JP2014107259A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a purification technique of air being supplied to a cathode electrode, or the like, in a fuel cell system.SOLUTION: Water (steam) produced by a cathode electrode 5b is condensed and separated in a heat exchanger 2c, and introduced to a drain tank 2a. Moisture in gas from an anode electrode 5a is condensed and separated in a heat exchanger 6c, and introduced to a drain tank 6a thence introduced to the drain tank 2a via piping L61. A part of water stored in the drain tank 2a is supplied to a drain tank 3a via piping L23. Dust is removed by a dust filter 3b from supply air before flowing into the drain tank 3a, and water soluble chemical substances in the air are removed through contact with water by bubbling when the air flows into the tank. The air thus cleaned is supplied to the cathode electrode 5b, a PROX catalyst layer 4c and, as bleeding air, to the anode electrode 5a.

Description

  The present invention relates to a fuel cell system, and more particularly to a technology for purifying air supplied to a cathode electrode or the like.

  Referring to FIG. 7, the conventional polymer electrolyte fuel cell system has a power generation system 101, a fuel processing system 102, a drain water recovery system 103, and a supply air purification system 104 as main components. The water generated or condensed and separated in the power generation system 101 is led to the drain water recovery system 103 through the pipes L101 and L102, purified by the ion exchange resin 105, and the stack cooling of the power generation system 101 through the pipes L104 and L105, and the fuel Supplied for steam reforming of the treatment system 102.

In the supply air purification system 104, the air supplied to the power generation system 101 and the fuel processing system 102 via the pipes L106 to L108 is purified by the purification dust filter 104a and the chemical adsorption filter (chemical filter) 104b.
The fuel cell stack is easily affected by chemical substances (SOx, NOx, NH3, etc.) in the supply air, and performance and durability are deteriorated even at a concentration level included in normal air. For this reason, it is common to mount a chemical adsorption filter (chemical filter) in the supply air path.

  However, if a filter that guarantees the equipment life of about 10 years required for a stationary system is installed, the filter volume that occupies the housing space becomes very large, so in the current product, the filter is regularly (every few years). Operation to exchange is made. This contributes to raising the total cost of the fuel cell system including maintenance.

  In addition, as a technique related to the air filter of the fuel cell system, a method (for example, Patent Document 1) in which dust is separated by vibration of an air prower, a method in which the package surface is an air filter (for example, Patent Document 2), and the like have been proposed. However, none has been put to practical use because of insufficient filter performance and package strength. In addition, these relate to technologies for removing dust in the air, and not for removing chemical substances (SOX, NOX, NH3, etc.).

JP 2012-84241 A Japanese Patent Laid-Open No. 2005-100722

On the other hand, for air purification other than fuel cell systems, a dripping or spraying type air washer system that uses pure water for water-soluble chemical substances (a system that removes chemical substances in the air by contacting with pure water) There is an example which adopts.
However, it is necessary to procure high-purity water from the outside, which complicates the system configuration and increases costs.
In view of the above problems, the present invention provides a fuel cell system provided with air purification means that does not require a chemical filter.

The gist of the present invention is as follows. That is, the fuel cell system according to the present invention is
(1) In a fuel cell system including a cell stack and a fuel processing device,
A drain recovery device for recovering drain water obtained at the cathode and anode of the cell stack;
A supply air purification device that removes impurities in the supply air using the drain water discharged from the drain recovery device;
Purified air supply means for supplying the air from which impurities have been removed by the supply air purification device to the cathode electrode of the cell stack;
It is characterized by comprising.

(2) In the invention of (1), the supply air purification device is characterized by comprising means for removing impurities in the supply air by a bubbling method.

(3) In the invention of (1), the supply air purifying device is characterized by comprising means for removing impurities in the supply air by a dropping type air washer system.

(4) In the invention of the above (1), the supply air purification device is provided with means for removing impurities in the supply air by a spray-type air washer system.

