JP2002151115A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the amount of unreacted hydrogen exhausted from a fuel cell and suppress generation of stress or polymer membrane. SOLUTION: Hydrogen valves 505, 506 are installed on the hydrogen intake side and the hydrogen exhaust side, and the supply of hydrogen to the fuel cell 200 is adjusted with the hydrogen valves 505, 506 so as to intermittently conduct according to the consumption amount of the hydrogen of the fuel cell 200. Air valves (oxygen valves) 507, 508 are installed on the air (oxygen) intake side and the air exhaust side, and the supply of oxygen to the fuel cell 200 is adjusted with the air valves 507, 708 so as to intermittently conduct according to the intermittent supply of hydrogen.

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 comprising a fuel cell which generates electric energy by a chemical reaction between hydrogen and oxygen, and is applied to a moving body such as a vehicle, a ship and a portable generator. It is valid.

[0002]

2. Description of the Related Art As described above, a fuel cell generates electric power by chemically reacting hydrogen and oxygen.
It is necessary to supply hydrogen and oxygen (air) to the hydrogen path and the air path formed with the polymer film interposed therebetween according to the required amount of power. For this reason, even if more than necessary hydrogen is supplied to the fuel cell, unreacted hydrogen is released together with exhaust gas (such as water vapor or carbon dioxide).

[0003] Theoretically, the ratio of supplied hydrogen to oxygen is 2: 1. However, in the actual chemical reaction, not all of the hydrogen can be combined with oxygen, and not a little unreacted hydrogen is generated. Therefore, in general, the amount of hydrogen actually supplied to the fuel cell is set to be larger than the theoretical value in consideration of the amount of unreacted hydrogen. For this reason, it is difficult to reduce the amount of unreacted hydrogen discharged from the fuel cell.

[0004]

In order to reduce the amount of unreacted hydrogen discharged from the fuel cell, a valve is provided in a hydrogen passage for supplying hydrogen to the fuel cell. It is conceivable that the hydrogen-rich gas is retained in the gas to cause sufficient reaction of hydrogen to reduce the amount of unreacted hydrogen.

[0005] However, when the hydrogen valve is closed,
The hydrogen concentration decreases with the consumption of hydrogen in the fuel cell,
The hydrogen pressure in the hydrogen path in the fuel cell decreases. On the other hand, since air is continuously supplied to the air path side in the fuel cell, the pressure difference between the hydrogen path side and the air path side applied to the polymer membrane in the fuel cell increases. Then, when the hydrogen valve is opened and hydrogen is newly supplied to the hydrogen path side, the differential pressure applied to the polymer membrane returns to the original pressure. Therefore, by intermittently supplying hydrogen to the fuel cell by opening and closing the hydrogen valve, stress is repeatedly generated in the polymer membrane, which is not preferable in terms of durability.

In view of the above, it is an object of the present invention to reduce the amount of unreacted hydrogen discharged from a fuel cell and to suppress the generation of stress applied to a polymer membrane.

[0007]

According to the first aspect of the present invention, there is provided a fuel cell (20) for generating electric energy by a chemical reaction between hydrogen and oxygen.
0), a hydrogen supply means (100) for supplying hydrogen to the fuel cell (200), and an intermittent supply of hydrogen by the hydrogen supply means (100) according to the hydrogen consumption of the fuel cell (200). Hydrogen supply adjusting means (505, 5
06), the oxygen supply means (400) for supplying oxygen to the fuel cell (200), and the supply of oxygen from the oxygen supply means (400) intermittently in response to the intermittent supply of hydrogen. And oxygen supply adjusting means (507, 508).

Thus, when the hydrogen concentration in the fuel cell (200) is high, the hydrogen valves (505, 506) are closed and the hydrogen-rich gas is retained in the fuel cell (200) to sufficiently react hydrogen. Can be done. Thereby, the amount of unreacted hydrogen discharged from the fuel cell (200) can be reduced.

In addition, by intermittently supplying air (oxygen) in response to intermittent supply of hydrogen, the fuel cell (20
The change in the hydrogen concentration in 0) and the change in the air (oxygen) concentration can be made similar, and the pressure difference between the hydrogen path and the air path applied to the polymer membrane in the fuel cell (200) is kept constant. be able to. Thus, even if hydrogen is intermittently supplied to the fuel cell (200), it is possible to prevent the occurrence of stress on the polymer film and improve the durability of the polymer film.

