JPS61218073A - Fuel cell system - Google Patents

Abstract

PURPOSE:To reutilize recovered H2 gas as raw material for power generation of fuel cell or heating starting fuel of reformer by arranging a hydrogen gas recovering unit and a receiver tank in which hydrogen gas is stored in a gas recovering line of fuel cell. CONSTITUTION:A PSA type hydrogen gas recovering unit 20, a compressor 21, and a receiver tank 22 are arranged in order in a gas recovering line 9. A branch recovered hydrogen circulation line 24 and a control valve 28 are set in an inlet side hydrogen supply line 7 of a fuel cell 8, and the control valve 28 is controlled by pressure of the receiver tank 22. The recovered H2 gas stored in the receiver tank 22 is usually used as power generating fuel gas of the fuel cell 8 through the recovered hydrogen circulation line 24. When a reformer 1 starts, H2 gas is introduced into a fuel hydrogen recovering line 25 and supplied to a fuel catalyst layer 15 of the reformer 1.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a fuel cell device, and particularly to the same device suitable for reusing hydrogen contained in battery exhaust gas.

(Prior Art) In conventional fuel cells of this type, particularly in phosphoric acid fuel cell devices, as shown in FIG. are used. That is, the reformer 1 has a structure in which a reaction tube 13 filled with a reforming catalyst 14 is provided on the inside and a combustion catalyst layer 15 is provided on the outside.By burning the fuel 4 in the combustion catalyst layer 15, , the reaction tube 13 is heated. The reaction tube 13 heated in this way
When raw material gases, such as natural gas (mainly methane) and steam, are supplied through supply lines 2 and 3, respectively, a reformed gas 5 consisting of a mixed gas of H2 and co is produced. This reformed gas 5 is then passed through a shift converter 6, where the CO gas it contains is converted to H2 gas, and the resulting H2 rich gas is supplied to the fuel cell 8 via the hydrogen supply line 7. A portion of the H2 gas thus supplied is consumed for power generation, but the remainder is exhausted outside the fuel cell 8 and becomes off-gas. Usually, the H2 concentration of the hydrogen-rich gas is about 80%, while that of the off-gas is about 30%. Since such off-gas still has sufficient flammability, it has conventionally been sent to the reformer 1 via the hydrogen recovery line 9 and reused as the fuel 4. However, no attempt has been made to use it as a raw material for power generation in the fuel cell 8.

Furthermore, in the conventional heating of the reaction tube 13, the catalytic combustion method described above has been adopted, but this method allows the combustion space to be significantly smaller than other burner methods, and the combustion reactivity is extremely low. This is because complete combustion is possible regardless of the air-fuel ratio or fuel calorific value, and pollution-free combustion is possible with low noise and low NOx. However, when using this combustion method, it is necessary to maintain a constant temperature level depending on the fuel when ignition combustion starts on the catalyst surface, and therefore it is necessary to provide a startup burner or a hot air stove for startup. The disadvantage is that the device becomes unavoidably complicated.

(Problems to be Solved by the Invention) An object of the present invention is to eliminate the drawbacks of the prior art described above and provide a fuel cell device that can utilize hydrogen in off-gas discharged from a fuel cell as a raw material for power generation in the fuel cell. It's about doing.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a reformer that performs a reforming reaction under heating using a catalytic combustion method as a hydrogen gas supply source for a fuel cell, and a hydrogen gas supply source for a fuel cell. In a fuel cell device equipped with a line for recovering used hydrogen-containing off-gas as fuel for catalytic combustion, the off-gas recovery line is provided with a hydrogen gas separation and recovery device and a receiver tank for storing the recovered hydrogen gas under increased pressure. a recovered hydrogen circulation line that branches from the downstream side of the receiver tank and is connected to the hydrogen supply line on the inlet side of the fuel cell; It is characterized by providing a control means for releasing excess recovered hydrogen into the line.

Any known hydrogen gas separation and recovery device can be applied to the above-mentioned hydrogen gas separation and recovery device.
A pressure swing (PSA) method that utilizes a film adhesion phenomenon is preferred.

In the present invention, the activation of the combustion catalyst layer is achieved by providing a heating device in the fuel hydrogen recovery line on the downstream side of the receiver tank that can raise the temperature of hydrogen to the auto-ignition temperature under contact with the combustion catalyst. It can be easily done.

In addition, a flow rate controller is installed in the hydrogen supply line to which the recovered hydrogen circulation line is connected, and the flow rate is adjusted to a predetermined value.
By controlling the control valve provided in the supply line of raw material gas for the reformer, the amount of raw material gas can be adjusted according to the circulating amount of recovered hydrogen, and the amount of raw material gas can be reduced.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples shown in the drawings.

FIG. 1 is a system diagram of a fuel cell device according to an embodiment of the present invention. This device has the same configuration as shown in FIG. 3, consisting of a reformer 1, a shift converter 6, and a fuel cell 8.
The off-gas recovery line 9 is equipped with the PSA type hydrogen gas separation and recovery device 20, a compressor 21, and a receiver tank 2.
2 are provided in sequence, and a recovered hydrogen circulation line 24 branched from the downstream side of the receiver tank 22 to the hydrogen supply line 7 on the inlet side of the fuel cell 8 and a control valve 28 are provided, and the control valve 28 can be controlled by the pressure of the receiver tank 22. The difference is that it is done like this. In addition, in the figure, 23 is an electric heater installed in the hydrogen recovery line 25 for fuel on the downstream side of the receiver tank 22, and raises the temperature of hydrogen to the spontaneous ignition temperature in contact with the combustion catalyst layer 15, and 26 is a hydrogen supply The flow rate of the line 7 is measured, and the supply line 2 of the raw material gas for the reformer is adjusted so that the flow rate is constant.
29 is a pressure regulator that adjusts the control valve 28 of the recovered hydrogen circulation line 24 so that the pressure in the receiver tank 22 is maintained at a constant value.

