JPH11339821A - Hybrid fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To utilize the merits of both fuel cells and complement the demerits on characteristics and operation by using a phosphoric acid fuel cell as a battery and a hydrogen refining device, and using the phosphoric acid fuel cell and a solid polymer fuel cell for a hydrogen feeding device and a hydrogen storage alloy filling container in common. SOLUTION: A phosphoric acid fuel cell(PAFC) is connected to a hydrogen feeding device at the time of a low power load such as at night, and a polymer electrolyte fuel cell(PEFC) is operated by the high-purity hydrogen obtained here by refining to obtain electric power. When a voltage is applied to the PAFC to give electric power E, the hydrogen-rich gas from the hydrogen feeding device is refined, and the obtained high-purity hydrogen is fed to the PEFC and a hydrogen storage alloy tower (tower filled with a hydrogen storage alloy). Only the required electric power is generated by the PEFC, the extra hydrogen is fed to the hydrogen storage alloy tower and stored, and the hydrogen storage quantity is adjusted according to the load of the PEFC.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hybrid in which a phosphoric acid fuel cell and a polymer electrolyte fuel cell are combined with a hydrogen supply device such as a hydrocarbon-based raw material gas reformer and a hydrogen storage alloy filled container. Fuel cell system.

[0002]

2. Description of the Related Art Fuel cells are classified into a phosphoric acid type, a polymer electrolyte type, a molten carbonate type, a solid electrolyte type, and the like, depending on a difference in a substance used as an ion conductor, that is, an electrolyte.
Each of these fuel cells is configured as a unique system and generates power. Among them, phosphoric acid fuel cell (PAFC)
Is characterized in that the electrolyte is phosphoric acid. The electrolyte is formed by impregnating a porous base material with a concentrated phosphoric acid aqueous solution, for example. A negative electrode (anode = fuel electrode) and a positive electrode (cathode = oxygen electrode or air electrode) are arranged with a porous substrate impregnated with a concentrated phosphoric acid aqueous solution interposed therebetween, and hydrogen gas as fuel is supplied to the negative electrode side Then, power can be taken out by supplying oxygen or air to the positive electrode side to cause an electrochemical reaction.

[0003] FIG. 1 is a diagram for explaining in principle one embodiment of a phosphoric acid type fuel cell. A fuel electrode and an air electrode (an oxygen electrode when oxygen is used as an oxidizing agent) are arranged with an electrolyte impregnated with phosphoric acid therebetween, and a separator is arranged with these being sandwiched. Generates heat when operating as a battery,
Cooling tubes are provided to maintain the battery at a constant operating temperature, such as about 190-210 ° C. Since the voltage of a single electrolyte (single cell) is as low as, for example, about 0.65 to 0.75 V, it is usually configured by stacking a plurality of single cells in series.

[0004] These points are the same in principle for the polymer electrolyte fuel cell, except that the type of electrolyte is different. FIG. 2 is a diagram schematically showing a conventional polymer electrolyte fuel cell system. A hydrocarbon source gas such as city gas is decomposed into a reformed gas containing hydrogen as a main component in a steam reformer. The CO (carbon monoxide) concentration in the reformed gas is 1
vol% or less, the CO of the polymer electrolyte fuel cell
Since the allowable value is 100 ppm or less, CO
pm or less, and then supplied to the polymer electrolyte fuel cell. The operating temperature of the polymer electrolyte fuel cell is about 50 to 100
° C, so that the temperature is controlled within the temperature range by cooling water.

[0005] The phosphoric acid fuel cell (PAFC) and the polymer electrolyte fuel cell (PEFC) each have advantages and disadvantages in terms of their properties. ) To (3). (1) In the case of PAFC, the allowable CO concentration in the fuel hydrogen gas supplied to the battery is 1 vol%. In contrast, P
In the case of EFC, CO needs to be 100 ppm or less. For this reason, PEFC is more complicated than a hydrogen supply device for PAFC (hydrogen supply process). In addition to the hydrogen supply device for PAFC, for example, three or more (multiple) columns of PS
Tower A (Pressure Swing Advisor)
ionTowner) to supply purified hydrogen from which CO has been removed.

