JP3349801B2 - Nitrogen circulator in fuel cell power generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for circulating nitrogen gas for use in sealing a fuel cell body or purging the inside of the apparatus in a fuel cell power generator.

[0002]

2. Description of the Related Art FIG. 7 shows an example of a conventional power generator using a fuel cell. The gas flow in this device is mainly divided into a fuel gas system and an air system.

A) Fuel gas system First, raw fuel gas (natural gas) is introduced into a reformer 18 from a pump 10 through a heat exchanger 12, a desulfurization reactor 14, and a heat exchanger 16 in that order. The gas is converted into a reformed gas by heating by a burner provided in the reformer 18. The reformed gas is supplied to the heat exchanger 16, the heat exchanger 20, the high-temperature CO converter 22, the heat exchanger 12, the heat exchanger 24, the low-temperature CO converter 26, the heat exchanger 28, and the waste heat recovery heat exchange. The fuel gas and water separator 32 is introduced into the fuel gas / water separator 32 through the device 30 in order. The water separated by the steam separator 32 is introduced into a water treatment device 34, and a part of the gas is returned to the natural gas side by a circulation blower 36. The remaining gas is supplied to the fuel electrode 40A of each fuel cell 38 through the heat exchanger 28, and reacts in the fuel cell 38 to generate electric power. The gas after the reaction is led out from the fuel electrode 40A as fuel discharged from the cell, and supplied to the burner of the reformer 18 through the passage 41A.

B) Air system In this system, the raw material air passes through a compressor 52, a cooler 54, and a compressor 56 in this order, and an air electrode 40 of each fuel cell 38 is provided.
B, the oxygen in the air is consumed in the combustion of the fuel, and the remaining gas becomes exhaust gas (anode exhaust gas) of the cell rich in nitrogen gas. This battery exhaust air is supplied to the passage 41.
B, and sent to the burner of the reformer 18 through the heat exchangers 20 and 42.

The combustion gas generated in the reformer 18 is supplied to the heat exchanger 42, turbine 44, heat exchanger 46,
Then, the water is sent to the exhaust gas / water separator 50 through the cooler 48 in order, and the separated water is sent to the water treatment device 34, while the gas is discharged out of the system through the exhaust pipe 52.

By the way, in such a power generator, a large amount of nitrogen gas is consumed for sealing inside and outside the fuel cell main body, boosting pressure, purging, and the like. For example, during normal operation,
As shown in FIG. 8A, a small amount of nitrogen gas is constantly consumed to seal the fuel cell body from the outside. When the device is started, as shown in FIG.
After nitrogen gas is used to increase the pressure of the reforming system, nitrogen gas is used again to increase the pressure of the fuel cell after a heating time. Further, when the apparatus is stopped, as shown in FIG.
Nitrogen gas is used for purging the reforming system.

Therefore, conventionally, a liquid nitrogen tank truck 58 and a nitrogen storage device 60 are installed as shown in FIG. 7 to supply the nitrogen gas to the power generation device. It is common practice to distribute nitrogen gas to locations using nitrogen.

[0008]

As described above, conventionally, a relatively large amount of relatively expensive nitrogen gas is supplied from the outside of the apparatus to the inside of the apparatus, and this greatly hinders the reduction of the power generation cost. ing.

In view of such circumstances, an object of the present invention is to provide a fuel cell-based power generation apparatus capable of inexpensively obtaining nitrogen gas for cell sealing and purging.

[0010]

As a means for solving the above-mentioned problems, the present invention provides an oxygen separator for separating oxygen gas from a supplied gas, and an oxygen separator separated and purified by the oxygen separator. An oxygen supply passage leading to the oxygen electrode,
A nitrogen separator for separating nitrogen gas from the supplied gas, a nitrogen-rich gas transfer passage for supplying the remaining nitrogen-rich gas after separation of the oxygen gas in the oxygen separator to the nitrogen separator, A nitrogen supply passage for supplying nitrogen gas separated and purified by the nitrogen separation device to a place where nitrogen is used in the power generation device is provided (claim 1).

In this apparatus, an air supply passage for introducing the raw material air to the oxygen electrode together with the oxygen gas separated and purified by the oxygen separation device, and the raw material air introduced to the oxygen electrode through the air supply passage and the oxygen separation passage It is more preferable to include an oxygen concentration adjusting means for changing a ratio of oxygen gas introduced into the oxygen electrode from the device (claim 2).