(5) In each of the above inventions, a water treatment device is further provided for removing impurities in the drain water from the recovered drain recovery device.

(6) In the above invention, the water treatment device is a water treatment device using an ion exchange resin.

(7) In each of the above inventions, the fuel cell system is a polymer electrolyte fuel cell system.

(8) In the above invention, the purified air supply means further supplies air from which impurities have been removed to the PROX catalyst layer of the fuel processor.

(9) In the above invention, the purified air supply means further supplies air from which impurities have been removed as bleed air between the fuel processing device and the cell stack.

  In general, in a fuel cell system, drain water generated in the reaction process is removed because sulfur-based impurities in the raw material gas have been removed, or a material with low elution is used for piping or the like (in the case of PEFC). Since it has a relatively high purity (generally, 10 μS / cm or less), it can be used for removing impurities in the air.

  According to the present invention, since the drain water that has been discarded as surplus in the past is used for removing impurities from the supply air, it is not necessary to periodically replace the chemical filter that is conventionally required. Costs and maintenance costs can be reduced. In particular, it is effective in reducing the cost of a polymer electrolyte fuel cell system in which chemical substances in the air are problematic because the operating temperature is low.

It is a figure which shows the system | strain block structure of the polymer electrolyte fuel cell (PEFC) system 1 which concerns on 1st embodiment. 1 is a diagram illustrating an overall configuration of a PEFC system 1. FIG. 1 is a diagram showing a fuel processing system A and a power generation system B of a PEFC system 1. FIG. It is a figure which similarly shows the drain collection system | strain C1. It is a figure showing drain supply systems C2 and C3 similarly. It is a figure which similarly shows the air purification / supply system D (D1, D2). It is a figure which shows the structure of the air purification apparatus 20 which concerns on 2nd embodiment. It is a figure which shows the structure of the air purification apparatus 30 which concerns on 3rd embodiment. It is a figure which shows the structure of the drain collection | recovery and supply system | strain C40 which concerns on 4th embodiment. It is a figure which shows the structure of the deformation | transformation aspect C40 'of the drain collection | recovery and supply system | strain C40. It is a figure which shows the same relationship in the conventional steam reforming system.

  Hereinafter, each embodiment of the present invention will be described in more detail with reference to FIGS. In each figure, the same components are denoted by the same reference numerals, and redundant description is omitted. Needless to say, the scope of the present invention is described in the claims and is not limited to the following embodiments.

(First embodiment)
<Overall configuration>
Referring to FIG. 1, a polymer electrolyte fuel cell (PEFC) system 1 (hereinafter abbreviated as “fuel cell system 1” as appropriate) according to an embodiment of the present invention is a fuel processing system for reforming a raw material gas. A, a power generation system B that extracts electric power by an electrochemical reaction of reformed gas and oxygen in the air, a drain recovery / supply system C that recovers water (drain) generated by the reaction and supplies it again to the system, It consists of an air purification / supply system D that purifies the air (oxygen) supplied to the system using water from the drain water recovery / supply system C, and a group of pipes that connect between the systems and each element in the system. ing.

FIG. 2 shows a detailed configuration of each system of the fuel cell system 1, and FIGS. 3A to 3D are diagrams showing divisions by system in the overall configuration.
<Fuel treatment system A>
Referring to FIG. 3A, the fuel processing system A includes a desulfurizer 4e that removes sulfur components in the raw material gas, a steam reforming catalyst layer 4a that reforms the raw material gas into a target gas composition, and a shift catalyst layer. 4b and a PROX catalyst layer 4c, and a fuel processing device 4 including a combustion burner 4d for supplying heat for the steam reforming reaction.
The reforming catalyst layer 4a is filled with a catalyst for steam reforming the source gas, for example, a Ru-based metal catalyst. The shift catalyst layer 4b is filled with a platinum catalyst or the like, and CO gas contained in the reformed gas is converted to CO ₂ by a shift reaction (2). The PROX catalyst layer 4c is filled with a selective CO removal catalyst such as Ru, and the CO concentration in the reformed gas is reduced to 10 ppm or less by the selective oxidation reaction (3).

