JPH0695460B2 - Fuel cell - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a fuel cell in which a cell reaction temperature is cooled with water, and more particularly, to prolong the life of the cell and to eliminate the need for makeup water in the fuel cell plant. The present invention relates to a fuel cell capable of achieving the following.

[Technical background of the invention and its problems] In recent years, as a power generation device with few pollution factors and high energy conversion efficiency, the practical application of fuel cells has attracted great expectations, and the development of fuel cells by the public and private sectors has been strongly promoted. Is coming.

In this fuel cell, a pair of porous electrodes are usually arranged with a matrix impregnated with an electrolyte sandwiched between them, fuel such as hydrogen is brought into contact with the back surface of one electrode, and an oxidizer such as oxygen is attached to the back of the other electrode. And the electrochemical reaction that takes place at this time is used to extract electric energy from between the electrodes. Electric energy can be extracted with high conversion efficiency as long as the fuel and the oxidant are supplied. Is something that can be done.

FIG. 2 is a flow chart showing a system example of a hydrogen / oxygen fuel cell plant, which is currently most actively researched and developed.

In this figure, the fuel cell body 1 comprises a fuel electrode 2 and an oxidant electrode 3. Since the fuel cell body 1 takes away heat generated by the reaction of the fuel cell and controls the reaction temperature,
It is cooled by circulating cooling water. This cooling water system is provided with a cooling water circulation pump 4 and a cooling water steam separator 5. A part of the cooling water is sent to the water treatment device 7 through the raw water tank 6 to improve the water quality, and then sent to the fuel cell body 1 again.

Further, the reformed gas 12 is introduced into the fuel electrode 2 of the fuel cell body 1 as the fuel gas. Reformed gas that becomes this fuel gas
12 is obtained by the following reforming reaction and shift reaction. First, a hydrocarbon 9 such as natural gas and steam 10 are introduced into the reformer 8 as a raw fuel, and the reforming reaction represented by the following chemical reaction formula (the case of methane (CH ₄ ) is shown as an example) By carrying out, hydrogen is obtained.

CH ₄ + H ₂ O → 3H ₂ + CO Next, in the carbon monoxide shift converter 11, a shift reaction represented by the following chemical reaction formula is performed to further obtain hydrogen.

CO + H ₂ O → H ₂ + CO ₂ The steam 10 added excessively for such reforming reaction and shift reaction is reformed so that the humidity of the reformed gas 12 introduced into the fuel electrode 2 becomes optimum. The reformer condensed water 15 is separated from the reformed gas 12 in the device condenser 13 and the reformer steam-water separator 14.

On the other hand, air 16 is introduced into the oxidant electrode 3 as an oxidant gas. The reformed gas 12 and the air 16 react electrochemically,
It generates electricity and also water. The water produced is
It is discharged from the fuel cell body 1 as water vapor. Fuel pole 2
Further, a fuel electrode condenser 17, a fuel electrode steam / water separator 18, a oxidant electrode condenser 19, and an oxidant electrode / water separator 20 are provided downstream of the oxidizer electrode 3 and the oxidizer electrode 3. That is, the water generated in the fuel electrode 2 of the fuel cell body 1 is the water in the fuel electrode condenser 17
And it is separated from the reformed gas in the fuel electrode steam separator 18 and becomes the fuel electrode condensed water 21. Further, the water generated in the oxidant electrode 3 of the fuel cell main body 1 is separated from the reformed gas in the oxidant electrode condenser 19 and the oxidant electrode steam / water separator 20 to become the oxidant electrode condensed water 22.

Further, the fuel electrode outlet gas 23 serves as fuel for a burner (not shown) that supplies heat necessary for the reforming reaction in the reformer 8. Further, the oxidant electrode outlet gas 24 is introduced into a turbine of a turbo compressor (not shown) and power is recovered. 25
Is raw water supplied as plant makeup water.

By the way, as a cooling method of a fuel cell, there are a water cooling method and an air cooling method. FIG. 2 shows the case of the water cooling system. The water cooling system has a feature that the cooling water system is compact and the waste heat can be easily used, but has a problem peculiar to the fuel cell as described below.

