JP2000048842A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To disperse with supply of energy exclusive to a water supply means, and to improve energy efficiency of the whole system by supplying water to a fuel cell stack by driving a water pressurizing means by using pressure of fuel gas. SOLUTION: This hydrogen gas inlet part 110 and the water introducing part 120 are partitioned by a partition wall 130, a bearing 131 is provided in this partition wall 130, a shaft 133 is rotatably fitted there, a first blade 135 is installed on the hydrogen gas inlet part 110 side, and a second blade 136 is installed on the water inlet part 120 side. In this structure, the second blade 136 is rotated through the first blade 135 and the shaft 133 by flowing hydrogen of a hydrogen supply passage 20. Water of the water supply part 61 is pressurized by this rotation to be blown out through a nozzle 55. When intermittently flowing hydrogen gas, a pump device 100 is also driven intermittently. At hydrogen gas flow stopping time, a fuel cell stack 2 becomes an abnormally high temperature, and when requiring to supply water, the water is supplied by the driving of an auxiliary pump.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell system.

[0002]

2. Description of the Related Art A PEM fuel cell body has a structure in which a polymer solid electrolyte membrane is sandwiched between a fuel electrode and an air electrode. Each of the fuel electrode and the air electrode includes a catalyst layer containing a catalyst substance, and an electrode device that supports the catalyst layer, supplies a reaction gas, and has a function as a current collector. A separator (connector plate) is further provided outside the fuel electrode and the air electrode, in which a reaction gas is uniformly supplied from the outside to the inside of the electrode and a gas flow groove for discharging excess gas to the outside is provided. The separator prevents current permeation and performs current collection for taking out the generated current to the outside.

A unit cell is composed of the fuel cell body and the separator. In an actual fuel cell system, a large number of such cells are stacked in series to form a stack. In the fuel cell main body, generally, heat having a calorific value substantially corresponding to generated power is generated. Therefore, in order to prevent the fuel cell body from excessively heating up, a cooling plate is built in the stack. A cooling medium such as air or water flows through the cooling plate to cool the stack, thereby maintaining the fuel cell body at a desired temperature.

[0004] The electromotive force of the fuel cell having such a configuration is such that electrons are generated as the electrochemical reaction proceeds as a result of fuel gas being supplied to the fuel electrode side (anode) and oxidizing gas being supplied to the air electrode side. Then, the electrons are generated by extracting the electrons to an external circuit. That is, the hydrogen ions obtained at the fuel electrode (anode) move in the electrolyte membrane containing water in the form of protons (H ⁺ ) to the air electrode (cathode) side, and are obtained at the fuel electrode (anode). The extracted electrons move to the cathode (cathode) side through an external load and react with oxygen in the oxidizing gas (including air) to produce water. Because you can.

[0005] In the above, since protons take a hydrated state when moving through the electrolyte membrane from the fuel electrode toward the air electrode, if the electrolyte membrane is dried, the ionic conductivity decreases, and energy conversion occurs. Efficiency is reduced. Therefore, it is necessary to supply moisture to the solid electrolyte membrane in order to maintain good ion conduction. For this purpose, the fuel gas and the oxidizing gas are humidified to supply moisture. In addition, on the anode electrode side, it is necessary to maintain a more humidified state of hydrogen gas in order to properly continue the electrode reaction, and there have been various proposals on humidification methods of fuel gas.

On the other hand, a method of humidifying the process air has been proposed. However, in order to humidify the air electrode heated by the reaction heat (usually at about 80 ° C.), the process air at a normal temperature is required. Must be preheated in a humidifier. This is to make the amount of saturated water vapor coincide with the environment around the air electrode. Therefore, the humidifier has a complicated configuration that requires a water supply function and a process air heating function. In the fuel cell device disclosed in Japanese Patent Application Laid-Open No. 7-14599, water required for humidification is sprayed into process air by providing an injection nozzle in an air introduction pipe. When the injection nozzle is located on the upstream side of the compressor, the sprayed water is evaporated by heat accompanying the compression of the process air, and humidifies the air electrode in a state of steam. In this device, an air humidifier is further added as needed. In any case, in the conventional technique, water is supplied to the electrolyte membrane by mixing water vapor into the air.

Further, in the fuel cell apparatus disclosed in Japanese Patent Application Laid-Open No. 9-266004, the gas discharged from the fuel electrode (the unreacted hydrogen gas Is included in the air electrode side, and the hydrogen gas therein is burned at the air electrode. Since reaction water (recovered water) is generated in the combustion, sufficient water can be supplied to the electrolyte membrane in such a fuel cell device without particularly adding a humidifier.