[0010] The hydrogen supply adjusting means is provided in the hydrogen inflow passage (505a) and opens and closes the hydrogen inflow passage in the first hydrogen valve (505).
And a second hydrogen valve (506) provided in the hydrogen exhaust passage (506a) for opening and closing the hydrogen exhaust passage. The oxygen supply adjusting means is provided in the oxygen inlet passage (507a). The first oxygen valve (5
07) and a second oxygen valve (508) provided in the oxygen exhaust passage (508a) to open and close the oxygen exhaust passage.

According to the third aspect of the present invention, there is provided a residual hydrogen amount detecting means (601) for detecting the amount of hydrogen present in the fuel cell (200), and the first hydrogen valve (505).
And the second hydrogen valve (506) is provided with a hydrogen detecting means (6).
The first oxygen valve (507) is opened and closed based on the amount of hydrogen detected by the first hydrogen valve (505).
The second oxygen valve (508) is opened and closed in response to the opening and closing of
Are opened and closed in response to opening and closing of the second hydrogen valve (506).

The reference numerals in parentheses of the above-mentioned means indicate the correspondence with the concrete means described in the embodiments described later.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment to which the present invention is applied will be described below with reference to FIGS. In the present embodiment, the fuel cell system according to the present invention is applied to an electric vehicle (hereinafter, abbreviated as a vehicle).

FIG. 1 is a schematic diagram showing a fuel cell system according to this embodiment. As shown in FIG. 1, the fuel cell system according to the present embodiment includes a hydrogen production device (hydrogen supply unit) 100 and a fuel cell (FC stack) 200 surrounded by a dashed line.
And

The hydrogen production apparatus 100 produces (generates) a hydrogen-rich gas containing a large amount of hydrogen from a mixed solution of water and methanol (hereinafter, a methanol-mixed solution), and supplies the hydrogen-rich gas to an FC stack 200 described later. It is a hydrogen production device to supply. The hydrogen production apparatus 100 chemically reacts methanol vapor evaporated (vaporized) with water vapor by a hydrogen production fuel evaporator (hereinafter, evaporator) 110 for evaporating a methanol mixed solution,
The fuel cell system has a fuel reformer (hereinafter, referred to as a reformer) 120 for hydrogen production that reforms into hydrogen, carbon dioxide, and a small amount of carbon monoxide.

The evaporator 110 is configured such that a methanol mixed solution is sent from a methanol mixed solution tank 130 mounted on a vehicle and stores the methanol mixed solution by a first pump 131.

The FC stack 200 is used for the hydrogen production apparatus 10
0, the hydrogen-rich gas produced and the air (oxygen) undergo a chemical reaction to generate power. The fuel cell system according to the present embodiment is configured to drive the traveling electric motor M by the electric power generated by the FC stack 200. Since the catalytic function of the electrode catalyst in the FC stack 200 is easily reduced by carbon monoxide, in the present embodiment, carbon monoxide generated by oxidizing carbon monoxide generated in the reformer 120 to change it to carbon dioxide is used. The reducer 140 is provided in the hydrogen production apparatus 100.

The air blown to the FC stack 200 is
The air is humidified by the air humidifier 221. FC stack 20
Exhaust gas (water vapor, air, etc.) discharged from 0 is cooled by the dehumidifier 222 to remove and collect moisture. The moisture separated and removed by the dehumidifier 222 is returned to the air humidifier 221 via the condensed water return passage 223, and
It is reused for humidifying the air sent to the C stack 200.

FIG. 2 shows a schematic configuration of the FC stack 200. The FC stack 200 is a solid polymer electrolyte type fuel cell, and has a stack structure in which a plurality of cells as constituent units are stacked. As shown in FIG.
In each cell of the stack 200, a negative electrode side and a positive electrode side are separated with a polymer film 203 interposed therebetween, a hydrogen path 201 is formed on the negative electrode side, and an air path 202 is formed on the positive electrode side. Thereby, the hydrogen-rich gas is supplied to the negative electrode side, and air (oxygen) is supplied to the positive electrode side. Therefore, exhaust containing a large amount of water vapor is discharged from the positive electrode side, and unreacted hydrogen gas, carbon dioxide, and the like are discharged from the negative electrode side.

