JP2002367640A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the maintenance property of an ion removing filter installed to a fuel cell system. SOLUTION: For the fuel cell system having a fuel cell (17) and filters (6, 7) removing impurity ion contained in the water supplied to the fuel cell, an electrochemical filter composed of a cooling water phase side electrode (2) and an absorption phase side electrode (4) having and an ion absorption phase (3), is used as the ion removing filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell system, and more particularly to an improvement in a polymer electrolyte fuel cell system provided with a filter for removing impurities from cooling water.

[0002]

2. Description of the Related Art In recent years, in view of environmental problems, particularly from the viewpoints of air pollution due to exhaust gas from automobiles and global warming due to carbon dioxide, excellent exhaust performance and a fuel using a fuel cell as a power source capable of highly efficient energy conversion. Battery vehicles are attracting attention.

A fuel cell is an energy conversion system that supplies hydrogen or a hydrogen-rich reformed gas and oxygen to cause an electrochemical reaction to convert chemical energy into electric energy.

[0004] Fuel cells are usually operated at an appropriate temperature (80 ° C).
The temperature is controlled by the cooling water so as to maintain the temperature (before and after), and it is necessary to supply pure water of high purity in order to maintain the wet state of the solid polymer electrolyte membrane constituting the fuel cell. As a system for solving such a problem, there is a fuel cell system described in JP-A-2000-208157.

Referring to FIG. 6, the fuel cell 51 is supplied with pure water from a water tank 52 through a pipe 53 by the operation of a pump 54. The cooling water that has cooled the fuel cell is discharged from the fuel cell 51, cooled by a heat exchanger 55 such as a radiator, and then collected in a water tank 52.

In the middle of the pipe 53, there is provided an ion removal filter 56 containing an ion exchange resin for removing conductive ions in the cooling water.

[0007]

However, when a predetermined amount of ions is adsorbed on the ion-exchange resin, the ion-removal filter 56 has a reduced ion-removing ability. Therefore, the ion-exchange resin is periodically replaced or maintenance is performed. Needed.

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

[0009]

According to a first aspect of the present invention, there is provided a fuel cell system including a fuel cell and a filter for removing impurity ions in cooling water supplied to the fuel cell.
As an ion removal filter, an electrochemical filter including an electrode on the cooling water phase side and an adsorption phase side electrode having an ion adsorption phase is used.

In a second aspect based on the first aspect, a plurality of the ion removal filters are arranged in series.

[0011] In a third aspect based on the first aspect, a plurality of the ion removal filters are arranged in parallel.

In a fourth aspect based on the second or third aspect, the potential difference applied to the ion removal filter is made different.

In a fifth aspect based on any one of the second to fourth aspects, the direction of the potential difference applied to the ion removal filter is changed.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects, means for detecting the conductivity of the cooling water, and a path provided downstream of the ion removal filter for discharging the cooling water to the outside. A control valve for switching to a path for supplying the fuel to the fuel cell; and control means for controlling switching of the control valve based on the conductivity detected by the conductivity detection means.

In a seventh aspect based on the sixth aspect, the control means reverses the direction of the potential difference of the ion removal filter when the conductivity of the cooling water reaches a predetermined value, and sends the cooling water to the outside. Switch control valve to discharge.

In an eighth aspect based on any one of the first to seventh aspects, a potential difference applied to the ion removal filter is supplied from a fuel cell.

[0017]

According to the first aspect of the invention, in the fuel cell system, the ion removal filter of the electrochemical filter including the cooling water phase side electrode and the adsorption phase side electrode having the ion adsorption phase is used. Impurity ions can be adsorbed to and removed from the ion-adsorbed phase from cooling water only when a potential difference is applied, and by inverting the polarity of each electrode, the impurity ions adsorbed on the ion-adsorbed phase can be released. Therefore, the ion removal capability can be maintained without replacing the ion removal filter or performing maintenance.

In the second aspect, since a plurality of ion removal filters are arranged in series, impurity ions in the cooling water can be efficiently removed.

In the third aspect, since a plurality of ion removal filters are arranged in parallel, the pressure loss in the ion removal filters can be reduced.

In the fourth aspect, since the potential difference applied to the ion removal filter is made different, the type of impurity ions to be removed can be selected by controlling the potential difference applied to the ion removal filter. Specifically, as the potential difference is larger, impurity ions having higher hydrophilicity can be taken in and concentrated by the ion-adsorbed phase, and when the potential difference is smaller, impurity ions having lower hydrophilicity can be removed.

In the fifth aspect, since the direction of the potential difference applied to the ion removal filter is made different, impurity cations and anions in the cooling water can be removed at the same time.