Further, the present invention provides a nitrogen separator for separating nitrogen gas from a supplied gas, and a nitrogen-rich gas extraction passage for extracting nitrogen-rich gas derived from the oxygen electrode and introducing the same into the nitrogen separator. And a nitrogen supply passage for supplying the nitrogen gas separated and purified by the nitrogen separation device to a place where nitrogen is used in the power generation device.

[0013]

According to the above construction, the gas is taken out from the gas passage provided in the power generator, the nitrogen gas is separated and purified from the gas by the nitrogen separator, and the gas is supplied to the use place of the nitrogen gas. At least a part of the nitrogen gas required for the operation of the power generator is purified in the power generator.
That is, the nitrogen gas is circulated in the power generator, and the amount of the nitrogen gas that needs to be supplied from the outside can be reduced or set to zero accordingly. Moreover, since the gas is taken out from the portion where the gas having a higher nitrogen concentration than the air flows, the nitrogen recovery rate by the nitrogen separation device is higher than when the raw material air is directly taken into the nitrogen separation device.

Specifically, in the apparatus according to the first aspect, the nitrogen-rich gas after the oxygen gas is separated in the oxygen separation apparatus is transferred to the nitrogen separation apparatus, and the nitrogen gas separated and purified by the nitrogen separation apparatus. Is supplied to a nitrogen use point through a nitrogen supply passage. Further, since the oxygen gas separated and purified by the oxygen separator is led to the oxygen electrode of the fuel cell, the output of the fuel cell is increased as compared with the conventional case where the raw material air is directly introduced into the fuel electrode.

Further, in the apparatus according to the second aspect, the ratio between the raw material air introduced into the oxygen electrode through the air supply passage and the oxygen gas introduced into the oxygen electrode from the oxygen separator is adjusted by the oxygen concentration adjusting means. Thereby, the oxygen concentration in the oxygen-containing gas supplied to the oxygen electrode can be appropriately adjusted.

Further, in the apparatus according to the third aspect, the nitrogen-rich gas after the oxygen has been consumed at the oxygen electrode is introduced into a nitrogen separation apparatus, and the nitrogen gas separated and purified by the nitrogen separation apparatus is used at a nitrogen use site. Will be supplied.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. In this embodiment, the configuration of the entire power generator is the same as that shown in FIG. 7, and the description thereof is omitted here.

In the apparatus shown in this embodiment, as shown in FIG. 1, an air supply passage 68 for introducing raw air to the oxygen electrode 40B through an air filter 64 is provided. (Oxygen concentration adjusting means) 6
6 is provided, and an oxygen separator 70 for purifying and separating oxygen gas from the raw material air is provided. The oxygen gas separated and purified by the oxygen separating device 70 is mixed with the raw material air flowing through the air supply passage 68. They are merged and introduced into the oxygen electrode 40B. Further, the exhaust gas of the oxygen separator 70 (that is, the remaining nitrogen-rich gas after the oxygen gas is separated) is transferred to the nitrogen separator 74 through the nitrogen-rich gas transfer passage 72, and is separated and purified by the nitrogen separator 74. The introduced nitrogen gas is introduced into the seal portion 39 surrounding the main body of the fuel cell 38 through the passage 76 and the passage 62 shown in FIG. The seal portion 39 is provided to seal the fuel cell main body including the two electrodes 40A and 40B and the outside of the fuel cell 38. When the nitrogen gas is supplied into the seal portion 39, the seal portion 39 is sealed. Is configured to be performed.

The oxygen separator 70 and the nitrogen separator 7
FIG. 2 shows a specific configuration of No. 4. In this embodiment, the oxygen separator 70 is constituted by an oxygen PSA unit, and the nitrogen separator 74 is constituted by a nitrogen PSA unit.

The oxygen separating device 70 includes an air filter 7
8. Raw material air blower 80, three adsorption towers 82, adsorption valve upstream switching valve 84, adsorption tower downstream switching valve 86, exhaust gas blower 88, oxygen receiver 90, valve 92, oxygen gas compressor 94, cooling Vessel 96, oxygen gas holder 98, valve 10
0 and a separator 102. Each adsorption tower 82
Is filled with an adsorbent that preferentially adsorbs nitrogen, such as zeolite molecular sieve.