[0008] Further studies have revealed the following: When a fuel cell is constructed with an electrolyte membrane having a thickness equal to or less than a predetermined value, water generated by the reaction of protons with oxygen in the air at the air electrode reversely permeates the electrolyte membrane from the air electrode to the hydrogen electrode. I do. Since the electrolyte membrane can be maintained in a suitable wet state by the reversely osmotic water, it is not necessary to humidify hydrogen (fuel gas) on the hydrogen electrode (anode electrode) side. However, it has been found that the water on the air electrode side of the electrolyte membrane evaporates due to the introduced air (oxidizing gas) flow on the air electrode (cathode electrode) side, so that the water on the air electrode side of the electrolyte membrane becomes insufficient. .

Therefore, the earlier application proposed a water direct injection type fuel cell system in which water is supplied in a liquid state to an air electrode of a fuel cell body. According to the fuel cell system configured as described above, the water supplied to the surface of the air electrode preferentially removes latent heat from the air, so that evaporation of water from the electrolyte membrane on the air electrode side is prevented. Therefore, the electrolyte membrane always maintains a uniform wet state without drying on the air electrode side. Therefore, the performance of the fuel cell system and / or
Or, the durability is improved.

Further, when water is supplied to the air electrode in a liquid state, the water supplied to the surface of the air electrode also removes heat from the air electrode itself and cools it, thereby reducing the temperature of the fuel cell body. Can control. That is, the fuel cell main body can be cooled without adding a cooling plate to the fuel cell stack.

[0011]

There is a need to further improve the efficiency of such a water injection type fuel cell system. In order to increase the efficiency of the fuel cell system, not only increase the efficiency of the power generation reaction in the fuel cell stack, but also simplify the configuration of the fuel cell system itself,
It is also achieved by reducing the energy consumed to drive the system itself. From such a viewpoint, the present inventors have studied to review the overall configuration of the fuel cell system. In the water direct injection type fuel cell system, the amount of water supplied to the fuel cell stack from the water supply system is larger than in the conventional system. Therefore, the energy consumed to drive the pump of the water supply system increases.
This energy is also provided by the fuel cell system itself. Accordingly, it is an object of the present invention to reduce the energy consumed in the water supply system and provide an efficient fuel cell system. Another object of the present invention is to provide a fuel cell system having a novel configuration.

[0012]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above-mentioned object, and has the following structure. A fuel gas stack, a fuel gas supply system for supplying a fuel gas to the fuel cell stack, and a water supply means for supplying water pressurized by water pressurization means to the fuel cell stack; A fuel cell system, wherein the pressure means pressurizes the water using the pressure of the fuel gas.

According to the fuel cell system of the present invention configured as described above, water is supplied to the fuel cell stack using the pressure of the fuel gas. When, for example, hydrogen is used as the fuel gas, the primary pressure of a hydrogen gas tank made of a hydrogen storage alloy or the like greatly exceeds the pressure resistance of the fuel cell stack. According to the present invention, the water pressurizing means of the water supply means is driven by utilizing the excessive pressure of the gas tank to supply water to the fuel cell stack. Therefore, there is no need to supply dedicated energy to the water supply means. Therefore, the energy efficiency of the entire system is improved. Since the water pressurizing means in the water supply system sends water like a pump using the gas pressure of the fuel gas, this means can also be grasped as water sending means.

[0014] It is known that a conventional system supplies moisture (in the form of water vapor) to an air supply system and / or a fuel gas supply system. The present invention seeks to utilize the gas pressure of a fuel gas as an energy source when supplying moisture to a fuel cell stack. From this viewpoint, the present invention relates to a water direct injection type fuel cell system. The present invention is not limited to this, and can be applied to the conventional fuel cell system.

[0015]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration of a fuel cell system 1 according to an embodiment of the present invention. As shown in FIG. 1, the fuel cell system 1 generally includes a fuel cell stack 2, a fuel supply system 10 including a hydrogen storage alloy 11, an air supply system 40, a water supply system 50, and a load system 70.

The fuel cell stack 2 is formed by connecting a plurality of unit units of a fuel cell. This unit is
The fuel cell body has a configuration in which a solid polymer electrolyte is sandwiched between an air electrode and a fuel electrode, and is further sandwiched between carbon black separators. Although the shape of the unit unit is not particularly limited, an air flow path for circulating air is formed vertically between the separator and the air electrode. A hydrogen gas flow path for flowing hydrogen gas is formed between the separator and the fuel electrode.

