JP2002216830A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve efficiency of a fuel cell system. SOLUTION: A reformer (4) for generating reformed gas from evaporated fuel, and a fuel cell (5) generating power with the reformed gas are provided, of which, maximum reformed gas generating volume of the reformer (4) is adjusted to be almost same as the volume of reformed gas necessary for power generation of the fuel cell (5) in a steady operation zone. The reformer (4) attains maximum efficiency in an operation at the steady operation zone, improving efficiency as the fuel cell system as well as substantial running mileage of a vehicle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a fuel cell system for generating electric power by using both a reformer and gaseous fuel from a cylinder.

[0002]

2. Description of the Related Art As an example of a conventional fuel cell system,
There is one described in JP-A-9-266006.

[0003]

However, in the above-mentioned fuel cell system, hydrogen is supplied from the cylinder when the load is increased. This hydrogen is simultaneously supplied with the increased load to increase the reformable portion of the reformer. Used for heating. In other words, since it is used as a temporary auxiliary fuel to increase the amount of reformed gas generated, when applied to a simple system in which the reformer is not a variable capacity type, a large capacity reformer can be used with a low load. , The operation of the reformer becomes inefficient, and the system efficiency is reduced.

Accordingly, an object of the present invention is to provide a fuel cell system which solves the above-mentioned problems.

[0005]

According to a first aspect of the present invention, there is provided a fuel cell system comprising a reformer for generating a reformed gas from a vaporized fuel, and a fuel cell for generating electric power using the reformed gas. The maximum reformed gas generation amount of the reformer was set to be substantially equal to the reformed gas amount required for power generation of the fuel cell in the steady operation region.

According to a second aspect of the present invention, in the first aspect, a hydrogen storage device for storing high-concentration hydrogen is provided, and the hydrogen storage device supplies hydrogen to the fuel cell when the load exceeds a load in a normal operation range. I made it.

In a third aspect based on the second aspect, the reformer supplies a maximum amount of reformed gas to the fuel cell at the time of a high load exceeding the load in the steady operation range, and stores the shortage in hydrogen. It was made up with hydrogen from the device.

In a fourth aspect based on the first aspect, a hydrogen storage device for storing high-concentration hydrogen is provided, and when the load is lower than the load in a steady operation range, the maximum amount of reformed gas generated by the reformer is provided. And supply the required amount to the fuel cell,
The surplus reformed gas is stored in the hydrogen storage device.

In a fifth aspect based on the first aspect, an air supply device for supplying air to the fuel cell, a driving device for driving the air supply device, and a part of the reformed gas generated by the reformer are provided. The compression device is driven by a driving device, and the compressed reformed gas is stored in the hydrogen storage device.

According to a sixth aspect of the present invention, in the second or third aspect, there is provided a carbon monoxide removing apparatus for removing a carbon monoxide concentration in a reformed gas to a level not more than an allowable carbon monoxide concentration used for power generation in a fuel cell. When the reformed gas from the reformer and the hydrogen from the hydrogen storage device are simultaneously supplied to the fuel cell, the carbon monoxide concentration of the mixed gas of the reformed gas and hydrogen can be supplied to the fuel cell. Air is supplied to the carbon monoxide removing device so that the concentration becomes equal.

According to a seventh aspect of the present invention, in the second or third aspect, when the reformed gas from the reformer and the hydrogen from the hydrogen storage device are simultaneously supplied to the fuel cell, the reformed gas and the hydrogen in the fuel cell are supplied. The stoichiometric ratio of the mixed gas is made smaller than that of only the reformed gas in accordance with the mixing ratio of hydrogen.

[0012]

According to the first aspect of the present invention, since the reformer having the maximum reformed gas generation amount in the steady operation region is provided, the operation of the reformer in the steady operation region has the maximum efficiency, and the fuel cell system has As a result, the fuel efficiency of the vehicle can be substantially improved, and the actual fuel efficiency of the vehicle can be improved. In addition, since a reformer that generates the maximum amount of reformed gas is used in the steady operation range, the reformer can be downsized without unnecessarily increasing the capacity of the reformer. The period can be shortened.

In the second invention, a hydrogen storage device for storing high-concentration hydrogen is provided, and when the load is higher than the load in the normal operation range, hydrogen is supplied from the hydrogen storage device to the fuel cell. High load can be accommodated without increasing the size of the vessel.

According to a third aspect of the present invention, at the time of a high load exceeding a load in a steady operation range, the reformer supplies the maximum amount of reformed gas to the fuel cell and makes up the shortage with hydrogen from the hydrogen storage device. As a result, the reformer can be operated in a high efficiency state even in a high load range, and the efficiency of the fuel cell system can be improved.

