JP5502521B2 - Fuel cell system - Google Patents

Description

  The present invention includes a hydrogen production apparatus including a reforming unit that reforms while heating raw fuel for hydrogen production and reforming water to generate a hydrogen-rich reformed gas, and consumes the reformed gas to generate power. The present invention relates to a fuel cell system including a generated fuel cell stack and a fuel cell cooling system for cooling the fuel cell stack by circulating cooling water.

  In this type of fuel cell system, as shown in Patent Document 1, cooling water stored in a cooling water tank is circulated through the fuel cell stack to cool the fuel cell stack, After the moisture in the off gas is condensed and collected and stored in the recovered water tank, a part of the recovered water is supplied as reforming water to the reforming section of the hydrogen production apparatus.

JP 2006-40553 A

In Patent Document 1, the number of tanks and pumps is increased, which is disadvantageous in terms of downsizing the system and cost.
In addition, since the recovered water that has become low temperature (normal temperature) due to heat radiation or the like while being stored in the recovered water tank is used as the reforming water, when the reforming water is steamed in the hydrogen production device, More heat is needed. That is, the amount of heat exchanged by the transformer or the selective oxidizer increases. The transformer and the selective oxidizer are suitable for catalyst reaction not only by the heat exchanger that also serves as steam for reforming water, but also by heating means such as exhaust gas from the burner that heats the heater and reformer. Therefore, if a large amount of heat is lost due to the steaming of the reforming water by heat exchange, it is necessary to increase the amount of fuel supplied to the heater and burner, leading to a decrease in hydrogen production efficiency. It was.

Furthermore, the recovered water from the recovered water tank is replenished to the cooling water tank in the fuel cell cooling system via a pump. In this configuration, the recovered water tank is stored in the recovered water tank and radiated to a low temperature (normal temperature). Since the water which became becomes intermittently supplied in a cooling water tank, the water temperature in a cooling water tank falls rapidly and there exists a possibility that a battery voltage may fall.
In addition, fluctuations in the water temperature of the reforming water supplied to the reformer lead to temperature changes in the converter and the selective oxidation unit, which in turn leads to deterioration of the catalyst. In order to keep the range, it is necessary to frequently control the hydrogen production apparatus, leading to a reduction in the life of the hydrogen production apparatus.

In addition, driving the pump that supplies the recovered water to the cooling water tank causes an increase in power consumption in the fuel cell system, leading to a decrease in power generation efficiency.
The present invention has been made paying attention to such a conventional problem, and an object of the present invention is to provide a fuel cell system that is compact and promotes cost reduction and that increases the operating efficiency of each part of the system.

For this reason, the present invention is produced by a hydrogen production apparatus including a reforming unit that reforms while heating raw hydrogen fuel and reforming water to produce a hydrogen-rich reformed gas, and the hydrogen production apparatus. A fuel cell stack that consumes reformed gas to generate electric power, and a heat exchanger between an outlet of the fuel cell stack and a water tank, and circulates cooling water through the fuel cell stack so as to circulate the fuel cell stack. A fuel cell cooling system that cools the cooling water with the heat exchanger and then cools the cooling water with the heat exchanger. The fuel cell system includes the following configuration.

While the water tank is configured with a single water tank that stores cooling water and is directly replenished with water collected by a part of the fuel cell system,
Connecting said portion of the water that circulates through the fuel cell cooling system, the pre-Symbol reforming water supply system for supplying to the reforming section as a reforming water, between the heat exchanger and the outlet of the fuel cell stack did.

Since only one water tank is required and the water tank does not require a complicated structure, the layout of the system can be made compact and the manufacturing cost can be reduced.
In addition, since a part of the high-temperature cooling water circulating in the fuel cell cooling system is supplied to the reforming section as reforming water, the amount of heat required for steaming the reforming water can be reduced, and the hydrogen production efficiency Can be increased.

  Furthermore, since water collected from a part of the system is directly replenished into the water tank, rapid fluctuations in water temperature can be suppressed, so there is no need to provide a heater for the water tank. The power generation efficiency of the fuel cell system can be increased by eliminating the drive of the pump that supplies water to the cooling water tank. Moreover, the control load of the hydrogen production apparatus is reduced, and the life of the hydrogen production apparatus can be extended.

1 is a block diagram showing an outline of a fuel cell system according to an embodiment of the present invention. The block diagram which shows the outline of the fuel cell system which concerns on embodiment which changed a part of embodiment same as the above.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing an outline of a fuel cell system according to an embodiment of the present invention.
The raw fuel pump 1 for hydrogen production is a raw fuel that is reformed and generates hydrogen gas as will be described later, for example, a liquid fuel such as kerosene and methanol, a gaseous fuel such as natural gas and methane gas, and the like. The contained fuel is supplied to the reforming unit 21 of the hydrogen production apparatus 2. When the raw fuel contains a sulfur component, a desulfurization device is provided, and after the sulfur component is removed from the raw fuel through the desulfurization device, the raw fuel is supplied to the reforming unit 21.

