JP2002008688A - Fuel cell power generation system - Google Patents

Abstract

(57) [Problem] To provide a fuel cell power generation system capable of collecting and storing hydrogen after purging and reusing the stored hydrogen. SOLUTION: In a fuel cell power generation system 1, a hydrogen storage means for collecting and storing hydrogen after purging foreign substances adhering to the surface of a hydrogen electrode 5 at an outlet side of a hydrogen passage 8 facing a hydrogen electrode 5 of a fuel cell 2. 22 are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Foreign matter such as water, carbon dioxide and nitrogen generated by an electrochemical reaction adheres to the hydrogen electrode surface of a fuel cell, and when this phenomenon occurs, the effective area of the hydrogen electrode surface decreases, so that the generated voltage is reduced. Decrease. Therefore, conventionally, a means has been adopted in which the amount of hydrogen supplied to the hydrogen passage is increased from that at the time of power generation, and foreign matter is purged by the hydrogen.

[0003]

The purging operation is performed relatively frequently, so that the amount of hydrogen used for the purging operation is increased. However, in the conventional system, the hydrogen after the purging is burned and treated as water. Therefore, there is a problem that a large amount of hydrogen is lost due to purging.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fuel cell power generation system in which hydrogen after purging is recovered and stored, and the stored hydrogen can be reused.

[0005] To achieve the above object, according to the present invention,
There is provided a fuel cell power generation system in which a hydrogen storage means for collecting and storing hydrogen after purging foreign substances adhering to the surface of the hydrogen electrode is disposed on an outlet side of a hydrogen passage facing a hydrogen electrode of the fuel cell.

With the above-described structure, it is possible to recover hydrogen after purging, greatly suppress an increase in the amount of hydrogen loss due to the purging, and store and reuse the recovered hydrogen. .

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A fuel cell power generation system 1 shown in FIG. 1 is mounted on, for example, an electric vehicle powered by a fuel cell 2.

The fuel cell 2 is of a solid polymer type. The cell 3 has a solid polymer electrolyte membrane 4, a hydrogen electrode (fuel electrode) 5 and an oxygen electrode (air electrode) 6 sandwiching the membrane 4. A pair of separators 7 respectively pressed against the outer surfaces of both electrodes 5 and 6, and a hydrogen passage 8 facing the hydrogen electrode 5 is formed by the separator 7 on the hydrogen electrode 5 side, and a separator 7 on the oxygen electrode 6 side by the separator 7 on the oxygen electrode 6 side. , An oxygen passage 9 facing the oxygen electrode 6 is formed.

A supply side of a high-pressure hydrogen tank 10 as a hydrogen supply source is connected to an inlet side of a hydrogen passage 8 in the fuel cell 2 through a supply pipe 11, and a supply side of an air supply device 12 as an oxygen supply source is supplied. Fuel cell 2 via line 13
Is connected to the inlet side of the oxygen passage 9 and its outlet side is open to the atmosphere. The first two-way valve V is sequentially connected to the supply line 11 on the high-pressure hydrogen tank 10 side from the tank 10 side.
1, a jet pump 14 and a humidifier 15 are provided. The jet pump 14 has a jet nozzle for passing high-pressure hydrogen and a suction port for applying a negative pressure generated by the passage of the high-pressure hydrogen. Further, the humidifier 15 humidifies the hydrogen to keep the solid polymer electrolyte membrane 4 in a wet state.

The outlet side of the hydrogen passage 8 in the fuel cell 2 is connected to the suction port side of the jet pump 14 via the first return line 16, and the first return line 16 is sequentially condensed from the fuel cell 2 side. A vessel 17 and a demister 18 are provided. The condenser 17 functions to liquefy water vapor contained in surplus hydrogen and the like discharged from the fuel cell 2. The demister 18 has a function of separating hydrogen and moisture and guiding the hydrogen to the jet pump 14 side and the moisture to the drain pipe 19 side. The first three-way valve 3V is located in the middle of the drain pipe 19
The first three-way valve 3V1 and the humidifier 15 are connected via a water supply line 21 having a pump 20.

On the outlet side of the hydrogen passage 8 of the fuel cell 2, in the embodiment, on the downstream side of the demister 18 of the first return pipe 16, foreign matter adhering to the surface of the hydrogen electrode 5, for example, hydrogen after purging water is recovered. A hydrogen storage means 22 is provided for storing hydrogen. The hydrogen storage means 22 stores the hydrogen stored therein at the inlet side of the hydrogen passage 8, in the embodiment, the first return pipe 1.
It also has a function of returning to the suction port side of the jet pump 14 through 6 and is configured as follows.