As shown in FIG. 1, a heating fuel (methanol in this embodiment) for heating the evaporator 110 is stored in a methanol fuel tank 300 mounted on a vehicle. The methanol (fuel) stored in the methanol fuel tank 300 is supplied to the evaporator 11 by the second pump 310.
Sent to 0. A portion of the methanol discharged from the second pump 310 is configured to be returned to the methanol fuel tank 300 via the methanol return passage 312. The methanol return passage 312 is opened and closed by a fuel return valve 311.

External air is sucked in by an air pump (oxygen supply means) 400, and is blown to the hydrogen production apparatus 100 (evaporator 110 and reformer 120) and the FC stack 200, and the combustion exhaust gas generated in the hydrogen production apparatus 100; The exhaust gas generated in the FC stack 200 is exhausted from exhaust passages 411 to 41.
4 and released into the atmosphere.

The blast air discharged from the air pump 400 is supplied to the hydrogen generator 1 by the first air distribution valve 501.
00 and the FC stack 200, and the distribution amount is adjusted. The air distributed to the hydrogen production apparatus 100 side by the first air distribution valve 501
By the air distribution valves 502, 503, the evaporator 110,
It is distributed to the reformer 120 and the carbon monoxide reducer 140, and the distribution amount is adjusted.

The methanol supplied from the methanol fuel tank 300 is supplied to the evaporator 110 and the reformer 120 by the methanol valve 504, and the supply amount is adjusted.

The hydrogen-rich gas supplied from the hydrogen production apparatus 100 is supplied to the FC stack 200 (negative electrode side) via a hydrogen inflow passage 505a, and is supplied to the hydrogen inflow passage 505a.
Is opened and closed by a first hydrogen valve 505. The hydrogen exhaust passage 506a of the FC stack 200 is connected to the second hydrogen valve 5
06. In the present embodiment, the exhaust gas from the hydrogen exhaust passage 506a on the negative electrode side is also discharged into the atmosphere similarly to the exhaust passage 414.

The blast air discharged from the air pump 400 and distributed to the FC stack 200 side by the first air distribution valve 501 is supplied to an air inflow passage (oxygen inflow passage) 507.
a to the FC stack 200 (positive electrode side). The air inflow passage 507a is opened and closed by a first air valve (first oxygen valve) 507. FC stack 20
0 air exhaust passage (oxygen exhaust passage) 508a on the positive electrode side
Is opened and closed by a second air valve (second oxygen valve) 508.

FIG. 3 is a control block diagram of the fuel cell system. As shown in FIGS. 1 and 3, the fuel cell system according to the present embodiment includes an FC stack 200 (negative electrode side).
A hydrogen sensor (residual hydrogen amount detection means) 601 for detecting the concentration of hydrogen (the amount of hydrogen) present in the gas sensor is provided. FIG.
As shown in (1), the detection signal of the hydrogen sensor 601 is input to an FC system controller (hereinafter, FCCU) 600 that controls the entire fuel cell system. And the first to third
Air distribution valves 501-503, methanol valve 50
4, first and second hydrogen valves 505 and 506, first and second hydrogen valves
The air valves 507 and 508 are controlled by the FCCU 600 based on a detection signal of the hydrogen sensor 601 and a detection signal of a sensor group S for detecting an operating state such as a temperature of the FC stack 200 and a load of a traveling electric motor.

Next, the operation of the first hydrogen valve 505 of the fuel cell system according to the present embodiment will be described with reference to FIG. FIG. 4 shows the amount of hydrogen detected by the hydrogen sensor 601 (residual hydrogen concentration in the FC stack), the opening / closing timing of the first and second hydrogen valves 505 and 506, the residual air concentration in the FC stack, Second air valve 50
It is a graph which shows the relationship of opening and closing timing of 7,508.

As shown in FIG. 4, the residual hydrogen concentration in the FC stack 200 is reduced to a first predetermined concentration (predetermined residual hydrogen concentration) d.
1 or less, the first hydrogen valve 5 on the hydrogen inflow side
05 is opened to supply hydrogen to the negative electrode side of the FC stack 200. Thereby, the hydrogen rich gas is supplied from the hydrogen supply facility 100 to the FC stack 200 via the hydrogen inflow passage 505a, and the hydrogen concentration in the FC stack 200 increases. At this time, the first air valve 507 on the air inflow side is also opened at the same time as the first hydrogen valve 505, and the FC stack 20 is opened.
Air (oxygen) is supplied to the positive electrode side of 0, and the air concentration in the FC stack 200 rises in the same manner as the hydrogen concentration.