The hydrogen production apparatus 2 includes the reforming unit 21 and a CO removal unit 24 including a transformer 22 and a selective oxidizer 23.
The reforming unit 21 includes a reforming catalyst that promotes a reforming reaction, and is supplied in a state in which the raw fuel from the raw fuel pump 1 and the reforming water are mixed, and reforms rich in hydrogen by the reforming reaction. Generate gas.

  Since this reforming reaction is an endothermic reaction, the reformer 21 is integrally provided with a burner 21a, and the reforming fuel is burned with the combustion fuel supplied from the burner combustion fuel pump 3 and reformed. The part 21 is heated to promote the reforming reaction. The combustion fuel may be the same as the raw fuel for hydrogen production, but a different fuel may be used, and after generation of the reformed gas, it is switched to surplus off-gas from the anode of the fuel cell stack to be described later. Use together.

The transformer 22 of the CO removal unit 24 reduces the carbon monoxide concentration in the reformed gas that has passed through the reforming unit 21 by a shift reaction.
The selective oxidizer 23 of the CO removing unit 24 further reduces the concentration of carbon monoxide in the reformed gas that has passed through the converter 22 by an oxidation reaction, and reduces hydrogen and other impurities to an allowable value or less. Use gas.

The reformed gas obtained by the hydrogen production apparatus 2 in this way is supplied to the anode 4a of the polymer electrolyte fuel cell (hereinafter referred to as PEFC) stack 4.
The PEFC stack 4 is configured by stacking a plurality of battery cells (not shown), generates electric power using the reformed gas, and outputs a DC current. The battery cell has an anode, a cathode, and a polymer electrolyte membrane disposed between the anode and the cathode. Each battery cell is introduced by introducing reformed gas into the anode and air into the cathode. In this case, an electrochemical power generation reaction is performed.

In addition, since the PEFC stack 4 generates heat in response to a power generation reaction, a fuel cell cooling system that circulates and cools cooling water is disposed as follows.
The water tank 5 and the PEFC stack 4 are connected by a first cooling water pipe 8 having a cooling water pump 6 and an ion exchange resin 7 interposed therebetween, and heat exchange is performed between the PEFC stack 4 and the water tank 5. It connects by the 2nd cooling water piping 10 which interposed the container 9. As shown in FIG.

  Cooling water stored in the water tank 5 is sucked and discharged by the cooling water pump 6 to remove impurities through the ion exchange resin 7 to obtain pure water, and then circulates in the PEFC stack 4 so that the PEFC stack 4 is Cooling. The cooling water flowing out of the PEFC stack 4 is cooled by exchanging heat with hot water stored and circulated in a hot water storage tank (not shown) via the heat exchanger 9 and then returned to the water tank 5.

A part of the cooling water is taken out from the fuel cell cooling system and used as reforming water.
In the first embodiment, the reforming water pump 11 is installed at a position of the second cooling water pipe 10 between the PEFC stack 4 and the heat exchanger 9 that are at a higher temperature in the fuel cell cooling system. The inlet of the quality water pipe 12 is connected, and the outlet of the reforming water pipe 12 is connected to the reforming section 21 of the hydrogen production apparatus 2.

  The reforming water in the reforming water pipe 12 is heat exchanger 13 for exchanging heat with the exhaust gas from the burner 21 a of the reforming section 21, and each heat exchanging section in the selective oxidizer 23 and the transformer 22. Heated while passing through 23 a and 22 a, at least part of the steam is supplied to the reforming unit 21 as steam. Note that the temperatures of the selective oxidizer 23 and the transformer 22 are the heat exchange portions (not shown) and the heater (not shown) with the burner exhaust gas for heating the reformer, in addition to the heat exchange portions 23a and 22a. It is controlled so as to be in a suitable temperature range by a heating means such as.

Water collected from a part of the fuel cell system is directly supplied into the water tank 5 of the fuel cell cooling system. The water supply system is configured as follows.
A first recovered water pipe 14 is provided that guides water generated by the reaction at the cathode of the PEFC stack 4 from the cathode 4b to the water tank 5 as recovered water.
In addition, as described above, after the reformed gas is generated from the hydrogen production apparatus 2, the anode offgas pipe 15 is provided to supply the surplus offgas from the anode of the fuel cell stack to the burner 21a. A heat exchanger 16 for exchanging heat of the off gas with the cooling water of the fuel cell cooling system is disposed in the middle of the pipe 15. Then, a second recovered water pipe 17 is provided that guides the condensed water obtained by condensing the moisture in the offgas in the heat exchanger 16 from the drain port of the heat exchanger 16 to the water tank 5 as recovered water.