That is, the demister 18 of the first return line 16
Downstream is provided a second three-way valve 3V2,
A third three-way valve 3V is connected to the end of the branch line 23 extending from V2.
3 are connected. The fourth and fifth three-way valves 3V4 and 3V5 are connected to both terminals of the first and second introduction pipes 24 and 25 extending from the third three-way valve 3V3, respectively. Fourth three-way valve 3
The terminal of the first inlet / outlet line 26 extending from V4 is connected to a first tank 27 for hydrogen storage, and the first inlet / outlet line 26 is connected to the first three-way valve 3V4 side in the order of the first dehumidification. Container 28
And a flow meter 29 is provided. The terminal of the second inlet / outlet line 30 extending from the fifth three-way valve 3V5 is the second terminal for hydrogen storage.
A second dehumidifier 32 and a flow meter 33 are installed in the second inlet / outlet line 30 of the tank 31 in this order from the fifth three-way valve 3V5 side. In addition, the fourth and fifth three-way valves 3V4
Both terminals of the first and second outlet pipes 34 and 35 extending from 3V5 are connected in parallel with each other to a terminal of the second return pipe 36,
The second return line 36 is connected to the first return line 16 between the jet pump 14 and the second two-way valve 3V2. Second
A second two-way valve V2 is provided in the return line 36.

The first and second tanks 27 and 31 are made of stainless steel (JIS SUS304).
In these tank bodies, a powdery hydrogen storage alloy, in the embodiment, LaNi _3.96 Co _0.6 Al _0.44 alloy M
H is filled. This hydrogen storage alloy MH has characteristics such as storing hydrogen at 40 ° C. and releasing hydrogen at 85 ° C.

The first and second dehumidifiers 28 and 32 are provided to remove moisture from the occluded hydrogen. As the desiccant, those which can be regenerated by heating silica gel, zeolite, etc., in the embodiment, Zeolite ZEO is used. This zeolite ZEO adsorbs moisture at 40 ° C. and releases the adsorbed moisture as water vapor at 150 ° C.

The first and second tanks 27, 31 and the first,
Since the second dehumidifiers 28 and 32 have the above-mentioned temperature conditions in terms of function, they are provided with an electric heater and a cooling water cooler. It is as follows. That is, the power supply 37
In one of the two electric circuits 38, 39, the heaters 40, 41 of the first and second tanks 27, 31 are connected in parallel.
A first changeover switch 42 is provided at one of the parallel connection points 0 and 41. In the other electric circuit 39,
The heaters 43 and 44 of the second dehumidifiers 28 and 32 are connected in parallel, and a second switch 45 is provided at one of the parallel connection points of the heaters 43 and 44. Further, the radiator 46
And a cooling water pipe 48 having a pump 47 and a cooler 49 of the first tank 27 and a cooler 50 of the first dehumidifier 28 connected in series with the second tank 3 connected in series.
The first cooler 51 and the cooler 52 of the second dehumidifier 32 are connected in parallel, and the sixth and seventh three-way valves 3 are connected to both parallel connection points.
V6 and 3V7 are respectively installed.

Thermometers 53 and 54 for measuring the temperature in the tanks when storing and releasing hydrogen are provided in the first and second tanks 27 and 31, respectively.
And pressure gauges 55 and 56 for measuring the pressure in the tank at the time of storing and releasing hydrogen, respectively. The first and second dehumidifiers 28 and 32 are respectively provided with thermometers 57 and 58 for measuring the temperature at the time of moisture absorption / release.

Each flow meter 29, 33, each thermometer 53, 5
4, 57, 58 and pressure gauges 55, 56
Sent to the CU 59, and based on the information, the first and second
The changeover switches 42 and 45, the pump 47, the sixth and seventh three-way valves 3V6 and 3V7 are controlled. The ECU 59 also controls the first and second two-way valves V1 and V2, the first to fifth three-way valves 3V1 to 3V5, the pump 20 for supplying water to the humidifier 15, and the like.