The raw material gas (city gas) containing CH4 as a main component that has passed through the desulfurizer 4e is mixed with water (steam) in the reforming catalyst layer 4a, and then the gas containing hydrogen as a main component by the reforming reaction (1). To be modified. The reforming catalyst layer 4a is filled with a Ru-based metal catalyst or the like. Further, recovered water from a drain recovery / supply system C described later is used as the supply steam.
CH ₄ + H 2 O → CO + 3H ₂ (1)

The CO gas contained in the reformed gas is converted into CO ₂ by the shift reaction (2) in the shift catalyst layer 4b.
CO + H ₂ O → CO ₂ + H ₂ (2)
In the gas coming out of the shift catalyst layer 4b, the CO concentration in the gas is lowered to 10 ppm or less by the selective oxidation reaction (3) in the PROX catalyst layer 4c. As the air (oxygen) used in the reaction (3), air from an air purification / supply system D described later is used.
2CO + O ₂ → CO ₂ (3)

<Power generation system B>
In the power generation system B, a plurality of single cells each having an anode electrode (fuel electrode) 5a and a cathode electrode (air electrode) 5b arranged through a hydrogen ion permeable polymer electrolyte 5c are partitioned by a separator (not shown). A stacked cell stack (hereinafter abbreviated as a stack as appropriate) 5 is used. In the figure, only the single cell portion is displayed for convenience.

In the stack 5, the reformed gas discharged from the fuel processing device 4 is added with bleed air via a pipe L14 and guided to the anode 5a. Note that air from an air purification system D described later is used as bleed air for lowering the residual CO concentration.
An electrochemical reaction (4) is performed at the anode 5a, and the generated hydrogen ions (H ⁺ ) move inside the electrolyte 5c. In the cathode 5b, an electrochemical reaction (5) is performed. An electric current is taken out by the movement of the electrons (e ⁻ ) emitted by the reaction (5) through the external wiring connecting both electrodes.
2H2 → 4H ⁺ + 4e ⁻ (4)
O2 + 4e ⁻ + 4H ⁺ → 2H2O (5)

<Drain collection / supply system C>
3 (b) and 3 (c), a drain recovery / supply system C includes a drain recovery system C1 that recovers water generated in the system, and a fuel processor 4 and a stack 5 that collect the recovered water. And a supply system C3 for supplying the recovered water to the air purification device 3 of the air purification / supply system D.

  With reference to FIG.3 (b), the drain collection | recovery system | strain C1 is equipped with the drain tank 2a and the heat exchanger 2c, and the drain collection | recovery apparatus 2 which collect | recovers the water (drain) generated with reaction (5) in the cathode 5b. And a drain recovery device 6 that includes a drain tank 6a and a heat exchanger 6c and recovers water (drain) contained in the fuel off-gas from the anode 5a. Water level sensors 2b and 6b are respectively disposed inside the drain tanks 2a and 6, and are configured to be able to adjust the water level of the collected stored water within a certain range as will be described later.

  Referring to FIG. 3C, the drain supply system C2 includes a pipe L21 that connects the drain tank 2a and the fuel processing device 4, a pipe L22 that branches from the pipe L21 and reaches the stack 5, and a pipe L21 route. And a water treatment device 7 filled with an ion exchange resin to be interposed. The supply system C3 includes a pipe L23 that connects the drain tank 2a and the drain tank 3a of the air purification / supply system D, and an electromagnetic valve 2d that is interposed in the pipe L23 path.

