JP2002270208A - Fuel changing method and fuel changing device for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel changing method and a fuel changing device for suppressing to the minimum the output fluctuation of the fuel cell, even if the fuel is changed. SOLUTION: The fuel changing device of a fuel cell, which generates electricity using as a fuel the spare fuel and the reformed fuel reformed from the main fuel through a reformer 7, comprises a spare fuel control valve 5 that is installed at the fuel supply passage 4 for supplying the spare fuel to the fuel cell 1, a main fuel control valve 8 that is installed at the supply passage 6 for supplying the reformed fuel reformed from the main fuel through a reformer 7 to the fuel cell 1, and a fuzzy control part 9 that controls the spare fuel control valve at the start of running, so as to supply the spare fuel to the fuel cell, and controls the spare fuel control valve and the main fuel control valve when the temperature of the reformer has risen and reached the normal state, so as to change gradually from the spare fuel to the reformed fuel, and to reduce the fluctuation of output of the fuel cell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel switching method and a fuel switching device for a fuel cell which switches between a reserve fuel and a reformed fuel obtained by reforming a main fuel via a reformer and supplies the fuel to the fuel cell. . For example, pure hydrogen reserve fuel and LP
The present invention relates to a fuel switching method and a fuel switching device for a fuel cell that switches between a gas or a hydrocarbon-based main fuel such as gasoline and supplies the fuel to the fuel cell.

[0002]

2. Description of the Related Art Conventionally, as a fuel supply system for a fuel cell, a system using only pure hydrogen or a spare fuel of pure hydrogen and a hydrocarbon-based main fuel such as LP gas or gasoline are used, and these are switched. A system for supplying the fuel cell is known. For example, JP-A-51-4716 discloses a fuel cell electric vehicle. This involves supplying hydrogen generated by heating a metal hydride to a fuel cell, and providing a hydrogen storage tank for storing hydrogen in a gaseous state. When the load on an automobile increases, the hydrogen stored in the hydrogen storage tank is used. The configuration is such that it is additionally supplied to the fuel cell.

[0003] Japanese Patent Application Laid-Open No. 4-119773 discloses a reformer and a proton conductive fuel cell. This is a configuration in which a hydrogen separator is provided in a reforming reaction tube in a reforming vessel to perform fuel reforming from a fuel such as methane and supply pure hydrogen to a fuel cell.

[0004] Also, Japanese Patent Application Laid-Open No. 5-47401 discloses that
A fuel switching method and device for a fuel cell is disclosed. This is because the sensor detects an abnormality in the supply amount of the main fuel,
The control device changes the spare fuel supply amount to an optimal value stored in advance in accordance with the decrease in the fuel cell output and the main fuel supply amount. In addition, the control device changes the supply amount of steam for reforming the main fuel and the spare fuel and the temperature of the reformer to optimal values stored in advance according to the supply amounts of the main fuel and the reserve fuel. . Thereby, the supply amount of the reforming steam,
Due to differences in reforming conditions such as fuel supply amount and reforming reaction heat,
This configuration suppresses a transient decrease in fuel cell output caused by a temporary decrease in the amount of hydrogen in the reformed gas during fuel switching.

[0005]

Among the above-mentioned prior arts, the technology disclosed in Japanese Patent Application Laid-Open No. 51-4716 is a system using only pure hydrogen as fuel for a fuel cell, and the fuel cost is high. . For this reason, in a fuel cell for an automobile, hydrocarbons such as LP gas are required for a cell reaction in a reformer as disclosed in JP-A-4-121973 or JP-A-5-47401. Many systems are reformed as a hydrogen-rich gas and supplied to a fuel cell.

However, the method using only reformed hydrogen as fuel requires a certain period of time until the reformer enters a steady state, during which time the fuel cell cannot generate power. Therefore, it is inconvenient when quick power generation is required as in the case of a fuel cell for an automobile. For this reason, until the reformer reaches a steady state, power is generated using a spare fuel made of pure hydrogen, When the fuel cell reaches a steady state, a fuel switching method of switching to reformed hydrogen to generate power can be considered.

However, when switching from the pure hydrogen reserve fuel to the reformed hydrogen as described above, since the purity of the pure hydrogen and the reformed hydrogen (the reformed hydrogen is 70 to 80%) is different, the conversion from the spare fuel to the main fuel is performed. Switching to high quality hydrogen at once can cause a problem that the output of the fuel cell fluctuates sharply (output drop), and in particular, the driving mode of an automobile fluctuates, which is dangerous.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and it is an object of the present invention to provide a fuel cell capable of minimizing the output fluctuation of the fuel cell even at the time of fuel switching. It is to provide a fuel switching method and a fuel switching device.