In a fourth aspect of the present invention, when the load is lower than the load in the steady operation region, the reformer generates the maximum amount of reformed gas to supply the necessary amount to the fuel cell and to reform the surplus. Since the gas is stored in the hydrogen storage device, the reformer can be operated near the maximum efficiency, and the efficiency of the fuel cell system can be improved.

In addition, since the hydrogen storage device is supplemented with reformed gas from the reformer in addition to hydrogen filling from the outside,
Even with the same capacity of the hydrogen storage device, the hydrogen supply time from the hydrogen storage device can be extended, and the driving distance of a fuel cell driven vehicle can be extended.

According to a fifth aspect of the present invention, the compression device for compressing the reformed gas is driven by the driving device of the air supply device. Therefore, in addition to the effect of the fourth invention, the driving device of the compression device is supplied with the air supply device. Since it can be shared with the device, there is no need to install a drive device for the compression device again, and mounting on the vehicle becomes easy.

In the sixth invention, when removing carbon monoxide by an oxidation reaction in a carbon monoxide removing device, usually, oxygen is supplied several times as much as carbon monoxide to the carbon monoxide removing device. In addition to carbon, hydrogen reacts with oxygen to reduce the amount of hydrogen in the reformed gas supplied to the fuel cell. In the present invention, however, the reformed gas supplied to the fuel cell is diluted with hydrogen, so The concentration of carbon monoxide in the reformed gas discharged from the carbon removal device may be high, and as a result, the amount of air supplied to the carbon monoxide removal device is reduced, and the amount of hydrogen consumed by the carbon monoxide removal device is reduced. Can be reduced. Therefore, the amount of hydrogen in the reformed gas discharged from the carbon monoxide removing device can be increased, and the efficiency of the fuel cell system can be improved.

In the seventh invention, the stoichiometric ratio of the reformed gas to the pure hydrogen is generally increased in order to secure the hydrogen partial pressure in the fuel cell required for the reaction. When the hydrogen from the hydrogen storage device is simultaneously supplied to the fuel cell, the stoichiometric ratio of the mixed gas of the reformed gas and the hydrogen in the fuel cell is made smaller than the case of the reformed gas alone according to the mixing ratio of the hydrogen. The amount of hydrogen supplied to the fuel cell can be reduced, and the efficiency of the fuel cell system can be improved.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the accompanying drawings.

Referring to FIG. 1, the present fuel cell system includes a reformer 4 for generating a hydrogen-rich reformed gas based on vaporized fuel and water, and a carbon monoxide (hereinafter, referred to as a reformed gas) in the reformed gas. , CO), a fuel cell 2 that generates electric power based on the reformed gas supplied from the CO removal device 5 and the air supplied from the compressor 7, and a fuel cell. A combustor 1 that burns exhaust hydrogen and exhaust air discharged from the fuel cell 2, and a fuel and water supplied from a tank are vaporized by using heat of the combustion gas from the combustor 1 to convert the vaporized fuel into a reformer. And an evaporator 3 for supplying the evaporator 3 to the evaporator 3.
The combustion gas which has vaporized the fuel and water is discharged from the evaporator 3 to the outside.

The fuel cell system of the present embodiment further includes a cylinder 10 which is a hydrogen storage device for supplying hydrogen required for power generation of the fuel cell 2. The hydrogen supplied from the cylinder 10 is a sufficiently high concentration of hydrogen that can be used for power generation of the fuel cell 2, in other words, the concentration of carbon monoxide in the hydrogen is controlled to a low concentration.

The hydrogen storage device is not limited to the cylinder 10, but may be a hydrogen storage device provided with a hydrogen storage alloy or the like.

A pressure regulating valve 11 for regulating the pressure of hydrogen from the cylinder 10 and a switching valve 15 for controlling the supply of hydrogen from the cylinder 10 are provided between the cylinder 10 and the fuel cell 2. The cylinder 10 further includes an on-off valve 12 that is opened when refilling hydrogen from the outside (not shown).

A switching valve 16 for controlling the supply of the reformed gas to the fuel cell 2 is provided between the CO removing device 5 and the fuel cell 2.
Is provided.

Here, the reformer 4 of the present embodiment determines the maximum amount of reformed gas generated by the reformed gas amount required by the power generation amount of the fuel cell 2 in the steady operation range of the fuel cell system. It is a small reformer set to have the maximum generation amount, and supplies the reformed gas of the maximum generation amount of the reformer 4 to the fuel cell 2 in the operation range with a load exceeding the steady operation range. The shortage is compensated for by supplying hydrogen from the cylinder 10 to the fuel cell 2.