(2) In the case of PAFC, it takes a long time to start and stop because the operating temperature of the battery is high, but in the case of PEFC, it can be easily started and stopped because the operating temperature is low. In both cases, it takes time to start and stop the hydrogen supply process. (3) In the case of PAFC, the operating temperature of the battery is about 190 to
Since the temperature is 210 ° C., relatively high-temperature exhaust heat can be recovered, for example, steam can be recovered. On the other hand, in the case of PEFC, since the operating temperature of the battery is about 50 to 100 ° C., the temperature level of the recovered exhaust heat is low, and it can be recovered only with hot water, for example.

[0007]

According to the present invention, a phosphoric acid fuel cell and a polymer electrolyte fuel cell are shared by a hydrogen supply device and a hydrogen storage alloy filled container, By utilizing the refining function, a hybrid fuel cell system that combines the advantages of both fuel cells and complements the characteristics and operational disadvantages of a phosphoric acid fuel cell and a polymer electrolyte fuel cell to complement each other. The purpose is to provide.

[0008]

According to the present invention, (1) a phosphoric acid type fuel cell and a polymer electrolyte fuel cell are juxtaposed in a hydrogen supply device, and the hydrogen-rich gas from the hydrogen supply device is supplied during low power operation. It is supplied to the phosphoric acid type fuel cell for purification, and the obtained high-purity hydrogen is supplied to the polymer electrolyte fuel cell to generate power, and supplied to a hydrogen storage alloy filled container for storage. A hybrid fuel cell system is provided.

Further, the present invention provides (2) a phosphoric acid type fuel cell and a solid polymer type fuel cell provided side by side in a hydrogen supply device, and the hydrogen rich gas from the hydrogen supply device is supplied to the phosphoric acid type fuel during a low power load operation. Supplying the purified high-purity hydrogen to the battery, supplying the obtained high-purity hydrogen to the polymer electrolyte fuel cell to generate electric power, and supplying and storing the high-purity hydrogen to a hydrogen storage alloy filled container; Provided is a hybrid fuel cell system, wherein a secondary cooling system of a battery cooling system of a battery is used as a battery cooling system of a polymer electrolyte fuel cell.

Further, according to the present invention, (3) a phosphoric acid type fuel cell and a polymer electrolyte fuel cell are juxtaposed in a hydrogen supply device, and the hydrogen-rich gas from the hydrogen supply device is supplied to the phosphoric acid type fuel during a low power load operation. The high-purity hydrogen obtained is supplied to the battery and purified, and the obtained high-purity hydrogen is supplied to the polymer electrolyte fuel cell to generate power, and is also supplied to and stored in the hydrogen storage alloy-filled container. A hybrid fuel cell system characterized in that high-purity hydrogen is released from a storage alloy filled container and supplied to a polymer electrolyte fuel cell.

Further, the present invention provides (4) a phosphoric acid type fuel cell and a solid polymer type fuel cell provided side by side in a hydrogen supply device, and the hydrogen-rich gas from the hydrogen supply device is supplied to the phosphoric acid type fuel cell during a low power operation. And purified, and the resulting high-purity hydrogen is supplied to the polymer electrolyte fuel cell to generate power, and is also supplied and stored in a hydrogen storage alloy-filled container, and hydrogen is stored during high-load power operation. High-purity hydrogen is released from the alloy-filled container and supplied to the polymer electrolyte fuel cell, and the secondary cooling system of the cell cooling system of the phosphoric acid fuel cell is used as the cell cooling system of the polymer electrolyte fuel cell A hybrid fuel cell system is provided.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A basic feature of the present invention resides in that a phosphoric acid type fuel cell is used as a cell and also used as a hydrogen purifier.
Further, the phosphoric acid type fuel cell and the hydrogen supply device are not suitable for starting and stopping, and therefore, the
Although it was difficult to take the form of S operation (= Daily Start Stop), in the present invention, this is used as a battery during the day when the load of power generation is high, and as a hydrogen purification device at night when the load of power generation is low. By using the phosphoric acid type fuel cell, the DSS operation mode can be adopted.