[0009]

SUMMARY OF THE INVENTION A fuel switching method for a fuel cell according to the present invention is a fuel switching method for a fuel cell which generates electricity using a spare fuel and a reformed fuel obtained by reforming a main fuel through a reformer. In the method, the reserve fuel is supplied to the fuel cell at the start of operation, and then, when the reserve fuel is gradually switched from the reserve fuel to the reformed fuel, the output of the fuel cell is changed by fuzzy control. It is characterized in that it is controlled to be small. According to such a fuel switching method, at the start of operation, the reserve fuel is supplied to the fuel cell, so that it is possible to cope with quick power generation. Thereafter, the fuel is gradually switched from the reserve fuel to the reformed fuel. At this time, the fuzzy control moderately suppresses the fluctuation of the output of the fuel cell, so that an economical and stable operation can be realized. Here, the timing for gradually switching from the reserve fuel to the reformed fuel is preferably, for example, switched when the temperature of the reformer rises and reaches a steady state.

The fuel cell switching device for a fuel cell according to the present invention is a fuel cell switching device for a fuel cell that generates electricity using a spare fuel and a reformed fuel obtained by reforming a main fuel through a reformer.
A reserve fuel control valve provided in a supply path for supplying the reserve fuel to the fuel cell; and a reserve fuel control valve provided in a supply path for supplying reformed fuel obtained by reforming the main fuel via a reformer to the fuel cell. Main fuel control valve, at the start of operation, controls the spare fuel control valve so that the spare fuel is supplied to the fuel cell, when the temperature of the reformer rises and reaches a steady state, A fuzzy control unit that controls the spare fuel control valve and the main fuel control valve so that the fuel is gradually switched from the spare fuel to the reformed fuel, and that the fluctuation of the output of the fuel cell is reduced. It is characterized by. According to such a fuel switching device, at the start of operation, the spare fuel control valve is controlled so that the spare fuel is supplied to the fuel cell, so that quick power generation can be handled. Further, when the temperature of the reformer rises and reaches a steady state, the spare fuel control valve and the spare fuel control valve are controlled so that the fuel is gradually switched from the spare fuel to the reformed fuel, and that the fluctuation of the output of the fuel cell is reduced. Since the main fuel control valve is controlled, economical and stable operation can be realized.

In the above-described fuel cell switching method and apparatus, it is preferable that the spare fuel be pure hydrogen and the main fuel be a hydrocarbon fuel. If you do this,
Quick power generation with spare fuel and steady power generation with inexpensive main fuel. When gradually switching from the reserve fuel to the reformed fuel, it is desirable to gradually switch from the reserve fuel to the reformed fuel while monitoring the output of the fuel cell. It is desirable that the fuzzy control unit controls the reserve fuel control valve and the main fuel control valve so that the fuel is gradually switched from the reserve fuel to the reformed fuel, and the fluctuation of the output of the fuel cell is reduced.

In the above, the fuzzy control is
Considering the purity difference between the spare fuel and the reformed fuel, the fluctuation of the load connected to the fuel cell, etc., in the process of switching from the spare fuel to the reformed fuel, use a spare fuel that reduces the output fluctuation of the fuel cell. With the passage of time since the temperature of the reformer rises and reaches a steady state,
A fuzzy control rule may be determined in advance based on an experiment or the like based on the created model, and control may be performed according to the fuzzy control rule.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a fuel switching device for a fuel cell according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a fuel switching device for a fuel cell according to the present invention. The fuel switching device according to the present embodiment includes a fuel cell 1, a spare fuel tank 2 for storing a spare fuel made of pure hydrogen, a main fuel tank 3 for storing a hydrocarbon-based main fuel such as LP gas and gasoline, A reserve fuel control valve 5 provided in a supply path 4 for supplying reserve fuel of the reserve fuel tank 2 to the fuel cell 1;
A reformer 7 provided in a supply path 6 for supplying the main fuel to the fuel cell 1 and a main fuel control valve 8 provided in the supply path 6 connecting the reformer 7 and the fuel cell 1 And a fuzzy controller 9 that monitors the output of the fuel cell 1 and the reformer 7 and controls the spare fuel control valve 5 and the main fuel control valve 8.

As the fuel cell 1, for example, a polymer electrolyte fuel cell (PEFC) is used. This fuel cell (PEFC) has a structure in which a positive electrode and a negative electrode are arranged opposite to each other in a main body container, and a polymer electrolyte membrane is housed between them. Hydrogen is introduced into the positive electrode side, and air (oxygen) is introduced into the negative electrode side. Thus, a DC power is generated between the positive electrode and the negative electrode. In the present embodiment, a spare fuel (pure hydrogen) in the spare fuel tank 2 and a reformed hydrogen gas obtained by reforming the main fuel in the main fuel tank 3 through the reformer 7 are supplied to the positive electrode side of the fuel cell 1. It is supposed to be.