Next, when the hydrogen concentration in the FC stack 200 becomes equal to or higher than the second predetermined concentration d2 which is higher than the first predetermined concentration d1, the first hydrogen valve 505 is closed to stop the supply of hydrogen to the FC stack 200. I do. At this time, the first air valve 507 is also closed at the same time as the first hydrogen valve 505,
The air supply to the FC stack 200 is stopped. In the FC stack 200, power is generated by a chemical reaction between hydrogen and oxygen, hydrogen and air (oxygen) are consumed, and the air concentration decreases along with the hydrogen concentration. Accordingly, FC
The power generation amount of the stack 200 gradually decreases.

Next, when the hydrogen concentration in the FC stack 200 becomes equal to or lower than the first predetermined concentration d1, the first hydrogen valve 505 is opened to supply a new hydrogen-rich gas from the hydrogen supply device 100 to the FC stack 200. I do. At the same time, the first air valve 507 is opened to supply fresh air to the FC stack 200.

On the other hand, the second hydrogen valve 506 on the hydrogen exhaust side
Operates such that the first hydrogen valve 505 opens earlier than when it opens (timing) and closes earlier than when the first hydrogen valve 505 closes (timing). The second air valve on the air exhaust side also operates at the same timing as the second hydrogen valve 508. Thereby, the first hydrogen valve 505
And the second hydrogen valve 506, the first air valve 507 and the second
The time when the air valves 508 are both open occurs, and the newly supplied hydrogen and air cause the FC stack 20 to open.
Residual gas existing on the negative electrode side and the positive electrode side within 0 can be quickly discharged.

Thereafter, as shown in FIG.
The first and second hydrogen valves 505 and 506 and the first and second air valves 507 and
08 is repeated to supply hydrogen and air (oxygen) to the FC stack 200 intermittently.

As described above, according to the fuel cell system of the present embodiment, the hydrogen rich gas is supplied to the FC stack 200 by opening and closing the hydrogen valves 505 and 506 provided in the hydrogen passage according to the hydrogen consumption in the FC stack 200. Can be supplied intermittently (intermittently). Thereby, FC stack 2
When the hydrogen concentration in the fuel cell 00 is high, the hydrogen valve 505,
506 is closed and the hydrogen rich gas is retained in the FC stack 200 so that hydrogen is sufficiently reacted.
If the hydrogen concentration in the gas becomes low, the hydrogen valve 50
5 and 506 are opened to discharge the residual gas from the inside of the FC stack 200 and to supply a new hydrogen-rich gas. Thereby, the amount of unreacted hydrogen discharged from the FC stack 200 can be reduced.

Further, in the fuel cell system of the present embodiment, the first and second air valves 507 and 508 are provided in the air passage, and are opened and closed at the same timing as the hydrogen valves 505 and 506, as shown in FIG. , FC stack 2
The change in the hydrogen concentration in the hydrogen path 201 in the air path 00 and the change in the air concentration in the air path 202 can be made similar. Thus, the pressure difference between the hydrogen path 201 and the air path 202 applied to the polymer film 203 in the FC stack 200 can be kept constant. Therefore, even if hydrogen is intermittently supplied to the FC stack 200, it is possible to prevent the occurrence of stress on the polymer film 203 due to the pressure difference between the hydrogen path 201 and the air path 202, and to reduce the durability of the polymer film 203. Can be improved.

(Other Embodiments) In the above embodiment, the hydrogen valves 505 and 506 and the air valves 507 and
08 are provided on each of the inflow side and the exhaust side of the FC stack 200, but the present invention is not limited to this, and the first hydrogen valve 505 and the first air valve 507 on the inflow side may be omitted. In this case, based on the hydrogen concentration in the FC stack 200 detected by the hydrogen sensor 601, the second hydrogen valve 506 on the hydrogen exhaust side is opened and closed to supply and exhaust hydrogen to the FC stack 200. The second air valve 508 on the air exhaust side is opened and closed during the FC stack 20
Supply / exhaust air (oxygen) to zero.

In the above embodiment, the hydrogen sensor 601 is used as the residual hydrogen concentration detecting means.
Although the hydrogen concentration in the FC stack 200 is directly detected by the above, the present invention is not limited thereto, and the hydrogen concentration in the FC stack 200 may be indirectly detected based on a physical quantity related to the hydrogen concentration in the FC stack 200. .

