JP2000260458A - Fuel cell system and fuel cell automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system for which stack humidifying parts for humidifying a hydrogen-containing fuel gas and the introduced air does not need to be expanded in order to keep water saturated in a solid high-polymer electrolyte film. SOLUTION: This PEFC fuel cell system A is provided with: a fuel cell stack 1 composed by alternately stacking unit cells each formed by tightly arranging a fuel electrode and an oxidizer electrode on respective surfaces of a solid high-polymer electrolyte film, and separators; and stack humidifying parts 2, 3 for humidifying the introduced air and a hydrogen-containing fuel gas in order to keep water saturated in the solid high-polymer electrolyte film; and performs power generation by means of an electrochemical reaction between the electrodes of each of the unit cells. In this case, an oxygen enrichment device 4 employing a pressure swing adsorption method for performing gas separation by repeating an adsorption process and a removal process is added to the system, and the oxygen-enriched air increased in oxygen concentration by the oxygen enrichment device B is fed to an air introduction port 28 of the stack humidifying part 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a fuel cell system suitable for mounting on an automobile.

[0002]

2. Description of the Related Art An electric vehicle equipped with a fuel cell system (see FIG. 6) for generating electricity by causing an electrochemical reaction between hydrogen and oxygen contained in introduced air has been known.

[0003]

The amount of power generated by the fuel cell is
It can be increased by increasing the introduction amount by increasing the total pressure of the air supplied to the oxidant electrode. However, in order to increase the total pressure of the air, it is necessary to increase the operating pressure of the air pump that sucks in air, which causes an increase in noise and, for example, two-stage pressurization with a turbo and a supercharger is required, and This causes an increase in the size of the pump.

When the amount of air supplied to the oxidizing agent electrode is increased, the size of the stack humidifier for humidifying the fuel gas or air is increased in order to maintain the saturated water content of the solid polymer electrolyte membrane frequently used in fuel cells. There is a need.

A first object of the present invention is to provide a fuel cell system capable of increasing the amount of power generation without increasing the size of an air pump. A second object of the present invention is to provide a fuel cell system which does not require a large stack humidifier for humidifying a fuel gas containing hydrogen and introduced air in order to maintain the saturated water content of the solid polymer electrolyte membrane. is there. A third object of the present invention is to provide a fuel cell system suitable for mounting on an automobile.

[0006]

According to a first aspect of the present invention, there is provided a fuel cell system comprising: a fuel cell which performs an electrochemical reaction between hydrogen and oxygen contained in introduced air to generate electric power; An oxygen enrichment device employing a pressure swing adsorption method for performing gas separation by repeating the above process is added, and oxygen-enriched air having an increased oxygen concentration by the oxygen enrichment device is supplied to the fuel cell.

For this reason, the capacity of the fuel cell is increased,
The power generation amount of the fuel cell can be greatly increased without increasing the amount of air introduced. Since the oxygen enrichment apparatus employs the pressure swing adsorption method, the oxygen concentration can be significantly increased, and the configuration is simple and the cost is low.

(Claim 2) Between a single cell in which a fuel electrode and an oxidant electrode are disposed in close contact with each surface of a solid polymer electrolyte membrane having H ⁺ ion conductivity, and a fuel electrode and an oxidant electrode A fuel cell stack in which gas-impermeable and conductive separators having a fuel gas flow path and an oxidizing gas flow path formed thereon are alternately stacked, and hydrogen is maintained to maintain the saturated water content of the solid polymer electrolyte membrane. And a stack humidifying unit for humidifying the fuel gas and the introduced air, the pressure for performing gas separation by repeating the adsorption process and the desorption process in the fuel cell system that generates power by an electrochemical reaction generated between the electrodes of the single cell. An oxygen enrichment device employing a swing adsorption method is added, and oxygen-enriched air having an increased oxygen concentration by the oxygen enrichment device is supplied to an air inlet of a stack humidifier.

