JP2001167784A - Fuel cell system - Google Patents

Abstract

(57) [Problem] To provide a fuel cell system with improved reforming responsiveness of a hydrocarbon fuel. SOLUTION: The fuel cell system includes a reformer 3 for reforming a hydrocarbon-based fuel to generate a fuel gas containing hydrogen.
And a fuel cell 4 that receives supply of the generated fuel gas and obtains an electromotive force by an electrochemical reaction of the fuel gas. Here, the reformer 3 has a plasma discharge device 32, in which a hydrocarbon-based fuel is introduced via a steam addition device 31, and this is turned into plasma and reformed. The fuel gas containing hydrogen generated by the reforming is supplied to the fuel cell 4 together with oxygen separately introduced.

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 for generating electric energy by supplying a fuel cell containing hydrogen obtained by reforming a hydrocarbon fuel to a fuel cell.

[0002]

2. Description of the Related Art As a power source for automobiles, an internal combustion engine has been the mainstream, but in recent years, a fuel cell system has been attracting attention because of its excellent energy conversion efficiency. This fuel cell system includes a fuel cell, and obtains an electromotive force by an electrochemical reaction using hydrogen and oxygen as an oxidizing agent. As the hydrogen used for the fuel cell, a method in which hydrogen generated in advance outside the vehicle is stored in the vehicle, and if necessary, taken out and used can be considered. However, when hydrogen is stored in a vehicle, it is actually inconvenient to handle it because it needs to be pressurized at a high pressure or kept at a very low temperature. Therefore, as a practical method, a hydrocarbon-based fuel such as methanol, which is easy to handle, is reformed on a vehicle to generate a fuel gas containing hydrogen,
A promising method is to supply this to a fuel cell.

[0003] As a method of reforming hydrocarbon fuels,
A steam reforming method or a partial oxidation method using a catalyst has been developed. Among them, the steam reforming method is, for example, as described in JP-A-8-185877, in which a reforming reaction between methanol and water is carried out through a reforming catalyst in a range of 250 to 3 times.
The process is carried out at a temperature of 00 ° C., whereby steam reforming of methanol is performed to generate hydrogen gas.

[0004]

However, in the conventional method using a catalyst for reforming, the responsiveness of fuel reforming in the early stage of system operation is poor, and it takes five to five hours before sufficient hydrogen can be supplied to the fuel cell. There was a problem that a warm-up of about 10 minutes was required.

Accordingly, it is an object of the present invention to provide a fuel cell system having improved responsiveness of reforming a hydrocarbon fuel.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a reformer for reforming a hydrocarbon-based fuel to generate a fuel gas containing hydrogen, and to supply the generated fuel gas and to generate an electric power of the fuel gas. A fuel cell system comprising: a fuel cell that obtains an electromotive force by a chemical reaction, wherein the fuel cell system includes a plasma discharge device in which the reformer converts the hydrocarbon-based fuel into plasma. . Here, as the hydrocarbon-based fuel, for example, methanol, gasoline, natural gas, or the like is used.

[0007] When carbon monoxide is contained in the fuel gas discharged from the plasma discharge device, it is desirable to dispose, for example, a steam addition device or a hydrogen separation membrane downstream thereof in order to remove the carbon monoxide. . Further, in order to further increase the degree of fuel reforming, the above-mentioned conventional reforming catalyst may be provided upstream or downstream of the plasma discharge device.

As described above, according to the present invention, since a hydrocarbon-based fuel such as methanol is converted into plasma by the plasma discharge device to generate a fuel gas containing hydrogen, the fuel gas is supplied to the plasma discharge device. By controlling the electric power, the amount of hydrogen supplied to the fuel cell can be controlled with good responsiveness, and the startability and responsiveness of the system can be improved.

[0009]

FIG. 1 is a block diagram showing one embodiment of a fuel cell system according to the present invention. As shown in the figure, the present system includes a methanol tank 1, a steam generator 2, a reformer 3, and a fuel cell 4. Reformer 3
Are the first steam addition device 31 and the plasma discharge device 3
2 and a second steam addition device 33, which is provided with methanol from a methanol tank 1 and a steam generation unit 2
And reforming the steam to generate a fuel gas containing hydrogen and supplying the fuel gas to the fuel cell 4. Further, oxygen is separately supplied to the fuel cell 4. This oxygen is
For example, it is obtained by introducing air from the atmosphere.