In the present invention, the phosphoric acid fuel cell (P
(AFC) and a polymer electrolyte fuel cell (PEFC), which are juxtaposed via a hydrogen supply device. Hydrogen gas can be obtained by various methods. As the hydrogen of the present invention, hydrogen obtained by any method is used. Among them, the steam reforming method using natural gas or city gas containing methane as a main component is particularly preferably applied in the present invention because a relatively abundant and clean gas is used as a raw material.

When the raw material gas is a city gas or the like containing sulfur (S) in mercaptan or other forms, the raw material gas is introduced into a desulfurizer to remove the sulfur contained in the raw material gas. If the source gas contains no sulfur or has already been removed, no desulfurizer is required. The source gas is
The steam from the steam generator is added, mixed and introduced into the reformer, where it is reformed into a hydrogen-rich gas (gas containing hydrogen as a main component).

FIG. 3 is a view schematically showing a reformer, which basically comprises a combustion section and a reforming section. In FIG. 3, F is a fuel supply pipe, and K is an air supply pipe. Ni in the reforming section
A suitable catalyst such as a system or Ru system is used, and the raw material gas is converted into a reformed gas containing hydrogen as a main component by heat ΔH and steam from the combustion unit. In the reformed gas, unreacted steam, unreacted raw material gas, and some CO gas besides CO ₂ are produced as by-products.
Included with it and is optionally passed through a CO converter to convert this by-product CO gas to CO ₂ for removal.

The reaction in the shift converter is represented by the following formula (1). As the H ₂ O in this reaction, unreacted residual steam in the reformer is used. The gas exiting the CO converter is hydrogen (H ₂ ) and carbon dioxide (C
O ₂ ) and unreacted raw material gas.
vol% or less. In the present invention, the CO content is 1 vo
1% or less of reformed gas produced is used as fuel electrode (hydrogen electrode) for PAFC
To supply.

Embedded image CO + H ₂ O = CO ₂ + H ₂ (1)

By the way, PAFC is for obtaining electric power using hydrogen gas as fuel, and FIG. 4 is a view schematically showing the mechanism. For example, when hydrogen is produced by reforming city gas or natural gas and supplied to one electrode, in the phosphoric acid electrolyte, hydrogen molecules release electrons and become hydrogen ions, and the electrons come out. . Therefore, electric power can be obtained by applying a load between the two electrodes. The hydrogen ions remaining in the aqueous solution react with oxygen and electrons sent to the other electrode to generate water.

As described above, PAFC is for obtaining electric power using hydrogen gas as fuel, but can be used for purifying hydrogen if its function is reversed. FIG.
FIG. 2 is a view schematically showing a hydrogen purification mechanism by PAFC. Reforming city gas and natural gas to produce hydrogen, PA
When hydrogen is supplied to the fuel electrode of the FC and a voltage is applied between the two electrodes as shown in the figure, hydrogen is selectively transmitted to the air electrode. That is, in the phosphoric acid electrolyte, the hydrogen molecules release electrons and become hydrogen ions. Free hydrogen ions move to the air electrode and react with electrons to become hydrogen. At this time, H ₂ O, CO, CO ₂ ,
Since CH _{4 and the} like do not pass through, they are discharged as off-gas.

Further, since the hydrogen storage alloy selectively stores hydrogen, in the present invention, the hydrogen storage alloy is used to store the purified hydrogen, and the stored hydrogen is heated at a high load such as during the day. Released and used by The hydrogen storage alloy is not particularly limited as long as it has the characteristics. Examples thereof include TiFe _0.9 Mn _0.1 and Mg ₂
Ni, CaNiS, LaNi ₅ , LaNi _4.7 Al _0.3 ,
MmNi _4.5 Al _0.5 (Mm = Misch metal), MmN
i _4.15 Fe _0.85 (Mm = misch metal).

