JP3358820B2 - Hydrogen booster and fuel cell using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hydrogen booster and a fuel cell using the same.

[0002]

2. Description of the Related Art Fuel cells do not need to use fossil fuels, which have a problem of resource depletion, and generate almost no noise.
Since it has excellent features such as an extremely high energy recovery efficiency as compared with other energy engines, it is used as a relatively small power plant, for example, in a building unit or a factory unit. In recent years, this fuel cell has been used as a power source for a motor that operates in place of a vehicle-mounted internal combustion engine,
It has been considered that a vehicle or the like is driven by this motor. In this case, it is important to recycle as much as possible the substances generated by the reaction. It is desirable that the size is as small as possible. From such a point, a fuel cell using an ion exchange membrane, in particular, a solid polymer electrolyte membrane fuel cell has attracted attention.

Here, as an example, the basic structure of a polymer electrolyte membrane fuel cell body will be described with reference to FIG.
As shown in the figure, a battery main body 01 is configured by joining gas diffusion electrodes 03A and 03B to both sides of a solid polymer electrolyte membrane 02. The joined body is provided on both sides of the solid polymer electrolyte membrane 02 with gas diffusion electrodes 03A and 03A.
It is manufactured by hot pressing or the like after combining B. The gas diffusion electrodes 03A and 03B are formed by bonding reaction films 04A and 04B and gas diffusion films 05A and 05B, respectively.
The surface of 4B is in contact. Therefore, the battery reaction mainly occurs at the contact surface between the electrolyte membrane 02 and the reaction membranes 04A and 04B. Further, on the surface of the gas diffusion electrode 03A,
A gas separator having an oxygen supply groove 06a is joined to a gas separator 07 having a hydrogen supply groove 07a on the surface of the other gas diffusion electrode 03B, and constitutes an oxygen electrode and a hydrogen electrode.

When the oxygen supply groove 06a and the hydrogen supply groove 07a supply oxygen and hydrogen, respectively, oxygen and hydrogen are supplied to the reaction films 04A and 04B via the gas diffusion films 05A and 05B, respectively. Reaction membrane 04A, 04B
The following reaction occurs at the interface between the electrolyte membrane 02 and the electrolyte. Interface of the reaction film 04A: O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O Interface of the reaction film 04B: 2H ₂ → 4H ⁺ + 4e ⁻ Here, although 4H ⁺ flows from the hydrogen electrode to the oxygen electrode through the electrolyte film 02, 4e ^- is will flow from the hydrogen electrode to the oxygen electrode through the load 08, electrical energy is obtained.

[0005]

In such a fuel cell,
Supplying primarily hydrogen feed reformed gas obtained by reforming methanol in the hydrogen electrode, the hydrogen feed reformed gas other hydrogen, there is a problem in that CO ₂ and CO are contained.
That is, in order to improve the performance by increasing the output density of the fuel cell, it is effective to remove the impurity gas such as CO in the hydrogen source reformed gas and to improve the partial pressure of the hydrogen gas.

[0006] In view of such circumstances, an object of the present invention is to provide a device capable of increasing the hydrogen pressure and a fuel cell using the same.

[0007]

According to the present invention, there is provided a hydrogen booster comprising: a carbon monoxide reducing means for reducing carbon monoxide from a methanol reformed gas; A joined body formed by joining the molecular electrolyte membranes therebetween, a power supply for applying a voltage to two gas diffusion electrodes of the joined body, and a hydrogen-containing gas supplied to the gas diffusion electrode connected to the positive electrode of the power supply And a hydrogen discharge system for extracting high-pressure hydrogen gas of 10 atm or less from the gas diffusion electrode connected to the negative electrode of the power supply. Also, the fuel cell according to the present invention
A fuel cell for generating electricity by supplying hydrogen gas and oxygen or air to hydrogen electrodes and oxygen electrodes on both sides of a joined body formed by joining a solid polymer electrolyte membrane between two gas diffusion electrodes, The hydrogen gas supply line to the poles
And a high-pressure hydrogen gas of 10 atm or less is supplied to the hydrogen electrode from a hydrogen discharge line of the hydrogen pressure increasing device.