First, if the water quality of the battery cooling water is low, electrolytic corrosion will clog the cooling pipes, making it impossible to generate electricity.
Water quality of ultrapure water level of cm or less and turbidity of 10PPB or less is required.

Secondly, since the reformer condensed water 15 contains an organic substance such as methanol, water treatment is required to collect it as battery cooling water.

Of these two problems, the first problem will be described below.

FIG. 3 is a perspective view showing a structural example of the fuel cell main body 1. In this figure, several fuel cells
A cooling plate 27 is inserted every 26. A thin cooling pipe 28 is embedded in the cooling plate 27. Further, since there is a potential difference between the cooling plates 27 due to the unit cells 26 stacked in series, they are electrically insulated by the insulating tube 29.

FIG. 4 is a cross-sectional view showing details around the insulating tube 29. Insulation joints 30a at both ends of the insulation tube 29,
Since there is a potential difference between 30b, electrolytic corrosion due to leak current occurs and the metal ions increase. And, in the cooling water, metal ions such as iron ions or copper ions
If the content is 10 PPB or more, the metal compound adheres to the small diameter portions at the ends of the insulating joints 30a and 30b, and clogging occurs due to the deposit 31. This clogging gradually progressed, and as a result,
The cooling water flow rate gradually decreases, and the battery is not cooled sufficiently. When the power generation is further continued, the battery temperature gradually rises, and eventually the battery temperature cannot be controlled. When the battery temperature rises, the battery catalyst deteriorates, the battery life is shortened due to the evaporation of the battery electrolyte, and the electrode burns out due to the crossover of fuel and air, making it impossible to generate electricity. Therefore, the battery cooling water is required to have a high water quality with an electric conductivity of 0.4 μ / cm and a turbidity of 10 PPB or less. However, because it is difficult to maintain such high water quality and maintain it for a long period of time,
In the past, shortening the life of fuel cells and reducing the reliability of power generation equipment have been unavoidable problems.

Next, the second problem will be described.

The total amount of the three types of condensed water, that is, the reformer condensed water 15, the fuel electrode condensed water 21, and the oxidant electrode condensed water 22, is larger than the amount of steam 10 required for the reforming reaction in FIG. This is because the hydrogen atom of methane becomes hydrogen gas in the reforming reaction and becomes water in the battery. Therefore, if the three types of condensed water are recovered and can be used as cell cooling water, the fuel cell plant does not need makeup water.

However, the three types of condensed water each have an electric conductivity of 5
~ 50μ / cm, turbidity is 5-150PPB, water treatment is required before using as battery cooling water. Also, the reforming tank condensed water
15 contains organic substances such as methanol. For example, in the case of methanol, formic acid (HCOOH) is generated by oxidation, which may corrode pipes and equipment, and water treatment is required before use as battery cooling water. .

FIG. 5 shows an outline of the battery cooling water system of the system shown in FIG. In this figure, raw water 25 such as river water and groundwater is stored in a raw water tank 6 and then treated by a water treatment device 7 such as filtration, coagulation sedimentation, ion exchange and decarbonation to become pure water, and the fuel cell main body 1 is supplied. A part of the cell cooling water is returned to the raw water tank 6 as a blowdown 32, the water quality is improved by the water treatment device 7, and then is supplied to the fuel cell main body 1 again.

Further, the reformer condensed water 15 obtained in the reformer steam-water separator 14 is the fuel electrode condensed water 21 and the oxidizer obtained in the fuel electrode steam-water separator 18 and the oxidant electrode steam-water separator 20. It merges with the polar condensed water 22 and is collected in the raw water tank 6.

After operating the same system, as a result of collecting and analyzing the above-mentioned three kinds of condensed water, the battery cooling water quality was determined to be 0.4 μ / conductivity.
It has been found that it is difficult to process to cm or less and turbidity of 10 PPB or less. Furthermore, it was also found that in order to maintain a certain level of performance, maintenance such as backwashing / replacement of the filtration device / activated carbon and regeneration of the ion exchange resin must be carried out frequently.

It should be noted that organic substances such as methanol cannot be removed by treatment methods such as filtration, coagulation and precipitation, ion exchange, and decarboxylation, and other treatment methods are required.