According to the sixth and seventh aspects of the invention, the conductivity detecting means for the cooling water, the control valve provided downstream of the ion removal filter and switching between a path for discharging the cooling water to the outside and a path for supplying the fuel cell to the fuel cell are provided. Based on the detected conductivity, when the conductivity of the cooling water reaches a predetermined value, the direction of the potential difference of the ion removal filter is reversed, and the control valve is switched so as to discharge the cooling water to the outside. Since the control is performed, maintenance-free operation of the ion removal filter can be realized.

According to the eighth aspect, the potential difference applied to the ion removal filter can be supplied without newly installing a power supply for the ion removal filter.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an ion removing filter according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 illustrates an ion removal filter according to a first embodiment of the present invention, in which an aqueous phase electrode 2 and an ion adsorption phase 3 are fixed between two insulating blocks 1. The aqueous phase side electrode 2 is sandwiched between the adsorption phase side electrode 4
The cooling water of the fuel cell is caused to flow between the fuel cell and the ion adsorption phase 3.

The ion-adsorbed phase 3 fixed to the electrode 4 on the adsorbed phase adsorbs and removes impurity ions in the cooling water by applying a potential difference between the electrodes. Polyvinyl chloride (PVC) in a solvent that does not dissolve in clean water
And the like to form a gel.

For example, when a potential difference is applied so that the aqueous phase side electrode 2 becomes + and the adsorption phase side electrode 4 becomes-, the impurity cations in the cooling water form an interface between the cooling water and the ion adsorption phase 3 from the cooling water. It passes and is adsorbed on the ion adsorption layer 3.

Therefore, the impurity ions are removed from the cooling water only when the potential difference is applied between the electrodes.
Can be adsorbed and removed. In addition, by reversing the polarity of each electrode, it is possible to release the impurity ions adsorbed on the ion-adsorbed phase 3 and to adsorb ions having the opposite sign to the released ions on the ion-adsorbed layer 3. . That is, the ion removal of the present invention is an electrochemical type ion removal filter.

FIG. 2 shows a configuration using the ion removal filter of the present invention in a fuel cell system. A plurality of ion removal filters 6 and 7 are provided in a cooling water path branched from a cooling water circulation path 5 for cooling the fuel cell. A water discharge valve 8 is disposed downstream of the ion removal filter 7 to control supply of cooling water to the cooling water circulation path 5 and discharge of the cooling water to the outside. The water discharge valve 8 discharges the cooling water to the outside according to the conductivity of the cooling water detected by the conductivity sensor 9 installed upstream of the ion removal filter 6, for example, when the conductivity is a predetermined value or more. Opened for. The conductivity sensor 9 for detecting the conductivity of the cooling water may be any means as long as it can detect the conductivity of the cooling water.
Further, the ion removal filter does not necessarily have to be provided branching from the cooling water circulation path 5, and may be provided directly in the cooling water circulation path 5.

At this time, the application of the potential difference may be performed by connecting the ion removing filters 6 and 7 in series as shown by the broken line in the figure or by connecting them in parallel.

Here, the type of impurity ions to be removed can be selected by controlling the potential difference applied to the ion removal filters 6 and 7. Specifically, the larger the potential difference,
The ion adsorption phase 3 can take in impurity ions having higher hydrophilicity and concentrate them. When a plurality of ion removal filters are arranged in series as in the present embodiment, for example, a small potential difference is applied to the ion removal filter 6 on the upstream side to take in the weakly hydrophilic impurity ions, and the ion removal filter on the downstream side is removed. By applying a large potential difference to the filter 7 to take in highly hydrophilic impurity ions, the impurity ions in the cooling water can be adsorbed on the adsorption layer 3. Therefore, impurity ions in the cooling water can be efficiently removed. At this time, the size of the ion removal filter may be different between the upstream side and the downstream side.

In the configuration of the second embodiment shown in FIG. 3, a plurality of ion removal filters 11 and 12 are arranged in parallel in a cooling water path branched from a cooling water circulation path 10 for cooling the fuel cell. A water discharge valve 13 is arranged downstream of 12 to control supply of cooling water to the cooling water circulation path 10 and discharge of cooling water to the outside. The water discharge valve 13 sends the cooling water to the outside according to the conductivity of the cooling water detected by the conductivity sensor 14 installed upstream of the ion removal filters 11 and 12, for example, when the conductivity is a predetermined value or more. Opened for discharge.

At this time, the application of the potential difference may be performed by connecting the ion removing filters 11 and 12 in series as shown by the broken line in the figure or by connecting them in parallel.

