the processing container 14, as shown in Figure 3. With this configuration, when the fuel cell system 100 is mounted on a mobile body such as a ship or vehicle, the water level (water volume) in the processing container 14 can be continuously detected with minimal error even if the water surface is tilted.

[0030] When the fuel cell system 100 equipped with the salt removal device 110 described above is started, outside air drawn in from the inlet 10 to the outside air introduction 11 by the blower 12 is blown into the water in the processing container 14 from the outlet 13. At this time, the airflow is subdivided in the outlet 13, which is composed of many pores, and introduced into the water as fine bubbles. Due to sufficient contact between the outside air and water, salt particles in the outside air dissolve into the water in the processing container 14, and the air from which the salt has been separated and removed is introduced from the upper space of the processing container 14 to the air supply line 17 via the gas-water separation unit 16.

[0031] In this configuration, the air from which salt has been removed is supplied to the air electrode (cathode) of the fuel cell stack 30 via the air filter 18. This eliminates the need for the air filter 18 to be a special chemical filter, thus reducing the cost of the air filter.

[0032] Furthermore, since the salt removal device 110 can remove not only salt but also other fine particles, the frequency of replacing the air filter 18 can be reduced, and combined with the simple filter function of the inlet section 10, the air filter 18 can even be omitted. In addition, it can be expected that the service life of the fuel cell in the coastal environment will be the same as in a normal environment.

[0033] As power generation by the fuel cell system 100 continues, the salinity of the water in the treatment container 14 increases. Therefore, it is necessary to periodically open the drain valve 15 to discharge the treated water, then close the drain valve 15 and open the water supply valve 36 to replenish the water in the treatment container 14 with generated water until the water level reaches the specified level. The timing of this treated water replacement is managed by a control unit (not shown) based on the cumulative operating time of the fuel cell system 100.

[0034] During power generation by the fuel cell system 100, the water level in the treatment container 14 must be maintained above a specified level, and the water supply valve 36 must be kept closed to prevent reaction air from flowing into the water supply line 35. Therefore, the operation to replace the treated water in the treatment container 14 is basically carried out when power generation is stopped.

[0035] Therefore, for example, if a fuel cell system 100 is installed as a power source for a motor that generates thrust in a moving object such as a ship or vehicle, and it is time to replace the treated water while the system is generating power, the power source for the motor is temporarily switched to a battery, power generation is stopped, and the treated water replacement operation is carried out.

[0036] Alternatively, if it is predicted that the treated water will need to be replaced during the next operation when the fuel cell system 100 has finished running, for example, if the remaining time until the next replacement is below a predetermined threshold, the system may be configured to perform the treated water replacement operation at the end of operation.

[0037] Figure 2 shows a fuel cell system 200 according to a second embodiment of the present invention. The basic configuration of this fuel cell system 200, including the salt removal device 110, is the same as that of the fuel cell system 100 of the first embodiment. Similar components are denoted by the same reference numerals, and their descriptions are omitted. The changes will be described below.

[0038] In the fuel cell system 200, a hydrogen dilution unit 27 for diluting the hydrogen off-gas is provided separately from the gas-water separator 33 of the air off-gas outlet line 31. During purging, the bypass valve 19 is opened simultaneously with the purge valve 25, allowing air to be supplied from the air supply line 17 to the hydrogen dilution unit 27, diluting the hydrogen off-gas to a predetermined concentration or lower before it is discharged into the outside air.

[0039] The generated water discharged from the outlet line 31 of the air electrode (cathode) along with the air off-gas is separated from the air off-gas by the gas-water separator 33 and stored in the storage container 34. Meanwhile, the air off-gas from which the generated water has been separated is exhausted to the outside via the hydrogen dilution unit 27. In this configuration, the drainage of treated water from the treatment container 14 and the supply of water from the storage container 34 to the treatment container 14 can be performed in parallel with the purging operation of the hydrogen off-gas. Furthermore, the gas-water separator 33 and the storage container 34 can be integrated.

[0040] Although several embodiments of the present invention have been described above, it should be noted that the present invention is not limited thereto, and various further modifications and changes are possible within the scope of the present invention based on the technical idea of ​​the present invention. [Explanation of symbols]

[0041] 10 Entrance 11. Outside air intake 12 Blower 13 Exit section 14 Processing container 15 Drain valve 16 Air-water separation section 17 Air supply line 18 Air filter 19 Bypass valve 20 Hydrogen fuel tanks 23 Hydrogen circulation line 30 Fuel Cell Modules 31 Exit Line 32,33 Steam water separator 34 Storage containers 35 Water supply line 36 Water supply valve 100,200 fuel cell systems 110 Salt removal device 144 Water level sensor

Claims

1. Fuel cell stack and An air supply line for supplying reaction air to the oxygen electrode of the fuel cell stack, A gas-water separator for separating water from the air discharged from the oxygen electrode, In a fuel cell system equipped with, The air supply line includes a desalination device for removing salt from the outside air and introducing it as reaction air. The salt removal device is A processing container for storing the water separated by the aforementioned gas-water separator, An outside air introduction unit for introducing outside air into the water of the aforementioned processing container by forming it into fine bubbles, A fuel cell system comprising a mechanism configured such that reaction air is supplied from the upper space of the processing vessel.

2. The salt removal device is A storage container for temporarily storing the water separated by the aforementioned gas-water separator, A water supply valve is provided in the water supply line from the storage container to the processing container, A drain valve provided in the drain line of the aforementioned processing container, The fuel cell system according to claim 1, further comprising:

3. The fuel cell system according to claim 2, wherein the outside air intake section includes an inlet located outside the processing container, an outlet located in the water of the processing container, and a duct portion extending between the inlet and the outlet, the outlet opening downward within a substantially horizontal range.

4. The fuel cell system according to claim 3, wherein the outlet portion is composed of a structure of numerous subdivided pores.

5. The fuel cell system according to claim 3, wherein a blower is provided in the duct portion of the outside air intake section for blowing outside air drawn in from the inlet section into the processing container from the outlet section.

6. The fuel cell system according to any one of claims 3 to 5, wherein the salt removal device further comprises a water level sensor for monitoring the water level in the processing container, and the opening and closing of the water supply valve and the drain valve are controlled based on the value detected by the water level sensor, thereby maintaining the water level in the processing container within a predetermined range, and the outlet of the outside air intake unit is maintained within a predetermined water depth range in the processing container.

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