[0008]

When a voltage is applied to the two gas diffusion electrodes of the joined body with the solid polymer electrolyte membrane interposed between the two gas diffusion electrodes and a hydrogen-containing gas is supplied to the gas diffusion electrode connected to the positive electrode, And the following reaction occurs on the negative electrode side. Positive electrode (+): H ₂ (low pressure) → 2H ⁺ + 2e ⁻ Negative electrode (−): 2H ⁺ + 2e ⁻ → H ₂ (high pressure)

Then, the pressure of hydrogen on the positive electrode side (P
The relationship between _H2 ) _I , the hydrogen pressure (P _H2 ) _II on the negative electrode side, and the voltage E is shown by the following Nernst equation of Formula 1 below.

[0010]

(Equation 1)

From the Nernst equation, it is found that increasing the voltage increases the hydrogen pressure (P _H2 ) _II on the negative electrode side,
For example, to increase the pressure ten times, the voltage should be increased to ten times In.

Further, in the hydrogen booster of the present invention, only hydrogen is extracted from the negative electrode side, and CO and CO ₂
Will be removed as a result. However, since CO reduces the catalytic activity of the gas diffusion electrode on the positive electrode side, it is preferable to remove CO by previously changing it to CO ₂ .

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

FIG. 1 conceptually shows a hydrogen booster according to one embodiment. As shown in FIG.
Is a solid polymer electrolyte membrane 101 and two gas diffusion electrodes 10
It has a joined body sandwiched between 2A and 102B. Here, the gas diffusion electrodes 102A and 102B are
03A and 103B and gas diffusion films 104A and 104B. The joined body is sandwiched between gas separators 105 and 106 serving as a positive electrode and a negative electrode, respectively, and a power supply 107 is connected to the gas separators 105 and 106. The gas separators 105 and 106 are provided with a hydrogen supply groove 105a (when a hydrogen-containing gas is not humidified, a water supply groove is also formed at the same time) and a hydrogen discharge groove 106a.

In this embodiment, the gas diffusion electrodes 102A, 102
B has an average particle diameter of platinum of 50 °, hydrophilic carbon black and hydrophobic carbon black having an average particle diameter of 450 °, and polytetrafluoroethylene having an average particle diameter of 0.3 μm.
Reaction films 103A and 103B in the ratio of 7: 7: 3: 3
And hydrophobic carbon black having an average particle diameter of 420 ° and polytetrafluoroethylene having an average particle diameter of 0.3 μm are:
Hydrophobic gas diffusion films 104A and 104B having a ratio of 3
It is composed of The reaction films 103A and 103B and the hydrophobic gas diffusion films 104A and 104B can be obtained by mixing a solvent such as solvent naphtha, alcohol, water, and hydrocarbon with each raw material powder other than platinum, and then forming the mixture by compression. These are stacked and rolled, and 0.56 mg / cm ² of Pt is supported on the reaction films 103A and 103B by a platinum chloride oxidation-reduction method, whereby gas diffusion electrodes 102A and 102B are manufactured. On the other hand, as the solid polymer electrolyte membrane 101, a 0.17 mm thick perfluorosulfonic acid polymer membrane (Nafion 117: manufactured by DuPont) was used. Then, the gas diffusion electrodes 102A,
The solid polymer electrolyte membrane 101 is sandwiched between the bases 102B and hot-pressed to form a joined body.
Sandwiched between two metallic gas separators 105, 106,
The power supply 107 is connected to form the hydrogen booster 100.

When the humidified H ₂ gas is supplied to the gas separator 105 using the above-described hydrogen pressurizing apparatus 100, the gas separator 105 receives 10 atm from the hydrogen discharge groove 106 a.
Of high-pressure hydrogen gas was obtained. The condition at this time is
It was 0.25 V at 1.00 A / cm ² .

FIG. 2 shows an example of a fuel cell system incorporating the above-described hydrogen pressurizing device 100. As shown in the figure, the methanol reformed gas supplied to the hydrogen electrode 12 of the fuel cell body 11 is produced by a methanol reformer 13. The methanol reformer 13 includes a reformer 14 and a preheater 1
5, the reforming section 14 is heated by the combustion of a combustion gas composed of unreacted gas and air from the hydrogen electrode 12, and the preheating section 15 is heated by the exhaust gas of the combustion gas heated the reforming section 14. It is supposed to be. This preheating section 1
5 is connected to a methanol tank 17 via a methanol supply pipe 16 for reforming. In the middle of the methanol supply pipe 16 for reforming, methanol 18 in the methanol tank 17 serving as a raw material of the reformed gas is converted into methanol. A pump 20 driven by a motor 19 for pumping to the quality device 13 is attached. In the middle of the reforming methanol supply pipe 16, one end is connected to the other end of a water supply pipe 22 that communicates with the water tank 21. A pump 25 driven by a motor 24 for pumping water 23 in a water tank 21 to be supplied into the methanol supply pipe 16 for reforming is attached.