Further, a heat exchanger 19 for exchanging heat with the cooling water of the fuel cell cooling system is disposed in the middle of the exhaust gas pipe 18 for discharging the exhaust gas from the burner 21a. Furthermore, a third recovered water pipe 20 is provided for guiding condensed water obtained by condensing moisture in the exhaust gas in the heat exchanger 18 from the drain port of the heat exchanger 18 to the water tank 5 as recovered water.
Furthermore, a water supply pipe 31 for supplying water (normal temperature water) to the water tank 5 is provided. An opening / closing valve 32 is interposed in the water supply pipe 31.

  Normally, a sufficient amount of water can be stored in the water tank 5 by replenishing with the recovered water from each of the above parts. However, if for some reason the water in the water tank 5 is insufficient, the on-off valve 32 is provided. The water supply pipe 21 can be opened and replenished with water, and water can be supplied from the water replenishment pipe 21 to the water tank 5 emptied during maintenance or the like. The water supply pipe 21 is not limited to tap water but can be used as a pure water supply pipe.

On the other hand, a cathode offgas pipe 33 that guides a part of the offgas mainly composed of excess air from the cathode into the water of the water tank 5 is disposed in the PEFC stack 4 to perform bubbling.
Hereinafter, effects of the first embodiment will be described.
First, a water tank 5 and one water tank 5 which do not require a complicated structure without requiring a conventional replenishing water tank and a replenishing pump from the recovered water tank to the cooling water tank, and a replenishment control, etc. Since it is only necessary to perform simple control using the cooling water pump 6, the system can be made compact and the manufacturing cost can be greatly reduced.

  Further, since the high-temperature (about 70 degrees) cooling water taken out from the fuel cell cooling system is supplied to the reforming unit 21 as reforming water, low-temperature water (normal temperature water) such as clean water or recovered water is used as it is. Compared to the case of using as reforming water, the amount of heat required for steaming the reforming water, that is, the amount of fuel supplied to the heater and the burner can be greatly reduced, and the hydrogen production efficiency can be improved. .

In particular, in the first embodiment, since the hottest water between the outlet of the PEFC stack 4 and the heat exchangers 9 and 16 is taken out as reforming water, the amount of heat required for steaming the reforming water is reduced. It can be reduced to the maximum.
Further, by directly replenishing the water tank 5 of the fuel cell cooling system with the recovered water from each part of the system, the heat loss of the recovered water generated when the recovered water tank is provided individually, Water temperature fluctuation due to replenishment can be suppressed. Comparing the amount of recovered water flowing into the water tank and the amount of cooling water in a certain time, the amount of cooling water is sufficiently large, so it is always more than replenishing the cooling water tank after it is stored in a certain amount in the recovered water tank. This is because the effect of directly replenishing the cooling water tank on the cooling water is small.

Thereby, the water temperature of the reforming water supplied to the hydrogen production apparatus becomes stable, and the control load of the hydrogen production apparatus can be reduced. Further, the power generation operation of the PEFC stack 4 can be stabilized without providing a heater for the water tank.
In addition, by providing the ion exchange resin 7 between the outlet of the water tank 5 and the PEFC stack 4, metal ions caused by various water pipes and separators constituting the PEFC stack 4 or water supply were performed. High-purity pure water from which silica and other impurities contained in the case are removed can be used as the reforming water, and can be circulated in the fuel cell cooling system.

For this reason, deterioration of the reforming catalyst and an increase in the conductivity of the cooling water that causes a leakage current in the PEFC stack 4 are suppressed, and a separator (not shown) constituting the PEFC stack 4, the cooling water pipe 8, 10. It is possible to reduce the blocking of the reforming water pipe 12, the cooling water pipes 8, 10 and the recovered water pipes 14, 17, 20 and the failure of the cooling water pump 6 and the reforming water pump 11.
In addition, the water in the water tank 5 may contain a large amount of carbon dioxide or the like due to replenishment of recovered water. In this embodiment, at least a part of the off-gas mainly composed of air from the cathode 4b is used as the water tank. By conducting bubbling by guiding it into the water in the water, carbon dioxide in the water can be released as much as possible. The water tank 5 is formed with a gas vent for discharging the gas released from the water tank 5.