Therefore, the fuel cell system can increase the power generation amount of the fuel cell stack without increasing the amount of air supplied to the air inlet of the stack humidifier.
Therefore, it is not necessary to increase the amount of air supplied to the air inlet of the stack humidifying unit, and it is necessary to increase the size of the stack humidifying unit (the side that humidifies the introduced air) for maintaining the saturated water content of the solid polymer electrolyte membrane. Absent.

In the oxygen enrichment apparatus, air sucked by an air pump is supplied to an adsorption column filled with an adsorbent for selectively adsorbing nitrogen in air under pressure to adsorb nitrogen. The adsorption step of adsorbing the adsorbent and the desorption step of regenerating the adsorbent by depressurizing the inside of the adsorption cylinder to desorb the nitrogen adsorbed on the adsorbent are performed alternately.

For this reason, the fuel cell system of the first and second aspects to which the configuration of the third aspect is added increases the power generation amount of the fuel cell and the fuel cell stack without increasing the total pressure of the air supplied to the fuel cell. be able to. Since there is no need to attach a turbocharger or a supercharger to the air pump, the size of the air pump is not increased, and the noise does not increase.

According to a fourth aspect of the present invention, there is provided an oxygen enrichment apparatus comprising: an air pump for sucking air; first and second adsorption cylinders in which an adsorbent for selectively adsorbing nitrogen in air under pressure is filled. In the adsorption step, the discharge port of the air pump communicates with one end of the first adsorption cylinder, and one end of the second adsorption cylinder communicates with the atmosphere. In the desorption step, one end of the first adsorption cylinder And a four-way switching valve for communicating the discharge port of the air pump with one end of the second adsorption cylinder, and a position between the other end of the first adsorption cylinder and the air introduction port of the stack humidifier. A first solenoid valve that opens during the adsorption stroke and closes during the desorption stroke, and is located between the other end of the second adsorption cylinder and the air inlet of the stack humidifier, and closes during the adsorption stroke. A second solenoid valve that opens during the desorption process and a purge pipe that connects the other end of the first and second adsorption cylinders are disposed in a purge pipe. And a purge orifice for introducing a portion of the oxygen-enriched air to the adsorption column in step.

For this reason, the fuel cell system according to the first and second aspects to which the configuration according to the fourth aspect is added has a simple configuration without increasing the total pressure of the air supplied to the fuel cell or the air inlet of the stack humidifier. Therefore, the power generation amount of the fuel cell or the fuel cell stack can be increased at low cost.

The oxygen-enriching device has an oxygen-concentration holding means, and keeps the oxygen-enriched air supplied to the fuel cell or the fuel cell stack at a substantially constant oxygen concentration. For this reason, it is possible to prevent fluctuations in the power generation amount of the fuel cell or the fuel cell stack, and to stably maintain a high power generation amount. The oxygen concentration holding means is, for example, an increase in the number of adsorption cylinders, installation of a chamber for storing oxygen-enriched air, and the like.

(Claim 6) The power generation amount of the fuel cell or the fuel cell stack can be greatly increased without significantly increasing the cost and the volume, and is excellent in mounting on an automobile. Specifically, the traveling motor can have a high output (improved acceleration), and the electrical components can be used with a margin.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention (Claim 1,
2, 3, 4, and 6) will be described with reference to FIGS. The PEFC type fuel cell system A shown in FIG. 1 includes a fuel cell stack 1, stack humidifiers 2, 3 and an oxygen enrichment device 4, and is assembled to an automobile 5.

As shown in FIG. 4, the fuel cell stack 1
A single cell 10 in which a fuel electrode 12 and an oxidant electrode 13 are arranged in close contact with each surface of a solid polymer electrolyte membrane 11 (see FIG. 3).
And separators 14 and 15 are alternately laminated via gaskets 16 and 17.

In order to satisfy corrosion resistance, hydrogen embrittlement resistance, gas impermeability, and conductivity,
Uses graphite plate. And the fuel electrode 12
A fuel gas passage and an oxidizing gas passage (concave groove) are formed on the side facing the oxidant electrode 13.