Therefore, while passing through the preheating tube 26 in the preheating section 15, the reforming raw material comprising the methanol 18 and the water 23 is mixed with the high-temperature combustion exhaust gas generated by the combustion of the combustion gas. 200 ~ 500 ℃ by heat exchange in
Preheated to a degree. The preheated reforming raw material is gasified in the reforming section 14 and passes through the reformed gas generation pipe 27,
It comes into contact with the reforming catalyst filled in the reformed gas generation pipe 27 under heating, and is reformed by the next reforming reaction. CH ₃ OH + nH ₂ O → (1-n) CO + nCO ₂ + (2 + n) H ₂ where 0 <n <1 In such a reforming, the mixing ratio between methanol 18 and water 23 is 1 mole of methanol. Water to 0.05
It is desirable to set the molar amount to about 5 mol. Further, in order to efficiently perform the reforming reaction of the raw material gas, the pressure in the reformed gas generation pipe 27 is set to 0 per square centimeter.
It is preferable that the pressure is set to about 20 kg weight to 20 kg weight, and the temperature inside the reformed gas generation pipe 27 is set to about 200 ° C. to 600 ° C. As the reforming catalyst, for example, platinum (Pt), palladium (Pd) and rhodium (R
h) and one containing at least one element of nickel (Ni), or copper (Cu) and one containing at least one element of zinc (Zn) and chromium (Cr).

When the methanol reformer 13 is started, methanol 18 in a methanol tank 17 is supplied in place of unreacted gas from the battery body 11 used for combustion gas. That is, the starting methanol supply pipe 2 connecting the reformer 14 and the methanol tank 17
8 is provided, and the methanol supply pipe 28 for starting is provided.
A starting device 29 is provided in the middle of the process. The starting device 29 includes a starting fuel supply pump (not shown) for pumping methanol 18 in the methanol tank 17 to a nozzle unit (not shown) in the reforming unit 14, and methanol 18 supplied from the starting fuel supply pump. And a methanol vaporizer (not shown) for feeding the vaporized gas to a nozzle (not shown).

On the other hand, a first CO reduction device 30 is provided so as to communicate with the reformed gas outlet side of the methanol reformer 13. The first CO reduction device 30 is filled with a CO shift catalyst for reducing CO in the reformed gas generated by the reforming reaction in the reformed gas generation pipe 27. As the CO shift catalyst, for example, copper (C
u) and zinc (Zn) containing at least one element. Here, in the CO shift processing in the first CO reduction device 30, CO is converted into CO ₂ by a reaction with H ₂ O, and the CO concentration is reduced to about 1%.

The reformed gas supply pipe 31 communicating with the first CO reduction device 30 is connected to a second CO reduction device 32. In the second CO reduction device 32, a process (select oxo) for reducing CO from about 1% to about 100 ppm as described above by introducing air into the reformed gas is performed. .

In this embodiment, the reformed gas whose CO is reduced in this way is introduced into the hydrogen pressurizing device 100, and the hydrogen gas pressurized by the hydrogen pressurizing device 100 is humidified by the humidifying device 33. Thereafter, the fuel is introduced to the hydrogen electrode 12 side of the fuel cell main body 11. That is, the reformed gas supply pipe 3
A hydrogen booster 100 and a humidifier 32 are mounted between the first second CO reduction device 32 and the fuel cell main body 11. Of the reformed gas sent to the hydrogen electrode 12 of the fuel cell body 11 in this way, the surplus unreacted gas communicates between the fuel cell body 11 and the reforming section 14 of the methanol reformer 13. The gas is supplied to the reforming section 14 via the unreacted gas supply pipe 34.

On the other hand, a blower 37 is connected to an oxygen electrode 35 of the fuel cell main body 11 through an air supply pipe 36.
The pressurized air from the blower 37 is sent under pressure to the oxygen electrode 35 side. Then, this air is supplied to a steam-water separator 38 connected to the oxygen electrode 35 in a state of containing reaction product water on the oxygen electrode 35 side in the fuel cell main body 11, and water in the water is collected by a water recovery pipe. 39 through the water tank 21
And the gaseous component is discharged from the exhaust pipe 40 to the outside.