Therefore, in the conventional system, it is difficult to recover the condensed water as battery cooling water, and it is necessary to make up the battery cooling water, so that it is especially difficult to replenish the water in islands, deserts, mountains, and cities. It becomes difficult to locate in such places.

[Object of the Invention] The present invention has been proposed in order to solve the above problems, and an object thereof is to maintain high water quality of battery cooling water, prevent clogging of a battery cooling pipe, and improve fuel efficiency. The life of the battery is extended, the reliability of the power generation equipment is improved, the condensed water is recovered so that it can be used as the cooling water for the battery, and the fuel cell plant becomes a plant that does not require makeup water.
By providing a fuel cell that facilitates location in deserts, mountains, and cities, and can remove organic substances such as methanol contained in the condensed water of the reformer to prevent corrosion of pipes and equipment. is there.

[Summary of the Invention] In a fuel cell plant water treatment system of the present invention, primary and secondary water treatment devices are installed in series, raw water of low water quality,
After the fuel electrode condensed water and the oxidant electrode condensed water are subjected to the primary treatment with the primary water treatment device, the primary treatment water and the used cooling water (blow down) having high water quality are treated with the secondary water treatment device. The secondary processing is performed.

With such a configuration, since the secondary treatment device always treats only pure water, it is possible to always supply good quality cooling water to the fuel cell main body and prevent clogging of the cell cooling pipe. In addition, various kinds of condensed water can be used as battery cooling water.

Further, by introducing the condensed water of the reformer into the primary treatment device, the amount of condensed water to be reused as battery cooling water can be increased, and the amount of makeup water can be reduced accordingly. In particular, the reformer condensate water is separated from the other condensate water, and the organic matter treatment device is used to remove organic substances such as methanol, so that the water quality of the reformer condensate water is sufficiently improved before the primary It can be introduced into the processor and mixed with other condensed water and raw water. In this case, there is no risk of corroding the pipes and equipment by the organic substances such as methanol contained in the condensed water of the reformer.

[Embodiment of the Invention] An embodiment of the present invention as described above will be specifically described with reference to FIG.

FIG. 1 is a schematic flow chart of the battery cooling water system showing the present embodiment, and the same parts as those in FIGS. 2 and 5 are designated by the same reference numerals. Introduce raw water 25 as shown in this figure 1
The secondary water storage tank 33, the primary water treatment device 34, the secondary water storage tank 36, the secondary water treatment device 37, and the fuel cell main body 1 are connected in series in this order. In this case, the primary water treatment device 34 is a device that sequentially performs the processes of filtration, coagulation and precipitation, ion exchange, decarboxylation, and adsorption. In addition, the secondary water treatment device 37
Is an apparatus for sequentially performing filtration, adsorption ion exchange, and degassing. In addition, a part of the cell cooling water of the fuel cell body 1 is
The blowdown 32 is returned to the secondary water storage tank 36.

On the other hand, upstream of the primary water storage tank 33, a fuel electrode / water separator 18, an oxidizer electrode / water separator 20, and a reformer device / water separator 14 are connected. Each of the condensed waters 21, 22, 15 from the vessels 18, 20, 14 is introduced into the primary water storage tank 33, respectively. In this case, the fuel electrode / water separator 18 and the oxidant electrode / water separator 20 have the same system.
It is connected to the secondary water storage tank 33. On the other hand, the reformer steam-water separator 14 is connected to the primary storage tank 33 in a system different from the fuel electrode steam-water separator 18 and the oxidant electrode steam-water separator 20. An organic substance treatment device 38 that removes organic substances such as methanol using hydrogen peroxide and an ultraviolet irradiation device is provided between the reformer steam separator 14 and the primary water storage tank 33. .