In an apparatus having such a configuration, off-gas containing approximately 30% residual H2 is discharged from the fuel cell 8, and this gas is first sent to the hydrogen gas separation and recovery device 20 via the off-gas recovery line 9. Here, H2 gas is recovered, and this gas is then pressurized by a compressor 21 and then stored in a receiver tank 22. The stored H2 gas is extracted in a timely manner and reused as raw material gas for battery power generation or heating fuel for the reformer 1. First, during steady operation,
Pulp 3 generally installed in hydrogen recovery line 25 for fuel
0 is closed, and the pressure regulator 29 of the receiver tank 22 is closed.
Under the operation of the control valve 28, the pressure inside the receiver tank 22 is drawn out so as to be constant. Normally, the receiver tank 22 is in a full state, and when the pressure exceeds this, the control valve 28 is activated. The recovered hydrogen is then released from the recovered hydrogen circulation line 24. In this case, the amount of H2 gas extracted will vary, but by changing the amount of H2 gas supplied from the reformer 1 accordingly,
raw materials can be saved.

Such control of the H2 gas supply amount is performed using the hydrogen supply line 7.
This is done by adjusting the flow rate of the raw material gas (methane) sent from the supply line 2 to the reformer 1 based on a series of control systems consisting of a flow rate controller 26 and a raw material (methane) regulating valve 27.

On the other hand, when starting up the reformer 1, the pulp 30 is opened to guide H2 gas to the fuel hydrogen recovery line 25, and the electric heater 23 heats it to the contact ignition temperature. It is supplied to the combustion catalyst layer 15. In this case, the contact ignition temperature of H2 gas is shown in Figure 2 (Pd
As is clear from the comparison diagram of the ignition temperature of various fuels in the presence of a system combustion catalyst, it is extremely low at most 50°C, so the heating temperature by the electric heater 23 can be as low as 50-100°C. When the heated H2 gas is introduced into the combustion catalyst layer 15, it immediately ignites and reaches a sufficient temperature, making it easy to switch to the normal fuel gas 4. Note that the H2 gas consumed at the time of startup is replenished by the hydrogen gas separation collector 20 during steady operation.

If a Molecule Sieve type is adopted as the hydrogen gas separation and recovery device 20, it will be a two-unit switching type, which will generate pulsation, but the receiver tank 22 also has the role of a pulsation tank to calm this down. .

(Effects of the Invention) According to the present invention, H
A two-gas separation/recovery device and a receiver tank that stores the recovered H2 gas under increased pressure are installed, and the recovered H2 gas stored in the receiver tank is used as the raw material gas for power generation of the fuel cell during steady operation, and as a reformer during startup. This makes it possible to reuse the fuel as a fuel for starting heating, thereby achieving effects such as reduction in H2 gas generated by the reformer, reduction in operating costs, and simplification of startup equipment.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a fuel cell device according to an embodiment of the present invention, Fig. 2 is a diagram showing a comparison of contact ignition temperatures of various fuels, and Fig. 3 is a system diagram of a conventional fuel cell device. It is. 1... Reformer, 2... Raw material gas supply line, 3...
- Steam supply line, 4... Fuel, 5... Reformed gas, 6... Shift converter, 7... Hydrogen supply line, 8... Fuel cell, 9... Hydrogen recovery line, 13
...Reaction tube, 14--Reforming catalyst, 15--Combustion catalyst layer, 20--Hydrogen gas separation and recovery device, 21--Compressor, 22--Receiver tank, 23--Electric heat Heater, 24...Recovered water im ring line, 25...Hydrogen recovery line for fuel, 26...Flow rate controller, 27.2
8... Control valve, 29... Pressure regulator, 30... Pulp. Agent Patent Attorney Takenaga Kawakita Figure 1 Figure 3

Claims (2)

[Claims] (1) Equipped with a reformer that performs a reforming reaction under heating using a catalytic combustion method as a hydrogen gas supply source for fuel cells, and a line that recovers hydrogen-containing off-gas after use in the battery as fuel for catalytic combustion. In the above-mentioned off-gas recovery line, the above-mentioned off-gas recovery line includes a hydrogen gas separation and recovery device, a receiver tank that stores the recovered hydrogen gas under increased pressure, and after branching from the downstream side of the receiver tank, the hydrogen gas is connected to the inlet side of the fuel cell. A recovered hydrogen circulation line connected to a supply line, and a control means for releasing excess recovered hydrogen to the recovered hydrogen circulation line when the pressure in the receiver tank exceeds a predetermined value. fuel cell device. (2) Claim 1 provides that a flow rate controller is provided in the hydrogen supply line, and means is provided for adjusting the amount of raw material supplied to the reformer so that the hydrogen flow rate becomes a predetermined value. Characteristic fuel cell device.