In this apparatus, in the adsorption step, each adsorption tower 8 is passed through an air filter 78 and a raw material air blower 80.
2, the nitrogen in the raw air is adsorbed by the adsorbent, and the remaining oxygen gas is supplied to the oxygen receiver 9.
0, a valve 92, an oxygen gas compressor 94, and a cooler 96 are stored in an oxygen gas holder 98. The oxygen gas in the oxygen gas holder 98 is discharged to the air supply passage 68 through the valve 100 as appropriate. On the other hand, the remaining nitrogen-rich gas is transferred as exhaust gas from the exhaust gas blower 88 and the separator 102 to the nitrogen separator 74 through the nitrogen-rich gas transfer passage 72.

The nitrogen separator 74 includes a nitrogen compressor 104,
An activated carbon tower 106, two adsorption towers 108, a switching valve 110 on the upstream side of the adsorption tower, a switching valve 112 on the downstream side of the adsorption tower, and a nitrogen gas tank 114 are provided. Each of the adsorption towers 108 includes, for example, a carbon molecular sieve such as a carbon molecular sieve. Is packed with an adsorbent that preferentially adsorbs.

In this apparatus, in the adsorption step, the nitrogen-rich gas introduced from the nitrogen-rich gas transfer passage 74 is passed through the nitrogen compressor 104 and the activated carbon tower 106 to the adsorption tower 108.
And the oxygen is adsorbed by the adsorbent, and the nitrogen gas is stored in the nitrogen gas tank 114. Then, the nitrogen gas in the nitrogen gas tank 114 is appropriately discharged into the passage 62 through the passage 76. In the desorption step, gas desorbed from the adsorbent is exhausted.

Next, the operation of this embodiment will be described.

The raw air is directly supplied to the oxygen electrode 40B through an air supply passage 68 having an air filter 64 and a flow control valve 66. In the oxygen separator 70, oxygen gas is purified and separated from the raw air. The purified oxygen gas is also supplied to the air supply passage 68 through the flow control valve 66.
The oxygen is supplied into the oxygen electrode 40B through a portion on the downstream side. Accordingly, a gas having a higher oxygen concentration than the source air is supplied to the oxygen electrode 40B, and the oxygen concentration in the oxygen-containing gas can be adjusted by operating the flow control valve 66. Specifically, the oxygen concentration of the supply gas is increased as the opening of the flow control valve 66 is reduced.

On the other hand, the exhaust gas from the oxygen separator 70, ie, the remaining nitrogen-rich gas after the oxygen gas is separated, is passed through the nitrogen-rich gas transfer passage 72 to the nitrogen separator 74.
The nitrogen gas is purified and separated by the nitrogen separator 74. This nitrogen gas passes through the passages 76 and 62 that constitute the nitrogen gas supply passage, and the sealing portion 39 of the fuel cell 38.
And supplied to the seal of the fuel cell body.

The combustion gas in the fuel electrode 40A and the combustion gas in the oxygen electrode 40B are supplied to the burner 19 of the reformer 18 through the passages 41A and 41B, respectively.

Therefore, according to this device, the following a),
The two effects b) can be obtained simultaneously.

A) Oxygen gas is separated and purified from the raw material air by the oxygen separator 70, and this oxygen gas is supplied to the oxygen electrode 40B together with the raw material air. Can be higher than
The output of the fuel cell 38 can be increased accordingly.

FIG. 3 is a graph showing the oxygen utilization rate and the output improvement rate corresponding to the oxygen concentration at the fuel cell inlet (the improvement rate as compared with the case where the raw material air is used as in the prior art). The oxygen utilization rate here is the ratio of the amount of oxygen consumed in combustion to the total amount of oxygen contained in the supply gas, and the lower the oxygen utilization rate, the more the oxygen concentration in the supply gas has a margin. It is shown that.

As is clear from this graph, the output of the fuel cell can be improved by increasing the oxygen concentration at the fuel cell inlet by using the oxygen separator 70.