The solid polymer electrolyte membrane 11 (0.1 m thick)
m) is a sheet-like polymer membrane having a proton exchange group in the molecule. The solid polymer electrolyte membrane 11 has a low electric resistance of 20 Ω · cm or less at room temperature due to saturated water content, and functions as a proton conductive electrolyte.

The fuel electrode 12 (anode) is a sheet-like electrode closely adhered to one end surface of the solid polymer electrolyte membrane 11. The oxidant electrode 13 (cathode) is a sheet-like electrode adhered to the other end surface of the solid polymer electrolyte membrane 11. The fuel electrode 12 and the oxidant electrode 13
Upon receiving the supply of the fuel gas and the oxidizing gas, DC power is generated by the following chemical reaction.

The hydrogen supplied to the fuel electrode 12 is dissociated into hydrogen ions and electrons by a catalytic reaction. Hydrogen ions move in the solid polymer electrolyte membrane 11 and react with oxygen on the oxidant electrode 13 to generate water. The electrons flow through the external circuit to the oxidant electrode 13 and contribute to the reaction between hydrogen ions and oxygen. The flow of electrons in the external circuit is extracted as electric power.

In order to make the solid polymer electrolyte membrane 11 show H ⁺ ion conductivity, it is necessary to make the membrane saturated with water. Therefore, in the PEFC type fuel cell system A, a stack humidifier is provided in front of the fuel cell stack 1. Parts 2 and 3 are arranged to humidify the hydrogen and oxygen enriched air.

The PEFC fuel cell system A of the present embodiment
In the first embodiment, water contained in exhaust gas passing through the fuel cell stack 1 is condensed and collected by the condensed water trap 21.
Then, the collected water is supplied to the stack humidifying section 2 via the water circulation pump 22, and is reused. On the other hand, hydrogen contained in the exhaust gas that has passed through the fuel cell stack 1 is sent to the fuel cell stack 1 via the stack humidifier 3 by the hydrogen circulation pump 31. Note that the amount consumed in the fuel cell stack 1 is supplied from the hydrogen storage tank 9 via the pressure regulating valve 91. In addition, 23 is a cooling water pump, 24 and 25 are switching valves, and 26 is a radiator.

The oxygen enrichment device 4 includes an air pump 41,
Adsorption cylinders 42 and 43, a four-way switching valve 44, a solenoid valve 45,
46 and a purge orifice 48 disposed in a purge pipe 47 for selectively adsorbing nitrogen to increase the oxygen concentration.

The air pump 41 sucks air from the atmosphere to increase the pressure to about 0.5 kgf / cm ² . Suction cylinder 4
Reference numerals 2 and 43 each have a cylindrical shape and enclose a zeolite that selectively adsorbs nitrogen in air under pressure.

The four-way switching valve 44 connects the discharge port 411 of the air pump 41 and one end 421 of the suction tube 42 during the suction stroke shown in FIGS. 431 is communicated to the atmosphere. In addition, in the desorption process shown in FIG.
Is communicated to the atmosphere, and the discharge port 411 of the air pump 41 and one end 431 of the adsorption cylinder 43 are communicated.

The solenoid valve 45 is connected to the other end 422 of the suction cylinder 42.
And the valve is opened in the suction stroke (several minutes) shown in FIG. 1 and FIG. 2 (a) and located in the pipe 27 connecting the air introduction port 28 of the stack humidifier 2. The valve is closed in the indicated desorption stroke (several minutes).

The solenoid valve 46 is connected to the other end 432 of the suction tube 43.
2 and the air inlet 28 of the stack humidifier 2, and is closed in the adsorption process shown in FIGS. 1 and 2A, and in the desorption process shown in FIG. 2B. Open the valve.

The purge orifice 48 is provided with the adsorption cylinders 42, 4
3 is disposed in a purge 47 pipe connecting between the other ends 422 and 432, and a part of the oxygen-enriched air is introduced into the adsorption column 42 in the desorption process shown in FIG.

The air pump 41 and the four-way switching valve 4
4. The energization of the solenoid valves 45 and 46 is controlled by a control device (not shown).