A high voltage is applied to the plasma discharge device 32 from the high voltage generator 5. The voltage generated by the high voltage generator 5 is controlled by an electronic control unit (ECU) 6.
The ECU 6 detects the operating state of the fuel cell 4 and supplies hydrogen according to the amount of power generation required there.
The amount of fuel or the amount of water vapor introduced into the first steam addition device 31 is controlled, and the power supplied from the high voltage generator 5 to the plasma discharge device 32 is controlled.
Adjustment of fuel reforming in the plasma discharge device 32 is performed.
Next, a fuel reforming method using plasma will be described.

FIG. 2A is a diagram for explaining the principle of fuel reforming in the plasma discharge device 32. As illustrated, the plasma discharge device 32 has a positive (+) electrode 34 and a negative (−) electrode 35, and is configured so that a high voltage is applied from the high voltage generator 5. Now, assuming that methanol (CH ₃ OH) and water vapor (H ₂ O) are introduced, they are turned into plasma in a plasma discharge device 32 to which a high voltage is applied, and then recombined to produce hydrogen (H ₂ ). And carbon dioxide (CO ₂ ). In the present invention, by controlling the power supplied from the high-voltage generator 5 to the plasma discharge device 32, the amount of hydrogen supplied to the fuel cell can be adjusted with good responsiveness.

FIG. 2B is a diagram for explaining the operation of the second steam addition device 33 disposed downstream of the plasma discharge device 32. In the plasma discharge device 32, not only hydrogen and carbon dioxide but also carbon monoxide may be generated during fuel reforming. Since carbon monoxide is toxic to the fuel cell, in such a case, it is preferable to provide a second steam addition device 33 as shown. The second steam addition device 33 uses a CO shift conversion reaction or a selective oxidation reaction by adding steam (H ₂ O) to the generated carbon monoxide (CO) to convert them into carbon dioxide (CO). ₂ ) and hydrogen (H ₂ ). When carbon monoxide is not generated in the plasma discharge device 32, there is no need to provide the second steam addition device 33.

FIGS. 3A and 3B are block diagrams showing other examples of the reformer according to the present invention. The reformer shown in FIG. 3A is provided with a hydrogen separation membrane (Pd membrane) 36 downstream of the plasma discharge device 32. As described above, the CO generated by the plasma discharge device 32 can be removed using a CO shift conversion reaction or a selective oxidation reaction. It is desirable to use a hydrogen separation membrane 36 as in the example. The hydrogen separation membrane 36 can quickly separate only hydrogen from the reformed gas. In this case, the membrane permeation pressure of the hydrogen separation membrane 36 is preferably 9 kg /
cm ² .

The reformer shown in FIG. 3B is provided with a reforming catalyst 37 described above as a conventional technique downstream of the plasma discharge device 32. In this example, the plasma discharge device 32 and the conventional reforming catalyst 37 are used in combination, whereby the degree of fuel reforming can be further increased. In this case, the reforming catalyst 37 can be provided upstream of the plasma discharge device 32. Also in this example, although not shown, the above-described second method is used to remove CO.
May be provided at the lowermost stream.

As described above, in the present invention, it is possible to quickly reform the fuel by using the plasma, so that the response delay of the hydrogen supply at the start of the system operation or at the time of load fluctuation can be greatly improved. it can. Also,
In the present invention, the amount of generated hydrogen can be increased or decreased according to the supply power (plasma consumption energy) applied to the plasma discharge device. In other words, it is possible to control the plasma discharge device so as to have the minimum required plasma consumption energy in order to obtain the required amount of generated hydrogen, and it is possible to suppress fuel consumption deterioration.

[0016]

According to the present invention, it is possible to obtain a fuel cell system having improved responsiveness of reforming hydrocarbon fuel.

[Brief description of the drawings]

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

2A is a diagram for explaining the principle of fuel reforming in a plasma discharge device, and FIG. 2B is a diagram for explaining the operation of a second steam addition device disposed downstream of the plasma discharge device. FIG.

FIGS. 3A and 3B are block diagrams showing other examples of the reformer according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Methanol tank 2 Steam generation part 3 Reformer 4 Fuel cell 5 High voltage generator 6 Electronic control unit (ECU) 31, 33 Steam addition device 32 Plasma discharge device 34, 35 Electrode 36 Hydrogen separation membrane 37 Reforming catalyst

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akio Shiratori 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation F-term (reference) 4G040 EA02 EA03 EA06 EB11 5H027 AA02 BA01

Claims (1)

[Claims] 1. A reformer for reforming a hydrocarbon-based fuel to produce a fuel gas containing hydrogen, and a fuel which receives the produced fuel gas and obtains an electromotive force by an electrochemical reaction of the fuel gas. A fuel cell system comprising: a battery; and the reformer includes a plasma discharge device that converts the hydrocarbon-based fuel into plasma.