The operation of this embodiment having the above configuration is as follows. First, the raw water 25 is stored in the primary water storage tank 33, and then undergoes filtration, coagulation and sedimentation, ion exchange, decarboxylation, and adsorption by the primary water treatment device 34 to become pure water 35. This pure water 35 is stored in the secondary water storage tank 36, and then filtered, adsorbed and ion-exchanged by the secondary water treatment device 37.
After being degassed, it becomes good quality cooling water. In addition, a part of the cooling water used for cooling the fuel cell body 1 is returned to the secondary water storage tank 36 as a blowdown 32, mixed with pure water 35, and filtered and adsorbed by the secondary water treatment device 37. After being subjected to ion exchange and degassing, it becomes good quality cooling water.

On the other hand, in the present embodiment, the fuel electrode condensed water 21 and the oxidant electrode condensed water 22 obtained by the fuel electrode steam water separator 18 and the oxidant electrode steam water separator 20 are combined to form a primary water storage tank. After being returned to 33, it is filtered with the raw water 25 by the primary water treatment device 34.
Pure water 35 is obtained by sequentially undergoing coagulation and precipitation, ion exchange, decarboxylation, and adsorption.

Further, in the present embodiment, the reformer condensed water 15 obtained by the reformer steam-water separator 14 is treated by the organic matter treatment device 38 separately from the fuel electrode condensed water 21 and the oxidant electrode condensed water 22. , Organic matter such as methanol is decomposed and removed,
Return to the primary water storage tank 33. After that, the condensate water 15 of the reformer is treated by the primary treatment device 34 together with the raw water 25, the fuel electrode condensate water 21, and the oxidant electrode condensate water 22 for filtration, coagulation sedimentation, ion exchange, decarboxylation, and adsorption treatment. Received pure water
35.

Therefore, according to this embodiment, the secondary water treatment device 37 is
Since only pure water 35 is always treated, the fuel cell body 1 always has good quality cooling water, that is, an electric conductivity of 0.4 μ / cm or less and a turbidity.
Cooling water of 10PPB or less can be supplied. Therefore, clogging of the cooling water pipe is prevented, the life of the fuel cell is extended, and long-term continuous power generation operation is possible, and the reliability of the power generation equipment can be improved. Since the purity of the treated water is increased, there is also an advantage that the frequency of maintenance such as backwashing / replacement of the filtration device / activated carbon and regeneration of the ion exchange resin can be reduced as compared with the conventional case.

Further, since the organic matter such as methanol in the reformer condensed water 15 is treated by the organic matter treatment device 38 and the three kinds of condensed water are treated by the primary water treatment device 34, it is sufficient as battery cooling water. Condensed water with high purity water quality can be recovered. As a result, the fuel cell plant becomes a closed system that does not require make-up water, making it easy to locate islands, deserts, mountains, cities, etc. where water supply is difficult.

In particular, in this embodiment, since the organic matter treatment device 38 is installed, even if drainage is performed, the biochemical oxygen demand (BOD) of the drainage is low and there is no risk of environmental pollution.

Further, since the secondary water treatment device 37 always treats only the pure water 35, there is also an advantage that the frequency of maintenance such as filter cleaning / replacement and ion exchange resin regeneration / replacement is low.

Further, by separating the condensed water line of the reformer from the other condensed water line, the capacity of the organic substance treatment device 38 such as methanol can be minimized, and the device can be downsized.

Incidentally, the present invention is not limited to the above examples, instead of the organic matter treatment device using hydrogen peroxide and ultraviolet irradiation device, activated sludge device, catalytic oxidation treatment device, sodium hypochlorite (NaClO ) And an organic substance treating apparatus using a nickel catalyst, it is possible to treat an organic substance such as methanol.

Further, the present invention is not necessarily limited to the above-mentioned configuration for recovering three types of condensed water, and for example, a configuration in which only the fuel electrode condensed water and the oxidant electrode condensed water are recovered and used as cooling water is also possible. Of course, in such a case, it is needless to say that a sufficient effect can be obtained without providing an organic matter treatment device for the condensed water of the reforming device.

[Effects of the Invention] As described above, according to the present invention, two water treatment devices are provided in series, raw water and various condensed water are treated upstream, and treated water and battery cooling water upstream are treated downstream. By configuring it for treatment, the quality of the battery cooling water is maintained high, the life of the fuel cell is extended, the reliability of the power generation equipment is improved, and the condensed water is recovered so that it can be used as battery cooling water. The fuel cell plant is made into a plant that does not require makeup water, facilitating the location in islands, deserts, mountainous areas, and cities where it is difficult to replenish water, and it is also possible to remove organic substances such as methanol contained in the condensed water of the reformer. It is possible to provide an excellent fuel cell that can prevent corrosion of piping and equipment.