As shown in FIG. 2, after the fuel cell power generation system 1 is started, in order to remove water adhering to the surface of the hydrogen electrode 5, a purge operation for supplying more hydrogen to the hydrogen passage 8 than during power generation is performed. Is performed intermittently. For example, when the hydrogen storage amount of the first tank 27 is full and that of the second tank 31 is empty, the zeolite ZEO of the second dehumidifier 32 is used.
At 40 ° C. adsorbs the hydrogen used for purging, that is, the moisture of the purge hydrogen, and the hydrogen storage alloy MH of the second tank 31 stores the purge hydrogen at 40 ° C.
The hydrogen storage alloy MH in the tank 27 releases hydrogen at 85 ° C. and the zeolite ZEO in the first dehumidifier 28
Releases steam at 0 ° C.

The adsorption of the purge hydrogen and the occlusion of the purge hydrogen and the release of the hydrogen and water vapor are alternately performed in the second tank 31 and the second dehumidifier 32 and in the first tank 27 and the first dehumidifier 28. Done.

The first tank 27 (or the second tank 3)
After the release of hydrogen from 1) and the first dehumidifier 28
After the release of water vapor from the (or second dehumidifier 32), the first tank 27 (or the second tank 31) and the first dehumidifier 28 (or the second dehumidifier 32) are cooled by the coolers 49, 50 (respectively). Or 51, 52) without being cooled, and after switching the tank, the first tank 27
If the temperatures of the (or the second tank 31) and the first dehumidifier 28 (or the second dehumidifier 32) exceed 40 ° C., the coolers 49 and 50 (or 51 and 52) may be used.
It is cooled below.

Next, the operation of the fuel cell power generation system 1 will be described with reference to FIGS. Before the start-up, the hydrogen storage amount of the first tank 27 is full, while
It is assumed that the tank 31 is empty.

When the start switch (not shown) is closed, the first two-way valve V1 is "open" and hydrogen in the high-pressure hydrogen tank 10 is supplied to the fuel cell 2 via the jet pump 14 and the humidifier 15, and simultaneously the air Since air is supplied from the supply device 12 to the fuel cell 2, power generation is started. 2nd 3-way valve 3V
2 is switched to the jet pump 14 side, the excess hydrogen discharged from the fuel cell 2 is sucked into the jet pump 14 via the condenser 17, the demister 18 and the second three-way valve 3V2, thereby circulating hydrogen. Is performed.

On the other hand, when the start switch is "closed", the sixth and seventh three-way valves 3V6 and 3V7 are switched to the second tank 31 and the second dehumidifier 32, respectively, and their temperatures are set to 40.
When the temperature exceeds ℃, the pump 47 and the radiator 46 operate to start cooling the second tank 31 and the second dehumidifier 32. When the temperature of each of the second tank 31 and the second dehumidifier 32 drops below 40 ° C., the operations of the pump 47 and the radiator 46 are stopped, and the cooling of the second tank 31 and the second dehumidifier 32 ends. When the temperatures of the second tank 31 and the second dehumidifier 32 are 40 ° C. or less from the beginning, the cooling is not performed. The first and second changeover switches 42 and 45 are connected to the first tank 27 and the first dehumidifier 28.
Side, the first tank 27 and the first
Heating of the dehumidifier 28 is started, and this heating will be described later.

The cell voltage of the fuel cell 2 is measured when the hydrogen circulation is performed and the temperature of the second tank 31 and the second dehumidifier 32 is 40 ° C. or less, and the cell voltage is set to a specified value, for example, 0.80 V (cell In this case, the purge operation for the hydrogen electrode 5 is performed. That is, by adjusting the opening of the first two-way valve V1, more hydrogen is supplied to the hydrogen passage 8 of the fuel cell 2 than at the time of power generation to remove water from the surface of the hydrogen electrode 5, and at the same time, the second, third Then, the fifth three-way valve 3V2, 3V3, 3V5 is switched to the second tank 31 side to store the purge hydrogen in the second tank 31 via the second dehumidifier 32. If the cell voltage is equal to or higher than the specified value, the power generation of the fuel cell 2 is continued.

When the removal of water from the surface of the hydrogen electrode 5 is completed, it is determined whether or not power generation is stopped.
The mode shifts to a stop mode to be described later. On the other hand, when the power generation is continued, it is determined whether or not the second tank 31 is full. If not full, the opening of the first two-way valve V1 is adjusted to that at the time of power generation, and the second three-way valve 3V2 is
Side, power generation and hydrogen circulation are performed, and then the same purging operation as described above is repeatedly performed. When the temperature rises and exceeds 40 ° C. due to the occlusion of hydrogen in the second tank 31 and the adsorption of moisture in the second dehumidifier 32, the pump 47 and the radiator 46 operate to operate the second tank 31 and the second dehumidifier. 32 is started. Second tank 31
When the temperature of the second dehumidifier 32 and the temperature of the second dehumidifier 32 drop below 40 ° C., respectively, the operations of the pump 47 and the radiator 46 stop. The case of the full state will be described later.