As described above, in this embodiment, as shown in FIG. 2, since the reformer 4 is provided so as to have the maximum efficiency, that is, the maximum reformed gas generation amount under the load in the steady operation range, the efficiency of the reformer is reduced. This can improve the efficiency of the fuel cell system as a result.

Next, the operating states of the reformer 4 and the cylinder 10 will be described for each load condition range of the fuel cell system.

First, when the fuel cell system is operated in the steady operation range, the required amount of the reformed gas required for power generation of the fuel cell 2 is almost the same as the maximum reformed gas generation amount of the reformer 4. The entire amount of gas can be supplied by the reformer 4. Therefore, since the reformer 4 can be operated at the maximum efficiency, the efficiency of the fuel cell system is improved, and the actual fuel efficiency of the vehicle can be improved. Further, since the reformer 4 having the maximum reformed gas generation amount in the steady operation region is used, the capacity of the reformer 4 can be set small, and the reformer 4 can be downsized. Therefore, the start-up and response time of the reformer 4 can be shortened.

When operating with a load exceeding the steady operation range
(For example, at the time of starting the vehicle or at the time of overtaking acceleration), the supply of the reformed gas from the reformer 4 alone results in a shortage of the reformed gas required for power generation, and the insufficient reformed gas is supplied from the cylinder 10. Make up with hydrogen supply.

Therefore, since the reformer 4 can be operated at the maximum efficiency, the efficiency of the fuel cell system is improved, and the shortage of the reformed gas is compensated by the hydrogen from the cylinder 10 at the time of start-up or acceleration. So you can
The response of the reformer 4 does not have to be quick, and the control of the reformer 4 is simplified.

Next, the reformed gas from the reformer 4 and the cylinder 10
The control at the time of simultaneously supplying hydrogen from the furnace will be described.

When the reformed gas and the hydrogen are supplied simultaneously, the mixed gas of the reformed gas and the hydrogen to the CO removing device 5
The concentration may be equal to or less than the same as the CO concentration of only the reformed gas. In order to adjust the CO concentration, the amount of air supplied from the compressor 7 to the CO removing device 5 is adjusted.

In the CO removing device 5, CO is removed by the following reaction.
Is removed.

2CO + O ₂ → 2CO _{2 In} this case, the selectivity of the catalyst is low, and 2 moles of H ₂ are consumed to remove 1 mole of CO. Actually, C in the reformed gas
When O is 2% and this is reduced to the CO concentration (100 ppm or less) permitted by the fuel cell 2 by the CO removing device 5, the oxygen amount is controlled to a flow rate that is about three times the CO flow rate.

In the present embodiment, since the reformed gas discharged from the CO removing device 5 is mixed with hydrogen from the cylinder 10, the amount of CO removed by the CO removing device 5 is reduced, and as a result, CO is removed. possible to reduce the amount of air supplied to the device 5, thus can be reduced with H ₂ amount consumed by the CO remover 5, effectively available H ₂ amount is more efficient to increase the overall system.

When simultaneously supplying the reformed gas and the hydrogen, the stoichiometric ratio of the mixed gas of the reformed gas and the hydrogen in the fuel cell 2 (ie, the flow rate multiple required for the operation with respect to the amount of hydrogen required for the reaction) is determined. In addition, control is performed so as to be smaller in accordance with the mixing ratio of high-concentration hydrogen than when only the reformed gas is used.
The higher the mixing ratio of high-concentration hydrogen in the reformed gas, the higher the hydrogen partial pressure in the fuel cell 2. Therefore, the higher the mixing ratio of high-concentration hydrogen, the smaller the stoichiometric ratio of the mixed gas can be. . Therefore, by controlling the stoichiometric ratio to be small according to the mixing ratio of the high-concentration hydrogen, the amount of hydrogen supplied to the fuel cell 2 can be reduced, and the efficiency of the fuel cell system can be improved.

Next, a second embodiment shown in FIG. 3 will be described.

This is in addition to the configuration of the first embodiment shown in FIG.
Is provided with a reformed gas compression device 17 driven by a motor 8 for driving the gas. The reformed gas compressed by the reformed gas compression device 17 can be supplied to the cylinder 10.

Generally, the efficiency of the reformer 4 increases as the load increases due to the influence of heat radiation to the outside, while the efficiency of the fuel cell 2 increases as the load decreases. Since the efficiency of the system is substantially determined by the efficiency of the reformer 4 and the fuel cell 2, the reforming efficiency of the reformer 4 is low and the efficiency of the system is reduced in a low load region used in a steady operation. .

That is, by improving the efficiency of the reformer 4 in the low load region, the efficiency in the low load region where the fuel cell system is frequently used can be improved, and the substantial fuel efficiency of the vehicle can be improved.