Further, in this embodiment, since the flow rate control valve 66 is provided so that the oxygen concentration of the supplied gas can be adjusted, the oxygen concentration is reduced during a period when the power consumption is low (for example, at night). Thus, it is possible to save oxygen gas. However, in the present invention, such an oxygen concentration adjusting means may be omitted, and only the oxygen gas purified by the oxygen separator 70 may be supplied to the oxygen electrode 40B.

B) By extracting nitrogen-rich gas from the exhaust gas of the oxygen separator 70 and introducing it into a nitrogen separator 74, the nitrogen separator 74 purifies and separates the nitrogen gas.
The sealing nitrogen gas of the fuel cell 38 can be purified in the power generator. Therefore, the required amount of nitrogen gas that must be supplied from the outside (from the nitrogen storage device 60 in FIG. 1) is greatly reduced, and in some cases, the external supply can be completely omitted. Therefore, the necessary nitrogen gas can be obtained at very low cost, and the power generation cost can be reduced.

Further, since the nitrogen-rich gas, which is the exhaust gas of the nitrogen-oxygen separator 70, is supplied to the nitrogen separator 74, for example, the raw material air is supplied to the nitrogen separator 7.
4, the nitrogen gas recovery rate can be further increased.

FIG. 4 is a graph showing the relationship between the oxygen concentration of the gas sent to the nitrogen separator 74 and the nitrogen recovery rate. From this figure, the lower the oxygen concentration in the source gas,
That is, it can be understood that the higher the nitrogen concentration, the higher the nitrogen recovery rate. For example, raw material air (oxygen concentration about 21
%), A nitrogen recovery of only about 20% can be obtained, but if the oxygen concentration is reduced to 10%, the nitrogen recovery can be improved to about 50%. Therefore, as shown in this embodiment, by separating and purifying nitrogen gas using the nitrogen-rich gas from which oxygen has been removed by the oxygen separator 70, the nitrogen recovery rate can be greatly increased, and the nitrogen gas can be produced at lower cost. It is possible to obtain.

Next, a second embodiment will be described with reference to FIG. In this embodiment, a surplus of nitrogen gas purified by the nitrogen separator 74 is once injected into the nitrogen gas tank 120 through the valve 116 and the compressor 118, and the valve 122 is removed from the nitrogen gas tank 120 at an appropriate time thereafter. Nitrogen gas is supplied to the place where nitrogen is used.

According to such an apparatus, the nitrogen gas can be used more efficiently, and the operating cost can be further reduced.

In this embodiment, the air supply passage 68 and the flow control valve 66 are provided in the same manner as in the first embodiment.
Can be provided to adjust the oxygen concentration.

Next, a third embodiment will be described with reference to FIG. In this embodiment, instead of the nitrogen-rich gas transfer passage 72 in the first embodiment and the second embodiment, the nitrogen-rich gas extraction connecting the passage 41B connected to the discharge side of the oxygen electrode 40B and the nitrogen separator 74 is performed. A passage 124 is provided, and the gas in the passage 41B is supplied to the nitrogen separator 74 through the nitrogen-rich gas extraction passage 124.

In such an apparatus, the oxygen electrode 40B
Since the exhaust gas of the above, that is, the gas already rich in nitrogen due to the consumption of oxygen at the oxygen electrode 40B is supplied to the nitrogen separator 74, the nitrogen separator 74 can separate and purify the nitrogen gas at a high recovery rate. This gas can be used as a fuel cell body sealing gas.

Also in this apparatus, it is possible to use the nitrogen gas more effectively by providing the compressor 118 and the nitrogen gas tank 120 shown in FIG. 5 and storing excess nitrogen gas in the nitrogen gas tank 120. Needless to say.

Further, the present invention is not limited to the above embodiment, but may take the following forms as examples.

(1) In the above embodiment, the nitrogen gas separated and purified by the nitrogen separation device 74 is used as a sealing gas for the fuel cell 38. However, this purified nitrogen gas is used for increasing the pressure and purging the device. It may be.

(2) In the above embodiment, the oxygen separator 7
It is also possible to use a device that preferentially adsorbs oxygen as 0 and a device that preferentially adsorbs nitrogen as the nitrogen separation device 74. In this case, the oxygen is adsorbed and removed by the oxygen separator 70, the gas desorbed is supplied to the oxygen electrode 40B, the nitrogen is adsorbed and removed by the nitrogen separator 74, and the desorbed gas is supplied to the nitrogen use point. What should I do?