The reformer 7 is for reforming the main fuel to hydrogen, and has a catalyst for reforming the main fuel to hydrogen in a container. The main fuel may be reformed using an existing direction such as a steam reforming method, a partial oxidation method, and an autothermal method. In order to quickly switch from the reserve fuel to the reformed fuel, it is preferable to provide a heating means around the reformer 7. As the heating means, there are a combustion exhaust gas, a heater, and the like. As shown in FIG. 2, a reforming catalyst 13 is housed in an inner cylinder 11 in an inner / outer double cylinder structure. The structure may be provided with a heat insulating agent 14 supporting an oxidation catalyst therebetween. Pt (platinum), Mo
A noble metal-based oxidation catalyst such as (molybdenum) or V (vanadium) is supported, and at the start of operation, by supplying air and a part of the main fuel, heat is generated by an oxidation reaction, and the reforming catalyst 13 Heated. Thereby, the temperature of the reformer 7 can be raised to the predetermined temperature in a shorter time than when only the heater is used. Thereafter (after the temperature rise), the main fuel is switched to the reforming catalyst 13 side, whereby the reforming reaction is performed,
Hydrogen is produced. In addition, the oxidation catalyst supporting heat insulating material 14 is
Since it has a heat insulating effect, there is an advantage that heat loss is small.

The fuzzy control unit 9 considers the purity difference between the reserve fuel and the reformed fuel, changes in the load connected to the fuel cell 1 and the like, and in the process of gradually switching from the reserve fuel to the reformed fuel, From the relationship between the battery output and the change in hydrogen purity, the ratio between the reserve fuel and the reformed fuel that reduces the output fluctuation of the fuel cell 1 is determined after the temperature of the reformer 7 rises and reaches a steady state. As time elapses, it is created in advance through experiments, etc., and a fuzzy control rule is determined based on the created model, and according to the fuzzy control rule,
The auxiliary fuel control valve 5 and the main fuel control valve 8 are controlled.

More specifically, the control is performed based on the fuzzy control rules shown in FIG. In FIG. 3, (1) if the output of the fuel cell is higher than the target value and the purity of the supplied hydrogen is increased, the supply flow rate of pure hydrogen as the spare fuel is reduced,
(2) If the fuel cell output is higher than the target value and the supply hydrogen purity does not change, the supply flow rate of pure hydrogen as a reserve fuel is slightly reduced. (3) The fuel cell output is higher than the target value and the supply If the hydrogen purity is lowered, fuzzy control is performed so as to maintain the supply flow rate of pure hydrogen as a reserve fuel.

(4) If the fuel cell output is at the target value and the purity of the supplied hydrogen is increased, the supply flow rate of the pure hydrogen as the reserve fuel is slightly reduced. (5) The fuel cell output is at the target value and If the purity of the supplied hydrogen does not change, the supply flow rate of the pure hydrogen as the reserve fuel is maintained. (6) If the output of the fuel cell is at the target value and the purity of the supplied hydrogen is reduced, the pure hydrogen as the reserve fuel is Fuzzy control is performed so as to slightly increase the supply flow rate.

(7) If the output of the fuel cell is lower than the target value and the purity of the supplied hydrogen is increased, the supply flow rate of the pure hydrogen as the reserve fuel is maintained, and (8) the output of the fuel cell is lower than the target value. If the purity of the supplied hydrogen does not change, the supply flow rate of pure hydrogen as a reserve fuel is slightly increased. (9) If the output of the fuel cell is lower than the target value and the purity of the supplied hydrogen is decreased, the reserve fuel is used. Fuzzy control is performed to increase the supply flow rate of certain pure hydrogen.

Next, the operation of the fuel switching device for the fuel cell 1 will be described. At the start of operation, the reserve fuel control valve 5 is opened to supply pure hydrogen from the reserve fuel tank 2 to the fuel cell 1,
At the same time as the start of power generation, the reformer 7 is heated. When the reformer 7 warms up and reaches a steady state, the fuzzy controller 9 detects this and switches to the main fuel side as follows.

In general, the purity of the hydrogen reformed in the reformer 7 varies depending on the operation mode of the reformer 7 and the raw material (here, LP gas or gasoline).
80%. Therefore, pure hydrogen (almost 100% pure)
%), The output of the fuel cell 1 fluctuates (output decrease) when switching from the reserve fuel to reformed hydrogen at once. In particular, in a fuel cell for an automobile, there is a possibility that a safety problem may occur because the operation mode fluctuates. Therefore, in the present embodiment, when switching the fuel, the fuzzy control unit 9 controls the output of the fuel cell 1 so that the output fluctuates slowly.