As a result, damage to the ion exchange resin 7 caused by acidic water containing carbon dioxide can be suppressed. As a result, failure of the PEFC stack 4 and the cooling water pump 6 due to water containing metal ions and impurities, and further, the reforming water pipe 12. And the deterioration of the reforming catalyst can be suppressed.
FIG. 2 shows a reference example .
In this reference example, the inlet of the reforming water pipe 12 is connected to a position between the outlet of the water tank 5 of the first cooling water pipe 8 and the inlet of the PEFC stack 4 and is taken out as reforming water therefrom. To do.

When the cooling water circulates in the PEFC stack 4, air (oxygen) may be contained in the cooling water if the PEFC stack is not sufficiently airtight. Since water that does not contain air (oxygen) before entering can be supplied to the reformer, oxidative deterioration of the reforming catalyst due to air (oxygen) can be suppressed.
In addition, since the reforming water can be supplied at a moderately high temperature after the heat exchange by the heat exchangers 9 and 16 and at a more stable temperature, heat can be generated in the selective oxidizer 23a and the transformer 22a for steaming the reforming water. The amount of heat exchanged is stabilized, the control load of the hydrogen production apparatus 2 is further reduced, and the life of the hydrogen production apparatus can be extended.

Furthermore, in this reference example, the inlet of the reforming water pipe 12 is connected to a position between the ion exchange resin 7 and the PEFC stack 4 downstream from the outlet of the water tank 5, so Since pure water having higher purity immediately after removal of impurities and impurities can be supplied as reforming water, deterioration of the reforming catalyst due to metal ions and impurities, failure of the reforming pump 11, reforming water piping 12 Can be more effectively suppressed.

  Here, when a separate recovery water tank is provided and the recovery water from the recovery water tank is supplied as reforming water as in the conventional case, if the same effect is to be obtained, the fuel cell cooling system and the reforming water supply It is necessary to arrange two ion exchange resins, one for each system. On the other hand, in the second embodiment, only one ion exchange resin may be provided, and the system can be further reduced in size and cost.

  Although the embodiments of the present invention have been described above with reference to the drawings, the illustrated embodiments are merely illustrative of the present invention, and the present invention is not limited to those shown directly by the described embodiments. It goes without saying that various modifications and changes made by those skilled in the art are included within the scope of the claims.

DESCRIPTION OF SYMBOLS 1 ... Raw fuel pump for hydrogen production 2 ... Hydrogen production apparatus 3 ... Fuel pump for burner combustion 4 ... PEFC stack 5 ... Cooling water tank 6 ... Cooling water pump 7 ... Ion exchange resin 8 ... First cooling water piping 9 ... Heat exchange Apparatus 10 ... Second cooling water pipe 11 ... Reforming water pump 12 ... Reforming water pipe 13 ... Heat exchanger 14 ... First recovered water pipe 15 ... Anode off-gas pipe 16 ... Heat exchanger 17 ... Second recovered water pipe 18 ... exhaust gas pipe 19 ... heat exchanger 20 ... third recovered water pipe 21 ... reforming section 22 ... transformer 23 ... selective oxidizer 24 ... CO removal section 31 ... water supply pipe 32 ... open / close valve 33 ... cathode off-gas pipe

Claims (4)

A hydrogen production apparatus including a reforming section that reforms while heating raw fuel for hydrogen production and reforming water to produce a hydrogen-rich reformed gas;
A fuel cell stack that consumes the reformed gas produced by the hydrogen production apparatus and generates electric power;
A heat exchanger is provided between an outlet of the fuel cell stack and a water tank, cooling water is circulated through the fuel cell stack to cool the fuel cell stack with the cooling water, and then the heat exchange is performed on the cooling water. A fuel cell cooling system that is cooled by a vessel ,
A fuel cell system comprising:
While the water tank is configured with a single water tank that stores cooling water and is directly replenished with water collected by a part of the fuel cell system,
A reforming water supply system for supplying a part of the water circulating through the fuel cell cooling system to the reforming section as the reforming water is connected between the outlet of the fuel cell stack and the heat exchanger. A fuel cell system.   The fuel cell system according to claim 1, further comprising an ion exchange resin between an outlet of the water tank and an inlet of the fuel cell stack.   The water recovered in a part of the fuel cell system includes water generated in the fuel cell stack, water condensed water in the off-gas of the fuel cell stack, and a burner that heats the reforming unit of the hydrogen production apparatus. The fuel cell system according to claim 1 or 2, comprising at least one or more of water condensed from moisture in the exhaust gas. The fuel cell system according to any one of claims 1 to 3, wherein bubbling is performed by introducing at least a part of an off gas mainly air from a cathode of the fuel cell system into the water of the water tank .

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