In the fuel supply system 10, the hydrogen released from the hydrogen storage alloy 11 via the hydrogen supply path 20 is sent to the hydrogen gas flow path of each unit of the fuel stack 2. A hydrogen pressure regulating valve 21 is provided in the hydrogen supply path 20 to regulate the pressure of hydrogen gas released from the hydrogen storage alloy 11. Symbol 23
Is a hydrogen supply solenoid valve 23, which controls opening and closing of the hydrogen supply path 20.

Reference numeral 100 in the figure denotes a pump device (water pressurizing means, water feeding device) for sending water to the air manifold 45 using the gas pressure of hydrogen. The detailed configuration will be described later.

In the fuel supply system 10, hydrogen gas discharged from the fuel cell stack 2 is rendered harmless via a hydrogen exhaust path 30 and discharged to the atmosphere. A check valve 31 and a solenoid valve 33 are provided in the hydrogen exhaust path 30. The check valve 31 prevents air from entering the fuel electrode of the fuel cell stack 2 via the hydrogen exhaust passage 30. The solenoid valve 33 is driven intermittently to positively discharge remaining water (and detoxified gas). The hydrogen exhaust path 30, the check valve 31, and the solenoid valve 33 are collectively called a fuel gas discharge system. Although not shown, a catalytic combustor as a combustion means is disposed in the pipe 30 to catalytically combust the hydrogen discharged from the discharge port and air introduced from the outside, and water (and detoxified gas).
Is discharged through the solenoid valve 33 in the state described above.

The air supply system 40 supplies air from the atmosphere to the air flow path of the fuel cell stack 2 and exhausts the air discharged from the fuel cell stack 2 through a water condenser 51. The air supply path 41 is provided with a fan 43 for sending air from the atmosphere to the air manifold 45. The air flows from the manifold 45 into the air flow path of the fuel cell stack 2 to supply oxygen to the air electrode. The air discharged from the fuel cell stack 2 is condensed and recovered by a water condenser 51 (water recovery device) and released to the atmosphere. The temperature of the air discharged from the fuel cell stack 2 is monitored by an exhaust gas temperature sensor 47.

In this embodiment, a nozzle 55 is provided on the side wall of the air manifold 45, and thereby water is supplied in a liquid state during intake. Most of this water reaches the water condenser 51 while maintaining the liquid state, and is sent to the tank 53 as it is to be collected. Part of the supplied water evaporates and is condensed and recovered in the water condenser 51. Note that the water vapor contained in the exhaust air includes the fuel cell stack 2
It is considered that some of the water is caused by the reaction water accompanying the power generation reaction. The water condenser 51 is provided with a general-purpose heat exchanger (not shown), which is cooled by a fan to condense and recover water vapor in the exhaust air.

The water supply system 50 supplies the water in the tank 53 with the nozzle 5
5 is a closed system in which the water is supplied to the air manifold 45, and this water is collected by the water condenser 51 and returned to the tank 53. The water level in the tank 53 is constantly monitored by a water level sensor 56. A float type water level sensor was used. A heater 57 and an anti-freezing electromagnetic valve 58 are attached to the tank 53 so that the water in the tank 53 does not freeze in winter. An electromagnetic valve 60 is attached to a pipe connecting the water condenser 51 and the tank 53 to prevent water in the tank 53 from evaporating.

The water in the tank 53 is pumped by the pump device 100 to a nozzle 55 disposed in the air manifold 45, and is continuously or intermittently jetted from the nozzle 55 to the surface of the air electrode. This water is supplied to the air electrode of the fuel cell stack 2 and preferentially removes latent heat from the air, so that evaporation of water from the electrolyte membrane on the air electrode side is prevented. Therefore, the electrolyte membrane always maintains a uniform wet state without drying on the air electrode side. Further, the water supplied to the surface of the air electrode also removes heat from the air electrode itself and cools it, so that the temperature of the fuel cell stack 2 can be controlled. That is, the fuel cell stack 2 can be sufficiently cooled without adding a cooling water supply system to the fuel cell stack 2. The output of the pump device 100 is controlled in accordance with the temperature of the exhaust air detected by the exhaust temperature sensor 47, and the temperature of the fuel cell stack 2 is maintained at a desired temperature. It is preferable to provide an auxiliary pump 62 in the water supply system 50 in consideration of a case where the pump device 100 alone cannot supply sufficient water.

The load system 70 extracts the output of the fuel cell stack 2 to the outside and drives the motor 77. The load system 70 is provided with a relay 71 for a switch and a battery 75 as an auxiliary output source.
A rectifying diode 73 is interposed between the rectifying diode 73 and the rectifying diode 73.
The voltage of the fuel cell stack 2 itself is measured by the voltage sensor 76.
Is constantly monitored by Based on this monitoring result, the opening and closing of the hydrogen exhaust solenoid valve 33 is controlled by a control circuit (not shown).