For example, since the amount of hydrogen consumed by the FC stack 200 is proportional to the amount of current output from the FC stack 200, a current detector (current detecting means) is used as a residual hydrogen concentration detecting means. By detecting the amount of electric power (current amount) output from the stack 200,
The configuration may be such that the residual hydrogen concentration (residual hydrogen amount) in the FC stack 200 is indirectly detected. Further, by using a pressure sensor (pressure detecting means) as the residual hydrogen concentration detecting means and detecting the gas pressure in the FC stack 200 (negative electrode side), the residual hydrogen concentration (residual hydrogen amount) in the FC stack 200 is indirectly detected. It may be configured to detect the error.

In the above embodiment, the present invention is applied to an electric vehicle. However, the present invention is not limited to this, and can be applied to a stationary type fuel cell system such as for home use.

In the above-described embodiment, the hydrogen supply device 100 is used as the hydrogen supply means for reforming a hydrocarbon-based fuel to produce a hydrogen-rich gas containing a large amount of hydrogen. The invention is not limited thereto, and a high-pressure hydrogen tank or a hydrogen tank using a hydrogen storage alloy that can supply pure hydrogen gas may be used as the hydrogen supply means.

In this case, since the hydrogen supplied to the FC stack 200 contains no impurities other than hydrogen, no carbon dioxide or the like remains in the FC stack 200.
Therefore, the first hydrogen valve 505 may be closed after the second hydrogen valve 506 is closed.

Incidentally, in a fuel cell system for an electric vehicle, hydrogen is supplied to the FC stack 200 under pressure, but in a stationary fuel cell system for home use, hydrogen is supplied to the FC stack 200 without pressurization. May be. In this case, it is desirable to open the first hydrogen valve 505 before opening the second hydrogen valve 506.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a fuel cell system according to the embodiment.

FIG. 2 is a schematic diagram of an FC stack.

FIG. 3 is a control block diagram of the fuel cell system according to the embodiment.

FIG. 4 shows the hydrogen concentration in the FC stack and the hydrogen valve 50
5 is a graph showing the relationship between the opening / closing timing of 5, 506, the air concentration in the FC stack, and the opening / closing timing of air valves 507, 508.

[Explanation of symbols]

100: hydrogen production apparatus (hydrogen supply means), 200: FC
Stack (fuel cell), 505 ... first hydrogen valve, 50
6 ... second hydrogen valve. 507: first air valve, 508
... Second air valve.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tomonori Imamura 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation (72) Inventor Tomohiro Saito 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Denso Corporation (72) Inventor Kunio Okamoto 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside DENSO Corporation (72) Inventor Hibiki Hattori 1, Toyota-cho, Toyota-shi, Aichi Prefecture F-term (reference) 5H026 AA06 5H027 AA06 MM04 MM09

Claims (3)

[Claims] 1. A fuel cell (200) for generating electric energy by a chemical reaction between hydrogen and oxygen; a hydrogen supply means (100) for supplying hydrogen to the fuel cell (200); and the fuel cell (200). Hydrogen supply adjusting means (505, 506) for adjusting the supply of hydrogen from the hydrogen supply means (100) intermittently according to the hydrogen consumption of the fuel cell; and supplying oxygen to the fuel cell (200). An oxygen supply means (400); and the oxygen supply means (40) in response to the intermittent supply of hydrogen.
A fuel cell system comprising: oxygen supply adjusting means (507, 508) for adjusting the supply of oxygen from 0) intermittently. 2. The hydrogen supply adjusting means is provided in a hydrogen inflow passage (505a) and opens and closes the hydrogen inflow passage with a first hydrogen valve (505) and a hydrogen exhaust passage (506).
a) a second hydrogen valve (506) provided in the oxygen inlet passage (507a) for opening and closing the hydrogen exhaust passage; and a first oxygen valve provided in the oxygen inlet passage (507a) for opening and closing the oxygen inlet passage. A valve (507) and an oxygen exhaust passage (508a),
A second oxygen valve (508) for opening and closing the oxygen exhaust passage
The fuel cell system according to claim 1, wherein 3. A fuel cell (200) further comprising: a residual hydrogen amount detecting means (601) for detecting an amount of hydrogen present in the fuel cell (200). The first hydrogen valve (505) and the second hydrogen valve (506) The first oxygen valve (507) is opened and closed according to the amount of hydrogen detected by the hydrogen detection means (601). The first oxygen valve (507) is opened and closed according to the opening and closing of the first hydrogen valve (505). 3. The fuel cell system according to claim 2, wherein the first and second valves are opened and closed in response to opening and closing of the second hydrogen valve.