[Brief description of drawings]

FIG. 1 is a flow chart of a cell cooling water system showing an embodiment of the present invention, FIG. 2 is a flow chart of a fuel cell plant, FIG. 3 is a perspective view showing a configuration example of a fuel cell main body, and FIG. Is a cross-sectional view showing details of the periphery of an insulating tube of a cooling water system, and FIG. 5 is a flow chart of the battery cooling water system of FIG. 1 ... Fuel cell main body, 2 ... Fuel electrode, 3 ... Oxidizer electrode,
4 ... Cooling water circulation pump, 5 ... Cooling water / water separator, 6
…… Raw water tank, 7 …… Water treatment device, 8 …… Reformer, 9
... hydrocarbons such as natural gas, 10 ... steam, 11 ... carbon monoxide shifter, 12 ... reformed gas, 13 ... reformer condenser, 14 ... reformer gas-water separator, 15 …… Reformer condensate, 16 …… Air, 17 …… Fuel electrode condenser, 18 …… Fuel electrode steam separator, 19 …… Oxidizer electrode condenser, 20 …… Oxidizer electrode steam separation Vessel, 21 ... Fuel electrode condensed water, 22 ... Oxidizer electrode condensed water,
23 …… Fuel electrode outlet gas, 24 …… Oxidizer electrode outlet gas, 25…
… Raw water, 26 …… Single cell, 27 …… Cooling plate, 28 …… Cooling pipe,
29 …… Insulation tube, 30 …… Insulation joint, 31 …… Adhesion,
32 …… Blowdown, 33 …… Primary water storage tank, 34 ……
Primary water treatment equipment, 35 ... Pure water, 36 ... Secondary water storage tank, 37 ... Secondary water treatment equipment, 38 ... Organic matter treatment equipment.

Claims (3)

[Claims] 1. A fuel cell main body comprising a fuel electrode for introducing a fuel gas and an oxidant electrode for introducing an oxidant gas, the fuel cell main body producing electricity and water by an electrochemical reaction between the fuel gas and the oxidant gas, and A fuel electrode water-water separator for separating the water produced at the fuel electrode of the fuel cell body from the fuel gas to obtain fuel electrode condensed water; and the water produced at the oxidizer electrode of the fuel cell body as an oxidizer. In a fuel cell including an oxidizer electrode-water separator that separates from gas to obtain oxidizer electrode condensed water, and a cooling water system that circulates cooling water in the fuel cell body to cool the cooling water system, The raw water to be replenished to the fuel electrode, the fuel electrode condensed water obtained by the fuel electrode water vapor separator, and the oxidant electrode condensed water obtained by the oxidant electrode water vapor separator are introduced to perform the primary treatment. A primary water treatment device to be provided, and a primary water treatment device provided in series downstream of the primary water treatment device. A secondary water treatment device that introduces water after the primary treatment by the primary water treatment device and used cooling water of the cooling water system to perform a secondary treatment different from the primary treatment. The fuel cell is characterized in that the cooling water system is configured to supply the water after the secondary treatment by the secondary water treatment device as cooling water into the fuel cell main body. 2. A reformer for reforming raw fuel with steam to generate reformed gas and supplying the reformed gas as fuel gas to the fuel cell main body, and a reformer generated by the reformer. A reformer steam-water separator that separates water from a quality gas to obtain a reformer condensed water, wherein the primary water treatment device is obtained by the reformer steam-water separator The fuel cell according to claim 1, wherein the fuel cell is configured to further introduce condensed water to perform the primary treatment. 3. An organic matter treatment device for performing treatment for removing organic matter of the reformer condensed water obtained by the reformer steam water separator, wherein the primary water treatment device is the organic matter treatment device. The fuel cell according to claim 2, wherein the fuel cell is configured to introduce the reformer condensed water after being treated.