With such a configuration, the pressure loss in the ion removal filters 11 and 12 can be reduced.
Further, the type of impurity ions to be removed can be selected by controlling the potential difference applied to the ion removal filters 11 and 12. Specifically, as the potential difference is larger, the ion adsorption phase 3 can take in the more hydrophilic impurity ions and concentrate them. When a plurality of ion removal filters are arranged in parallel as in the present embodiment, for example, a small potential difference is applied to the ion removal filter 11 on the low potential side to take in impurity ions having weak hydrophilicity, and the ion removal filter 11 on the high potential side is taken in. By applying a large potential difference to the ion removal filter 12 to take in impurity ions having high hydrophilicity, the impurity ions in the cooling water can be adsorbed on the adsorption layer 3. At this time, the size of the ion removal filters 11 and 12 may be different between the high potential side and the low potential side.

Further, as shown by the solid lines in the first and second embodiments, by setting the potential difference of the plurality of ion removal filters to a positive potential difference and a reverse potential difference, both impurity cations and impurity anions can be removed simultaneously. Can be.

The third embodiment shown in FIG. 4 is different from the first or second embodiment in that a potential difference adjuster 15 and a controller 16 for controlling the adjuster are provided in the ion removal filter. . In the figure, one ion removal filter 6 is used.
Although only the configuration is shown, a plurality of ion removal filters of the present embodiment may be arranged in series or in parallel as in the configurations of FIGS.

With this configuration, the controller 16 determines the ion removal / adsorption capacity of the ion removal filter 6 based on the conductivity in the cooling water detected by the conductivity sensor 9, and discharges water when the conductivity of the cooling water reaches a reference value. By controlling or controlling the potential difference adjuster 15 provided in the valve 8 and the ion removing filter 6 to cut or reverse the potential difference applied to the ion removing filter 6, the impurity ions taken into the ion removing filter 6 and condensed are removed by a water discharge valve. 8 can be opened and discharged to the outside together with the cooling water. Therefore, there is no need to replace or regenerate the ion removal filter 6, and maintenance can be simplified.

In the fourth embodiment shown in FIG. 5, a potential difference is supplied from the fuel cell stack 17 as a power supply for supplying a potential difference of the ion removal filter 6. Here, by installing the polarity control unit 18 for controlling the polarity and the magnitude of the potential difference between the ion removal filter 6 and the fuel cell stack 17, there is no need to install another control device.

With this configuration, it is not necessary to provide a power supply necessary for the ion removal filter, and even if a potential difference is supplied from one of the cells of the plurality of fuel cell stacks to the ion removal filter, cooling is usually performed. Since the purity in water is adjusted to an appropriate range, almost no current flows through the ion removal filter 6, so that the voltage of the cell does not become lower than other cells. Therefore, the efficiency of the fuel cell system can be improved.

The present invention is not limited to the above-described embodiment, and it is apparent that various modifications can be made within the technical idea of the present invention.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an ion removal filter of the present invention.

FIG. 2 is a configuration diagram in which an ion removal filter is installed in the fuel cell system according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram in which an ion removal filter is installed in a fuel cell system according to a second embodiment.

FIG. 4 is a configuration diagram in which an ion removal filter is installed in a fuel cell system according to a third embodiment.

FIG. 5 is a configuration diagram in which an ion removal filter is installed in a fuel cell system according to a fourth embodiment.

FIG. 6 is a diagram illustrating a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulation block 2 Water phase side electrode 3 Ion adsorption phase 4 Adsorption phase side electrode 5 Cooling water circulation path 6 Ion removal filter 7 Ion removal filter 8 Control valve 9 Conductivity sensor

Claims (8)

[Claims] 1. A fuel cell system comprising: a fuel cell; and a filter for removing impurity ions in cooling water supplied to the fuel cell, wherein the adsorption water filter comprises an electrode on a cooling water phase side and an ion adsorption phase. A fuel cell system using an electrochemical filter comprising a phase-side electrode. 2. The steam reforming reactor according to claim 1, wherein a plurality of said ion removing filters are arranged in series. 3. The steam reforming reactor according to claim 1, wherein a plurality of said ion removal filters are arranged in parallel. 4. The steam reforming reactor according to claim 2, wherein a potential difference applied to the ion removal filter is made different. 5. The steam reforming reactor according to claim 2, wherein the direction of the potential difference applied to the ion removal filter is made different. 6. A means for detecting the conductivity of cooling water, a control valve provided downstream of the ion removal filter and configured to switch between a path for discharging cooling water to the outside and a path for supplying cooling fuel to the fuel cell; 2. A control means for controlling a direction of a potential difference of an ion removal filter and switching of said control valve based on the conductivity detected by said rate detection means.
6. The fuel cell system according to any one of claims 1 to 5. 7. The control means switches the control valve to reverse the direction of the potential difference of the ion removal filter when the conductivity of the cooling water reaches a predetermined value and to discharge the cooling water to the outside. The fuel cell system according to claim 6, wherein: 8. The fuel cell system according to claim 1, wherein a potential difference applied to the ion removal filter is supplied from a fuel cell.