As described above, the first and second changeover switches 4
By switching to the first tank 27 and the first dehumidifier 28 side, heating of these 27 and 28 is started,
The temperature of the first tank 27 becomes 85 ° C. and the first dehumidifier 28
When the temperature reaches 150 ° C., the first tank 27
And the first dehumidifier 28 is kept in its high temperature state.

When the fourth three-way valve 3V4 is switched to the jet pump 14, the second two-way valve V2 is simultaneously opened and
Hydrogen is released from the first tank 27 and the first dehumidifier 2
Since the steam is released from 8, the humidified hydrogen is supplied to the jet pump 14 and used for power generation.

When the first tank 27 is empty, the second two-way valve V2 is closed and the fourth three-way valve 3V4 is closed.
It is switched to the three-way valve 3V3 side.

Next, the same operation as described above is performed when the first tank 27 is empty and the second tank 31 is full. That is, in FIG.
The operation proceeds in a state where the dehumidifier 28, the second tank 31, and the second dehumidifier 32 are alternately exchanged.

Next, with reference to FIG. 4, description will be given of a case where the mode is shifted to the stop mode.

First, the first two-way valve V1 is closed, and then the first tank 27 is connected to the supply line 11 and the first return line 1.
It is determined whether or not the residual hydrogen in the hydrogen circulation system including No. 6 can be stored.

When the storage is possible, the second, third, and fourth three-way valves 3V2 to 3V4 are switched to the first tank 27 side, and the residual hydrogen is stored in the first tank 27. And
It is determined whether or not the pressure in the hydrogen circulation system is the atmospheric pressure. If the pressure is the atmospheric pressure, the start switch is opened and the stop mode ends. On the other hand, if the pressure in the hydrogen circulation system exceeds the atmospheric pressure, the occlusion is continued.

If the first tank 27 cannot store the residual hydrogen, the second, third, and fifth three-way valves 3V2, 3V3, 3
V5 is switched to the second tank 31 side and residual hydrogen is
It is stored in the tank 31. Then, it is determined whether the pressure in the hydrogen circulation system is the atmospheric pressure or not. If the pressure is the atmospheric pressure, the start switch is opened and the stop mode ends. On the other hand, if the pressure in the hydrogen circulation system exceeds the atmospheric pressure, the occlusion is continued.

The capacities of the first and second tanks 27 and 31 are set so as to be able to occlude residual hydrogen in the hydrogen circulation system even when the tanks are full as described above.

As described above, the first and second tanks 27, 31
When the storage and release of purge hydrogen are performed at the same time by using, the amount of hydrogen storage alloy can be reduced and the weight of the system can be reduced as compared with the case where only one tank is used. Further, when power generation is stopped, residual hydrogen in the hydrogen circulation system can be occluded in the first or second tanks 27 and 31, and waste of hydrogen can be reduced.

[0036]

According to the first aspect of the present invention, hydrogen after purging is recovered, the increase in the amount of hydrogen loss due to the purging is greatly suppressed, and the recovered hydrogen is stored and reused. A fuel cell power generation system capable of performing the above can be provided.

According to the second aspect of the present invention, in addition to the above effects, it is possible to provide a fuel cell power generation system capable of using hydrogen after purge as fuel.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a fuel cell power generation system.

FIG. 2 is a graph showing the relationship among time, the flow rate of purge hydrogen, the temperature of a tank and a dehumidifier, and the amount of hydrogen in a tank.

FIG. 3 is a flowchart of an operation mode.

FIG. 4 is a flowchart of a stop mode.

[Description of Signs] 1 fuel cell power generation system 2 fuel cell 5 hydrogen electrode 8 hydrogen passage 22 hydrogen passage 22 hydrogen Storage means 27 First tank 31 Second tank 40, 41 Heater 49-52 Cooler

Claims (2)

[Claims] At the outlet side of a hydrogen passage (8) facing a hydrogen electrode (5) of a fuel cell (2), hydrogen after purging foreign substances adhering to the surface of the hydrogen electrode (5) is collected and stored. A fuel cell power generation system comprising a hydrogen storage means (22). 2. The fuel cell power generation system according to claim 1, wherein said hydrogen storage means (22) has a function of returning hydrogen stored in said means (22) to an inlet side of said hydrogen passage (8).