That is, the output of the fuel cell 1 is monitored by the fuzzy control unit 9 and a change in the output is caught to appropriately control the ratio between the reserve fuel and the reformed fuel. In particular,
When the temperature of the reformer 7 rises and reaches a steady state, the fuzzy control unit 9 performs control in accordance with the fuzzy control rule shown in FIG. 3 and gradually changes the supply ratio between the reserve fuel and the reformed fuel. . As a result, the fuel is gradually switched from the reserve fuel to the reformed fuel, and a rapid output fluctuation of the fuel cell 1 can be prevented.

Since the ratio between the reserve fuel and the reformed fuel corresponding to the output of the fuel cell 1 differs depending on the purity of the reserve fuel, temperature conditions, and other conditions, the output of the fuel cell 1 is constantly monitored by the fuzzy control unit 9. By controlling the reserve fuel control valve 5 and the main fuel control valve 8 based on the output, the output fluctuation of the fuel cell 1 is moderated under any conditions, and the fluctuation given to the operation is minimized. It is possible to do.

In the above embodiment, hydrogen gas having a purity of approximately 100% is used as a reserve fuel. However, any fuel that can generate power relatively quickly at the start of operation is not necessarily limited to hydrogen gas having a purity of 100%. I can't. Also, in the above embodiment, LP gas or gasoline is used as the main fuel, but other hydrocarbon-based fuels may be used. Also,
The type of the fuel cell 1 and the reformer 7 is not limited to the structure described in the above embodiment, but may be another type or structure.

[0025]

As described in detail above, according to the fuel cell fuel switching method of the present invention, when starting operation, spare fuel is supplied, and then when gradually switching from spare fuel to reformed fuel, The fuzzy control controls the fluctuation of the output of the fuel cell to be moderate, so by gradually switching from the reserve fuel to the reforming fuel, the fluctuation of the output of the fuel cell is moderated. The effect can be minimized.

Further, according to the fuel switching device for a fuel cell of the present invention, the main fuel control valve provided in the reformed fuel supply passage, the spare fuel control valve provided in the spare fuel supply passage,
When switching from the spare fuel to the reformed fuel, the fuzzy control unit that controls the main fuel control valve and the spare fuel control valve is provided so that the output of the fuel cell fluctuates slowly.
The fuzzy control unit controls the reserve fuel control valve and the main fuel control valve, thereby changing the supply ratio of the reserve fuel and the reformed fuel to moderate the fluctuation of the output of the fuel cell, and giving the operation to the operation of an automobile. Impact can be minimized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a fuel switching device for a fuel cell according to the present invention.

FIG. 2 is a view showing a structure of a reformer in the embodiment.

FIG. 3 is a diagram showing a fuzzy control rule in the embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 fuel cell 2 spare fuel tank 3 main fuel tank 4 supply path 5 reserve fuel control valve 6 supply path 7 reformer 8 main fuel control valve 9 fuzzy control unit

Claims (6)

[Claims] 1. A fuel cell switching method for a fuel cell, wherein power is generated by using a spare fuel and a reformed fuel obtained by reforming a main fuel via a reformer, wherein the fuel cell is provided with When supplying fuel and thereafter gradually switching from the reserve fuel to the reformed fuel, the fuel is controlled by fuzzy control so as to reduce fluctuations in the output of the fuel cell. Switching method. 2. The fuel switching method for a fuel cell according to claim 1, wherein the spare fuel is pure hydrogen, and the main fuel is a hydrocarbon-based fuel. . 3. The fuel switching method for a fuel cell according to claim 1, wherein the fuel is gradually switched from the reserve fuel to the reforming fuel while monitoring the output of the fuel cell. Battery fuel switching method. 4. A fuel cell switching device for a fuel cell which generates power using a spare fuel and a reformed fuel obtained by reforming a main fuel via a reformer, wherein a supply path for supplying the spare fuel to the fuel cell. A main fuel control valve provided in a supply path for supplying reformed fuel obtained by reforming the main fuel via a reformer to the fuel cell; and The spare fuel control valve is controlled so that fuel is supplied to the fuel cell, and when the temperature of the reformer rises and reaches a steady state, the fuel is gradually switched from the spare fuel to the reformed fuel. And a fuzzy control unit for controlling the spare fuel control valve and the main fuel control valve so as to reduce fluctuations in the output of the fuel cell. 5. The fuel switching device for a fuel cell according to claim 4, wherein the spare fuel is pure hydrogen, and the main fuel is a hydrocarbon-based fuel. . 6. The fuel switching device for a fuel cell according to claim 4, wherein the fuzzy control unit controls the spare fuel control valve and the main fuel control valve while monitoring an output of the fuel cell. A fuel switching device for a fuel cell, characterized by controlling.