[0020]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that the present invention is not limited to these Examples. In the following related figures,
A switching valve is appropriately arranged in each fluid pipe, but is not shown in the drawings.

FIG. 6 shows the state when the power is low, such as at night.
This is an example in which a PAFC is connected to a hydrogen supply device, and a PEFC is operated with high-purity hydrogen obtained by purification to obtain electric power. When a voltage is applied to the PAFC to apply the electric power E, the hydrogen-rich gas from the hydrogen supply device is purified by a mechanism as shown in FIG. The obtained high-purity hydrogen is supplied to a PEFC and a hydrogen storage alloy tower (a tower filled with a hydrogen storage alloy).

In the PEFC, a necessary amount of power is generated, and excess hydrogen is supplied to the hydrogen storage alloy tower and stored (the hydrogen storage amount is adjusted according to the load of the PEFC). In addition, PAF
In C, an off-gas consisting of H ₂ O, CO, CO ₂ , CH ₄ and hydrogen which did not contribute to power generation at the anode is generated, and is sent to the fuel or air conduit of the reformer in the hydrogen supply system. Used.

The operating temperature of the PAFC is about 190
The operating temperature of PEFC is about 50-100 ° C, while it is as high as ~ 210 ° C. In the present invention, PAF
The circulating cooling water of the PAFC battery cooling system is used via the heat exchanger A for cooling the battery cooling system of C. In FIG. 6, a heat exchanger B is a heat exchanger for controlling the temperature of the battery cooling system of the PEFC. In the heat exchanger B, water such as cold water is supplied to the battery cooling system of the PEFC. However, the water is taken out as hot water or high-temperature water and can be used as hot water or other hot water.

FIGS. 7 (a) and 7 (b) show an example in which the PAFC and the PEFC are simultaneously operated to obtain the required power during a high power load such as during the day. The arrangement of each device is as shown in FIG. 6, and is switched by operating a valve or the like. Where P
Since the AFC operates at a CO concentration of 1 vol% or less, the reformed gas from the reformer can be used as it is. If the CO concentration exceeds 1 vol% depending on the performance of the reformer, a CO converter may be provided to lower the CO concentration to less than 1 vol%.

For the operation of the PEFC, high-purity hydrogen stored in the hydrogen storage alloy tower is supplied. Since the hydrogen storage alloy absorbs hydrogen with heat generation and releases hydrogen by heating, the hydrogen storage alloy tower needs a configuration for that. FIG. 7C is a diagram showing one example. When storing hydrogen, a heat medium for cooling (for example, cooling water) is introduced from the introduction pipe 3 to remove heat generated at the time of hydrogen storage, and the hydrogen is discharged from the discharge pipe 4 while maintaining the temperature optimal for hydrogen storage.

When releasing the stored high-purity hydrogen, a heating heat medium (for example, hot water or high-temperature water) is introduced from the introduction pipe 3 and discharged from the discharge pipe 4 while maintaining the temperature at an optimum temperature for releasing hydrogen. In FIG. 7C, reference numeral 1 denotes a high-purity hydrogen introduction pipe from the PAFC, and 2 denotes a high-purity hydrogen discharge pipe to the OEFC.

It is desirable to stop the fuel cell at night when the amount of power used at the battery installation site is small.
In AFC, continuous start / stop (DSS operation = Day)
(y Start Stop) is difficult, so that low-load operation was performed despite low power generation efficiency. According to the present invention, by using PAFC as a hydrogen purifier at night, it is not necessary to perform low-load operation, and an operation state with low power generation efficiency can be avoided.

[0028]

According to the present invention, both fuels are used by using PAFC as a battery and as a hydrogen purifier, and by sharing PAFC and PEFC with a hydrogen supply device. The advantages of batteries can be used to complement the characteristics and operational disadvantages of PAFC and PEFC.