  With the above configuration, in the drain water recovery / supply system C, water (steam) generated at the cathode electrode 5b is condensed and separated in the heat exchanger 2c and guided to the drain tank 2a. The exhaust gas after the condensation and separation is discharged to the outside through the exhaust port 8. On the other hand, moisture in the gas discharged from the anode electrode 5a is condensed and separated in the heat exchanger 6c, led to the drain tank 6a, and further led to the drain tank 2a via the pipe L61. The fuel off-gas containing the residual hydrogen after separation is sent to the combustion burner 4d and used for heating the reforming catalyst layer 4a.

A part of the water stored in the drain tank 2a passes through the water treatment device 7 and is processed to an electric conductivity equal to or lower than a predetermined reference value, and the reformed water supplied to the reforming catalyst layer 4a and the stack 5 Served as circulating water for cooling. The circulating water for cooling the stack 5 is recovered by exhaust heat in the heat exchanger 5d and stored as hot water in a hot water storage tank (not shown).
The remaining part is supplied to the drain tank 3a of the air purification / supply system D via the pipe L23. The water levels of the drain tanks 2a and 3a are adjusted by the water level sensors 2b and 3e, respectively, and the opening / closing control of the electromagnetic valves 2d, 3d, and 6d is performed so that the water levels of both tanks are within a certain range.

<Air purification / supply system D>
With reference to FIG.3 (d), the air purification | cleaning / supply system D is comprised by the purification system D1 and the supply system D2. The purification system D1 mainly includes an air purification device 3 including a dust filter 3b, an air blower 3c, a supply pipe L11, and a drain tank 3a for air purification.
The supply system D2 includes a pipe L12 that connects the air purification device 3 and the PROX catalyst layer 4c, a pipe L13 that connects the air purification device 3 and the cathode electrode 5b, and a gas pipe from the air purification device 3 and the PROX catalyst layer. It is comprised by piping L14 which connects L42.

  With the above configuration, in the air purification / supply system D, the air is taken into the drain tank 3a from the outside by the air blower 3c. At that time, dust in the air is removed by the dust filter 3b before entering the tank, and water-soluble chemical substances in the air are removed and brought into the system by contact with water by bubbling when flowing into the tank.

The purified air from which the chemical substances have been removed is supplied to the anode electrode 5a as the cathode electrode 5b, the PROX catalyst layer 4c, and the bleed air, and is used for the above-described reactions.
By the drain recovery and air purification flow described above, purification of supply air using recovered drain water is realized.

(Second embodiment)
Next, another embodiment of the present invention will be described. This embodiment is different from the first embodiment in the configuration of the air purification device. Referring to FIG. 4, the air purification device 3 of the first embodiment is a bubbling type air purification, whereas the air purification device 20 according to the present embodiment uses a dripping type air washer method. That is. For this reason, the dripping element 22 is provided inside the drain tank 3a. Further, in order to control the amount of drain dripping from the drain tank 2a to the dripping element 22, a pump 21 is provided in the communication pipe L23 path instead of the electromagnetic valve. Since the other configuration is the same as that of the fuel cell system 1, duplicate description is omitted.

  With the above configuration, in the air purification device 20, the air from which the dust has been removed by the dust filter 3 b is guided to the drain tank 3 a, and at that time, by contact with water that permeates the dropping element 22. Water-soluble chemicals are removed and taken into the system.

(Third embodiment)
Furthermore, another embodiment of the present invention will be described. The difference of this embodiment from the above-described embodiments is the configuration of the air purification device. Referring to FIG. 5, the air purification device 30 according to the present embodiment uses a spray-type air washer system. For this reason, the nozzle injection port 31 is provided in the air introduction part inside the drain tank 3a. Further, in order to control the nozzle injection amount, a pump 32 is provided in the communication pipe L23 path instead of the solenoid valve. Since the other configuration is the same as that of the fuel cell system 1, duplicate description is omitted.

  With the above configuration, in the air purification device 30, the air from which the dust has been removed by the dust filter 3b is guided to the drain tank 3a, and at that time, impurities are removed by contact with the drain water ejected from the nozzle ejection port 31. .