The electric power obtained by the PEFC type fuel cell system A is supplied to a running motor 52 for driving the tires via a motor controller 51 and charges an ultracapacitor 53 disposed in the rear luggage space. The other part of the PEFC fuel cell system A is provided in the space 54 below the rear seat (see FIG. 5).

Next, advantages of the PEFC type fuel cell system A of this embodiment will be described. [A] The PEFC fuel cell system A uses the oxygen-enriched air whose oxygen concentration has been increased by the oxygen enrichment device 4 employing the pressure swing adsorption method, and the saturated water content of the solid polymer electrolyte membrane 11 of the fuel cell stack 1. It is supplied to the air inlet 28 of the stack humidifying section 2 installed for maintenance.

As a result, the amount of power generated by the fuel cell stack 1 can be significantly increased without increasing the amount of air supplied to the stack humidifier 2. Specifically, in the system of the present embodiment, the output of the fuel cell stack 1 having a normal output of 50 kW can be increased to 60 kW by increasing the air having an oxygen concentration of 20.9% to 25%.
Since the amount of air supplied to the stack humidifier 2 is not increased, it is not necessary to increase the size of the stack humidifier 2.

[I] The PEFC fuel cell system A
The power generation amount of the fuel cell stack 1 is increased without increasing the total pressure of the air supplied to the fuel cell stack 1. For this reason, since it is not necessary to attach a turbo or a supercharger to the air pump 41, the size of the air pump 41 is not increased and the noise does not increase. In order to increase the power generation amount of the fuel cell stack 1 by the same degree by increasing the total pressure of the air, it is necessary to attach a turbo and a supercharger to about 2.0 kgf / cm ² . This causes a significant increase in noise.

[U] Since oxygen is enriched by the oxygen enrichment apparatus 4 employing the pressure swing adsorption method, the following advantages are provided. The oxygen enrichment device 4 is inexpensive and easy to maintain.・ Zeolite (adsorbent) can be used semi-permanently. -The oxygen enrichment device 4 is safe and highly reliable. -The oxygen enrichment device 4 is not restricted by laws and regulations such as the High Pressure Gas Control Law.

[E] To increase the power generation amount of the fuel cell stack 1 without enriching the oxygen, the fuel cell stack 1
It is necessary to increase the size of the fuel cell itself, increase the size of the stack humidifying section 2, and increase the size of the air pump 41, and it is inevitable that the cost, the occupied area, and the noise increase. However, the PEFC fuel cell system A
Indicates a slight increase in the occupied volume (the presence of the adsorption cylinders 42, 43, the four-way switching valve 44, the solenoid valves 45, 46, the purge pipe 47, and the purge orifice 48) and a slight increase in power consumption (the four-way switching valve 44). And for controlling the electromagnetic valves 45 and 46) alone, it is possible to greatly increase the power generation amount of the fuel cell stack 1.

The present invention includes the following embodiments in addition to the above embodiment. a. The oxygen concentration holding means for keeping the oxygen concentration of the oxygen-enriched air supplied to the stack humidifying section 2 substantially constant includes the following (corresponding to claim 5). -Increase the number of suction cylinders to, for example, three. -A chamber for storing oxygen-enriched air is provided at a stage preceding the stack humidifying section 2. Increase the rotation speed of the air pump 41 at or immediately after the switching of the suction cylinder.

If the oxygen concentration holding means is added, the power generation amount of the fuel cell stack 1 can be prevented from fluctuating at the time of switching the adsorption cylinder or immediately after the switching, and a high power generation amount can be maintained stably. I can run.

B. Hydrogen may be generated by reforming methanol.

[Brief description of the drawings]

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

FIG. 2 is an operation explanatory diagram of an oxygen enrichment device used in the PEFC type fuel cell system in an adsorption step (a) and a desorption step (b).

FIG. 3 is an explanatory diagram of a single cell of a fuel cell stack used in the PEFC type fuel cell system.

FIG. 4 is an explanatory view for assembling a fuel cell stack used in the PEFC type fuel cell system.

FIG. 5 is an explanatory diagram of a fuel cell vehicle using the PEFC type fuel cell system.