Next, the pump device 100 of this embodiment will be described with reference to FIG. The pump device 100 shown in FIG. 2 includes a hydrogen gas introduction section 110 and a water introduction section 120.
Consists of The hydrogen gas inlet 110 is connected to the hydrogen supply path 2
0, and the water introduction unit 120 is in communication with the water supply path 61. The hydrogen gas introduction part 110 and the water introduction part 120 are separated by a partition 130, and the partition 130 has a bearing 131.
Is provided. A shaft 133 is rotatably fitted in the bearing 131. Hydrogen gas inlet 110 of shaft 133
A first blade 135 is attached to the side end, and a shaft 133 is provided.
The second blade 136 is attached to the end of the water inlet section 120 on the side of the second blade 136.

According to the pump device 100 configured as described above, the first blade 135 is rotated by flowing hydrogen through the hydrogen supply passage 20. This rotation is transmitted to the blade 136 by the shaft 133, and the blade 136 also rotates. The rotation of the blade 136 pressurizes the water in the water supply path 61,
It is sent to the nozzle 55 and jets out from this. When the flow of the hydrogen gas is intermittently performed, the driving of the pump device 100 is also intermittent. When the supply of water is required when the flow of hydrogen gas is stopped (fuel cell stack 2
(For example, when the temperature becomes abnormally high), the auxiliary pump 62 is driven.

FIG. 3 shows a pump device 200 according to another embodiment. The pump device 200 includes a first pump chamber 210 communicating with the hydrogen supply path 20 and a second pump chamber 220 communicating with the water supply path 61.
Is partitioned by an elastic membrane 230 formed of an elastically deformable material. A free piston 213 is inserted into the first pump chamber 210 so as to be movable in the left-right direction in the figure. Hydrogen gas has a small molecule, and thus may pass through the elastic film 230. The free piston 213 has a shielding effect on hydrogen gas. The pressure control valve 21 is controlled by a control device (not shown) to periodically change the hydrogen gas pressure in the hydrogen supply passage 20. Check valve 2 is provided between second pump chamber 220 and water supply passage 61.
21, 223 are provided.

According to the pump device 200 configured as described above, as the pressure in the hydrogen supply passage 20 is changed by the pressure regulating valve 21, the free piston 213 moves left and right in the figure. With the movement of the free piston 213, the elastic film 2
30 is deformed, and changes the volume of the second pump chamber 220. In accordance with such a change in the volume of the second pump chamber 220, the water in the water supply path 61 is pressurized, sent to the nozzle 55, and ejected from it.

The present invention is by no means limited to the description of the above-described embodiments and examples. Various modifications are included in the present invention without departing from the scope of the claims and within the scope of those skilled in the art.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a configuration of a fuel cell system according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of a pump device according to the embodiment.

FIG. 3 is a cross-sectional view illustrating a configuration of a pump device according to another embodiment.

[Explanation of symbols]

 Reference Signs List 1 fuel cell system 2 fuel cell stack 10 hydrogen supply system 50 water supply system 100, 200 pump device 135 first blade 136 second blade 210 first pump room 220 second pump room 230 elastic membrane

Claims (5)

[Claims] 1. A fuel cell stack, a fuel gas supply system for supplying fuel gas to the fuel cell stack, and a water supply means for supplying water pressurized by water pressurization means to the fuel cell stack. The fuel cell system according to claim 1, wherein the water pressurizing unit pressurizes the water using the pressure of the fuel gas. 2. The water supply system supplies water in a liquid state to an air electrode of the stack.
3. The fuel cell system according to item 1. 3. The water pressurizing means includes a first blade rotated by the fuel gas, and a second blade rotated by following the first blade. 3. The fuel cell system according to claim 1, wherein the blade is arranged in the water supply system, and pressurizes the water in the water supply system to supply the water to the fuel cell stack. 4. 4. The water pressurizing means includes a first pump chamber communicating with the fuel gas supply system, a second pump chamber communicating with the water supply system, and a pressure of the first pump chamber. 3. The fuel cell system according to claim 1, further comprising: means for changing the pressure, and means for transmitting a change in the pressure of the first pump chamber to the second pump chamber. 4. 5. A fuel cell stack, comprising: a fuel gas supply system for supplying a fuel gas to the fuel cell stack; and a water supply means for supplying water supplied by water supply means to the fuel cell stack. A fuel cell system, wherein the water feed means sends the water using the pressure of the fuel gas.