According to the present invention, the battery system can be simplified by setting the battery cooling system of the PAFC and the battery cooling system of the PEFC in the same loop, and the initial cost can be reduced. As a result, it is possible to reduce the power of the auxiliary equipment and reduce the running cost. Further according to the invention, P
AFC is used for base load (minimum load) power generation and PEF
By setting C to be used for DDS power generation and selecting the load of each of these batteries so as to match the power load pattern of the battery installation site, a power generation system capable of constantly and efficiently changing the load can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an aspect of a PAFC in principle.

FIG. 2 is a diagram schematically showing an example of an operation mode of PEFC.

FIG. 3 is a diagram schematically showing an example of an embodiment of a hydrogen supply device.

FIG. 4 is a diagram schematically showing a mechanism for obtaining electric power by using hydrogen gas as fuel in PAFC.

FIG. 5 is a diagram schematically showing a hydrogen purification mechanism that reverses the function of a PAFC.

FIG. 6 shows that the PAF is connected to the hydrogen supply device when the power is low.
C and PEFC with high-purity hydrogen obtained here.
The figure which shows the example which obtains electric power by operating a.

FIG. 7 is a diagram showing an example of obtaining electric power by simultaneously operating a PAFC and a PEFC at the time of high power load.

[Explanation of symbols]

 F Fuel conduit K Air conduit 1 High-purity hydrogen inlet pipe from PAFC 2 High-purity hydrogen outlet pipe to PEFC 3 Heat medium inlet pipe 4 Heat medium outlet pipe

Claims (5)

[Claims] 1. A phosphoric acid type fuel cell and a polymer electrolyte fuel cell are juxtaposed in a hydrogen supply device, and a hydrogen-rich gas from the hydrogen supply device is supplied to the phosphoric acid type fuel cell during low-power operation to purify the phosphoric acid fuel cell. A hybrid fuel cell system, characterized in that the obtained high-purity hydrogen is supplied to the polymer electrolyte fuel cell to generate power, and is also supplied to and stored in a hydrogen storage alloy filled container. 2. A phosphoric acid type fuel cell and a solid polymer type fuel cell are juxtaposed in a hydrogen supply device, and a hydrogen rich gas from the hydrogen supply device is supplied to the phosphoric acid type fuel cell during power low load operation to purify the phosphoric acid type fuel cell. Then, the obtained high-purity hydrogen is supplied to the polymer electrolyte fuel cell to generate electric power, and is also supplied to and stored in the hydrogen storage alloy-filled container. A hybrid fuel cell system, wherein the secondary cooling system is a cell cooling system of a polymer electrolyte fuel cell. 3. A phosphoric acid fuel cell and a polymer electrolyte fuel cell are juxtaposed in a hydrogen supply device, and a hydrogen-rich gas from the hydrogen supply device is supplied to the phosphoric acid fuel cell for refining during low-power operation. Then, the obtained high-purity hydrogen is supplied to the polymer electrolyte fuel cell to generate electric power, and is also supplied to and stored in the hydrogen storage alloy-filled container. A hybrid fuel cell system, wherein hydrogen is discharged and supplied to a polymer electrolyte fuel cell. 4. A phosphoric acid type fuel cell and a polymer electrolyte fuel cell are juxtaposed in a hydrogen supply device, and a hydrogen-rich gas from the hydrogen supply device is supplied to the phosphoric acid type fuel cell for refining during low power operation. Then, the obtained high-purity hydrogen is supplied to the polymer electrolyte fuel cell to generate electric power, and is also supplied to and stored in the hydrogen storage alloy-filled container. The hydrogen is released to be supplied to the polymer electrolyte fuel cell, and the secondary cooling system of the cell cooling system of the phosphoric acid fuel cell is used as the cell cooling system of the polymer electrolyte fuel cell. Hybrid fuel cell system. 5. The hybrid fuel cell system according to claim 1, wherein the hydrogen-rich gas is a reformed gas using city gas or natural gas as a source gas.