FIG. 6 is a configuration diagram of a fuel cell system according to a conventional technique.

[Explanation of symbols]

 A PEFC type fuel cell system (fuel cell system) 1 fuel cell stack 2, 3 stack humidifier 4 oxygen enrichment device 10 single cell 11 solid polymer electrolyte membrane 12 fuel electrode 13 oxidant electrode 14, 15 separator 28 air inlet 41 air pump 42 adsorption cylinder (first adsorption cylinder) 43 adsorption cylinder (second adsorption cylinder) 44 four-way switching valve 45 solenoid valve (first solenoid valve) 46 solenoid valve (second solenoid valve) 47 purge pipe 48 Purge orifice 411 Discharge port

Continued on front page F-term (reference) 4D012 CA05 CB16 CD07 CE01 CF05 CG01 CH10 CJ03 CJ05 CJ07 CK02 CK03 5H026 AA06 CC03 CC08 5H027 AA06 BA14 BA19 BC06 CC06 MM01 MM04

Claims (6)

[Claims] 1. A fuel cell, which generates electricity by electrochemically reacting hydrogen and oxygen contained in introduced air, using a pressure swing adsorption method in which gas is separated by repeating an adsorption step and a desorption step. A fuel cell system, further comprising adding an enrichment device, and supplying oxygen-enriched air having an oxygen concentration increased by the oxygen enrichment device to the fuel cell. 2. A fuel cell between the fuel electrode and the oxidant electrode, and a single cell in which a fuel electrode and an oxidant electrode are disposed in close contact with each surface of a solid polymer electrolyte membrane having H ⁺ ion conductivity. A fuel cell stack formed by alternately stacking gas-impermeable and conductive separators having formed gas channels and oxidizing gas channels, and hydrogen to maintain saturated water content of the solid polymer electrolyte membrane. A fuel cell system comprising a stack humidifier for humidifying the fuel gas and the introduced air, wherein the fuel cell system generates power by an electrochemical reaction generated between the electrodes of the single cell, wherein a pressure at which gas is separated by repeating an adsorption step and a desorption step. An oxygen enrichment device employing a swing adsorption method is added, and oxygen-enriched air having an increased oxygen concentration by the oxygen enrichment device is supplied to an air inlet of the stack humidifier. Fuel cell system. 3. The oxygen enrichment device supplies air sucked by an air pump to an adsorption column filled with an adsorbent that selectively adsorbs nitrogen in air under pressure to reduce the nitrogen into the adsorbent. And a desorption step of depressurizing the inside of the adsorption cylinder to desorb nitrogen adsorbed on the adsorbent and regenerating the adsorbent is performed alternately. Item 3. The fuel cell system according to Item 2. 4. An oxygen enrichment device, comprising: an air pump for sucking air; first and second adsorption cylinders enclosing an adsorbent for selectively adsorbing nitrogen in air under pressure; Then, the discharge port of the air pump communicates with one end of the first adsorption cylinder, and one end of the second adsorption cylinder communicates with the atmosphere. During the desorption process, one end of the first adsorption cylinder A four-way switching valve having an end communicating with the atmosphere and a communication port between the discharge port of the air pump and one end of the second adsorption cylinder; and an air introduction port of the other end of the first adsorption cylinder and the stack humidifier. A first solenoid valve that opens during the adsorption stroke and closes during the desorption stroke, and is located between the other end of the second adsorption cylinder and the air inlet of the stack humidifier. A second solenoid valve that closes in the adsorption stroke and opens in the desorption stroke, and the other end of the first and second adsorption cylinders 3. The fuel cell system according to claim 1, further comprising a purge orifice disposed in a purge pipe connected thereto and introducing a part of oxygen-enriched air into the adsorption column during a desorption process. 5. The oxygen-enriching device according to claim 1, further comprising an oxygen-concentration holding unit for maintaining an oxygen concentration of the oxygen-enriched air supplied to the fuel cell or the fuel cell stack substantially constant. The fuel cell system according to any one of claims 1 to 4. 6. A fuel cell vehicle equipped with the fuel cell system according to claim 1.