Here, the blower 37 is driven by a blower drive motor 42 supplied with electricity from a storage battery 41 as a power supply. The storage battery 41 has the first CO
The electricity generated by the generator 44 driven by the exhaust turbine 43 interposed in the reformed gas supply pipe 31 between the reduction device 30 and the second CO reduction device 32 is stored. . Further, a second air supply pipe 45 branched from the air supply pipe 36 from the blower 37 communicates with the middle of the methanol supply pipe 28, and the methanol is supplied through the second air supply pipe 45 as described above. Reformer 1
Air serving as combustion gas in the third reforming section 14 is supplied. The motors 19 and 24 are also operated by electricity supplied from the storage battery 41, similarly to the blower drive motor.

The water tank 21 and the fuel cell body 1
1 and the humidifier 33 are connected via a cooling water circulation pipe 46, and the water tank 21 and the fuel cell main body 11 are connected to each other.
In the middle of the cooling water circulation pipe 46 between
The water 23 is supplied to the fuel cell main body 11 to cool the fuel cell main body 11, and the heated cooling water is supplied to the humidifier 3.
There is provided a pump 48 driven by a motor 47 for feeding to the pump 3. In the humidifier 33, the reformed gas supply pipe 31
The reformed gas flowing inside and the heated cooling water are in contact with each other via the gas diffusion film, so that steam is added to the reformed gas at a steam partial pressure corresponding to the temperature of the heated cooling water. Has become. Further, the motor 47 is driven by electricity of a storage battery.

When power is generated by such a fuel cell, CO in the hydrogen source reformed gas is removed by the hydrogen booster 100, and high-pressure hydrogen gas is removed from the hydrogen electrode 12 of the fuel cell body 11.
As a result, the state where the power density was improved was maintained.

[0027]

As described above, according to the hydrogen booster of the present invention, high-pressure hydrogen gas can be easily obtained, and when this gas is applied to a fuel cell, the C of the catalyst on the hydrogen electrode side can be obtained.
The effect of preventing a decrease in activity due to O poisoning and connecting good power generation with improved current density is achieved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a hydrogen booster according to one embodiment.

FIG. 2 is a schematic diagram showing a fuel cell system according to one embodiment.

FIG. 3 is an explanatory diagram showing an example of a fuel cell main body.

[Explanation of symbols]

 Reference Signs List 1 reformed gas supply pipe 2A, 2B adsorbent packed tower 6A, 6B air introduction pipe 8A, 8B exhaust pipe 11 fuel cell body 12 hydrogen electrode 13 methanol reformer 14 reforming section 15 preheating section 16 reforming methanol supply pipe 17 Methanol tank 18 Methanol 21 Water tank 23 Water 30 First CO reduction device 31 Reformed gas supply tube 32 Second CO reduction device 33 Humidifier 35 Oxygen electrode 36 Air supply tube 100 Hydrogen booster 101 Solid polymer electrolyte membrane 102A, 102B Gas diffusion electrode 103A, 103B Reaction film 104A, 104B 105, 106 Gas separator 107 Power supply

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tokuichi Mineo 3000 Tana, Sagamihara-shi, Kanagawa Mitsubishi Heavy Industries, Ltd. Sagamihara Works (56) References JP-A-62-7886 (JP, A) JP-A-2 -311302 (JP, A) JP-A-61-114478 (JP, A) JP-B-58-15544 (JP, B1) (58) Fields studied (Int. Cl. ⁷ , DB name) H01M 8/00- 8/106 B01D 53/00

Claims (2)

(57) [Claims] A carbon monoxide reducing means for reducing carbon monoxide from methanol reformed gas, a joined body formed by sandwiching a solid polymer electrolyte membrane between two gas diffusion electrodes, A power supply for applying a voltage to the two gas diffusion electrodes,
A hydrogen supply system for supplying a hydrogen-containing gas to the gas diffusion electrode connected to the positive electrode of the power supply, and hydrogen for extracting a high-pressure hydrogen gas of 10 atm or less from the gas diffusion electrode connected to the negative electrode of the power supply A hydrogen booster comprising: a discharge system; 2. A fuel cell for generating power by supplying hydrogen gas and oxygen or air to hydrogen electrodes and oxygen electrodes on both sides of a joined body formed by joining a solid polymer electrolyte membrane between two gas diffusion electrodes. Wherein the hydrogen gas supply line to the hydrogen electrode is provided with the hydrogen pressure increasing device according to claim 1, and the high pressure hydrogen gas of 10 atm or less from the hydrogen discharge line of the hydrogen pressure increasing device is supplied to the hydrogen gas supply line. A fuel cell characterized in that it is supplied to the poles.