  In addition, according to the spray type or dripping type air washer system of the second and third embodiments, the pressure loss of the air supply path is reduced and the auxiliary machine power is reduced as compared with the bubbling system of the first embodiment. There are features such as being able to.

(Fourth embodiment)
Furthermore, another embodiment of the present invention will be described. This embodiment is different from the first embodiment in the configuration of the drain collection / supply system. That is, with reference to Fig.6 (a), the drain collection | recovery and supply system | strain C40 which concerns on this embodiment is provided with the water treatment apparatus 42 with which the path | route of the connection piping L41 was filled with ion exchange resin. Since the other configuration is the same as that of the fuel cell system 1, duplicate description is omitted.

With the above configuration, in this embodiment, since the water is supplied to the drain tank 3a after passing through the water treatment device 42, the purity of the water supplied to the cathode 5b and the like can be further increased.
This embodiment is effective when the purity of the drain water is low due to the influence of impurities in the source gas or when extremely high impurity removal is required.

  In addition, although the example which arrange | positions the water treatment apparatus 42 in the connection piping L41 path | route was shown in this embodiment, as shown in FIG.6 (b), the pipe L42 branched from the pipe L21 after passing the water treatment apparatus 7 is shown. It is also possible to provide the drain water after passing through the water treatment device 7 to the drain tank 3a. Thereby, there is an effect that it is not necessary to arrange a plurality of water treatment devices.

  The present invention is applicable not only to solid polymer fuel cell systems but also to fuel cell systems in general.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system 2, 6 ... Drain collection apparatus 2a, 3a, 6a ... Drain tank 2b, 3e, 6b ... Water level sensor 2c, 5d, 6c ... Heat exchanger 2d , 6d, 3d ... Solenoid valves 3, 20, 30 ... Air purification device 3b ... Dust filter 3c ... Air blower ... Fuel treatment device 4a ... Reforming catalyst layer 4b ... shift catalyst layer 4c ... PROX catalyst layer 4d ... combustion burner 4e ... desulfurizer 5 ... stack 5a ... anode electrode 5b ... cathode electrode 5c ... electrolyte 7, 42 ... Water treatment device 21, 32 ... Pump 22 ... Dropping element 31 ... Nozzle injection port A ... Fuel treatment system B ... Power generation system C, C40 ... Drain recovery / supply system D ... Air purification / supply system

Claims (9)

In a fuel cell system comprising a cell stack and a fuel processing device,
A drain recovery device for recovering drain water obtained at the cathode and anode of the cell stack;
A supply air purification device that removes impurities in the supply air using the drain water discharged from the drain recovery device;
Purified air supply means for supplying the air from which impurities have been removed by the supply air purification device to the cathode electrode of the cell stack;
A fuel cell system comprising:   2. The fuel cell system according to claim 1, wherein the supply air purification device includes means for removing impurities in the supply air by a bubbling method.   2. The fuel cell system according to claim 1, wherein the supply air purifying device includes means for removing impurities in the supply air by a dropping type air washer system.   2. The fuel cell system according to claim 1, wherein the supply air purification device includes means for removing impurities in the supply air by a spray-type air washer system.   The fuel cell system according to any one of claims 1 to 4, further comprising a water treatment device for removing impurities in the drain water discharged from the collected drain collection device.   The fuel cell system according to claim 5, wherein the water treatment device is a water treatment device using an ion exchange resin.   The fuel cell system according to any one of claims 1 to 6, wherein the fuel cell system is a polymer electrolyte fuel cell system.   8. The fuel cell system according to claim 7, wherein the purified air supply means further supplies air from which impurities have been removed to a PROX catalyst layer of the fuel processing apparatus. The fuel cell system according to claim 7 or 8, wherein the purified air supply means further supplies air from which impurities have been removed as bleed air between the fuel processing device and the cell stack.

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