Here, the reformed gas compressor 17 is only used when the output of the fuel cell is small in the low load region where the load is smaller than the steady operation region, the load on the compressor 7 is small, and the output of the motor 8 has a margin. It works. The reformer 4 generates the reformed gas to be supplied to the cylinder 10 in addition to the supply of the reformed gas to the fuel cell 2. That is, the reformer 4 generates a substantially maximum reformed gas generation amount in the same manner as in the steady operation range, but exceeds the reformed gas amount required by the fuel cell 2, and the generation amount becomes excessive. This excess is compressed by the reformed gas compression device 17 and supplied to the cylinder 10.

With this configuration, when the load on the compressor 7 is small and the output of the fuel cell 2 is small, the load on the reformer 4 is also small and the efficiency is reduced. By generating the reformed gas to be supplied to the cylinder 10 in addition to the reformed gas amount to be performed, the reformer 4 can be operated near the maximum efficiency, and the efficiency of the system can be improved. Here, the compressor 7 can drive the reformed gas compression device 17 because the load of the motor 8 has a margin.

Since the cylinder 10 is filled with reformed gas from the reformer 4 in addition to the filling of hydrogen from the outside, the hydrogen supply time from the cylinder 10 can be extended even if the capacity of the cylinder 10 is the same. And the driving distance of the vehicle can be extended.

When regenerative braking is performed by a drive motor (not shown) during vehicle braking in which the load on the fuel cell 2 is reduced, the recovery rate of regenerative energy is reduced if the capacity of the secondary battery is small. In the embodiment, even when the load of the fuel cell 2 is small, power is consumed by the relatively large OLE_LINK1 reformed gas compressor 17 OLE_LINK1, so that the reformed gas compressor 17 is operated to increase the recovery rate of regenerative energy. Can be. Therefore, the fuel efficiency of the fuel cell vehicle can be substantially improved.

Further, since the motor 8 for driving the reformed gas compression device 17 can be shared with the compressor 7, there is no need to install a motor for driving the reformed gas compression device 17 again, and the Mounting becomes easy.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 is an explanatory view showing setting of a reformer capacity.

FIG. 3 is a configuration diagram showing a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustor 2 Fuel cell 3 Evaporator 4 Reformer 5 Carbon monoxide removal apparatus 7 Compressor 10 Cylinder

Claims (7)

[Claims] 1. A fuel cell system comprising: a reformer that generates a reformed gas from a vaporized fuel; and a fuel cell that generates electric power using the reformed gas. Is set to be substantially equal to the amount of reformed gas required for power generation of the fuel cell in a steady operation range. 2. A hydrogen storage device for storing high-concentration hydrogen, wherein hydrogen is supplied from the hydrogen storage device to the fuel cell when the load exceeds a load in a normal operation range. 3. The fuel cell system according to item 1. 3. When the load is higher than the load in the steady operation range, the reformer supplies the maximum amount of reformed gas to the fuel cell and makes up the shortage with hydrogen from the hydrogen storage device. The fuel cell system according to claim 2, wherein: 4. A hydrogen storage device for storing high-concentration hydrogen is provided. When the load is lower than the load in a steady operation range, the reformer generates the maximum amount of reformed gas to reduce the amount required for the fuel cell. 2. The fuel cell system according to claim 1, wherein the excess reformed gas is stored in the hydrogen storage device while being supplied. 3. 5. A compression device comprising: an air supply device for supplying air to a fuel cell; a driving device for driving the air supply device; and a compression device for compressing a part of the reformed gas generated by the reformer. The fuel cell system according to claim 1, wherein the fuel cell system is driven by a driving device, and uses a cylinder as the hydrogen storage device, and stores the compressed reformed gas in the hydrogen storage device. 6. A device for removing carbon monoxide in a reformed gas to a concentration equal to or lower than an allowable carbon monoxide concentration used for power generation in a fuel cell, wherein the reformed gas and hydrogen from a reformer are provided. When hydrogen from the storage device is simultaneously supplied to the fuel cell, air is supplied to the carbon monoxide removal device so that the carbon monoxide concentration of the mixed gas of the reformed gas and hydrogen becomes an allowable carbon monoxide concentration that can be supplied to the fuel cell. 4. The fuel cell system according to claim 2, wherein: 7. When the reformed gas from the reformer and the hydrogen from the hydrogen storage device are simultaneously supplied to the fuel cell, the stoichiometric ratio of the mixed gas of the reformed gas and hydrogen in the fuel cell is changed to the mixing ratio of hydrogen. 4. The fuel cell system according to claim 2, wherein the fuel cell system is made smaller than the case of using only the reformed gas.