(3) In the present invention, as the nitrogen separation device 74 or the oxygen separation device 70, a separation membrane device such as a polymer membrane may be used in addition to the adsorption device.
What is necessary is just to use what permeate | transmits only one of nitrogen and oxygen (generally oxygen) for this separation membrane apparatus.

[0046]

As described above, according to the present invention, a gas is taken out from a gas passage provided in a power generator, nitrogen gas is separated and purified from the gas by a nitrogen separator, and the gas is supplied to a use place of the nitrogen gas. Therefore, at least a part of the nitrogen gas required for the operation of the power generator can be purified in the power generator, and the amount of nitrogen gas that needs to be supplied from the outside should be reduced or set to zero accordingly. Can be. Moreover, since the gas is taken out from the portion where the gas having a higher nitrogen concentration than the air flows, the nitrogen recovery rate by the nitrogen separator can be increased accordingly. Therefore, there is an effect that the power generation cost can be reduced as compared with the conventional case where all necessary nitrogen gas is supplied from the outside.

In particular, in the apparatus according to the first aspect, the above effect is obtained by purifying and separating nitrogen gas from the nitrogen-rich gas after the oxygen gas is separated in the oxygen separation apparatus, and at the same time, the oxygen separation apparatus is used. By introducing the separated and purified oxygen gas into the oxygen electrode of the fuel cell, there is an effect that the output of the fuel cell can be increased as compared with a conventional apparatus in which the raw material air is directly introduced into the fuel electrode.

Further, in the apparatus according to the second aspect, the ratio between the raw material air introduced into the oxygen electrode through the air supply passage and the oxygen gas introduced into the oxygen electrode from the oxygen separator is adjusted by the oxygen concentration adjusting means. This makes it possible to appropriately adjust the oxygen concentration in the oxygen-containing gas supplied to the oxygen electrode. For example, by reducing the oxygen concentration during a period in which power consumption is small, it is possible to save oxygen gas.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing a main part of a power generator according to a first embodiment of the present invention.

FIG. 2 is a flow sheet showing a nitrogen separator and an oxygen separator in the power generator.

FIG. 3 is a graph showing a relationship among an oxygen concentration at an inlet of a fuel cell, an oxygen utilization rate, and an output improvement rate in the power generator.

FIG. 4 is a graph showing a relationship between a raw material gas oxygen concentration and a nitrogen recovery rate in the nitrogen separation device.

FIG. 5 is a flow sheet showing a main part of a power generator according to a second embodiment of the present invention.

FIG. 6 is a flow sheet showing a main part of a power generator according to a third embodiment of the present invention.

FIG. 7 is a flow sheet showing an example of a conventional power generation device.

8 (a), 8 (b) and 8 (c) are graphs showing a consumption period and a consumption amount of nitrogen gas in the power generation device.

[Explanation of symbols]

 Reference Signs List 38 fuel cell 39 seal portion 40A fuel electrode 40B oxygen electrode 62, 76 passage (nitrogen supply passage) 66 flow control valve (oxygen concentration control means) 68 air supply passage 70 oxygen separator 72 nitrogen-rich gas transfer passage 74 nitrogen separator 120 Nitrogen gas tank 124 Nitrogen-rich gas extraction passage

Continued on the front page (72) Inventor Hiroshi Shinkai 1-1-1, Tanabe-Nitta, Kawasaki-ku, Kawasaki-shi Inside Fuji Electric Machinery Co., Ltd. (72) Inventor Hiroshi Miyagawa 1-3-18, Wakihamacho, Chuo-ku, Kobe Co., Ltd. Kobe Steel, Kobe Main Office (72) Inventor Takeyoshi Ueyama 1-3-18, Wakihama-cho, Chuo-ku, Kobe Kobe Steel Co., Ltd. No. 3-18 Kobe Steel, Ltd. Kobe Head Office (56) References JP-A-2-117707 (JP, A) JP-A-64-18906 (JP, A) JP-A-4-227812 (JP, A) JP-A-3-276576 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 8/04

Claims (3)

(57) [Claims] 1. A fuel cell having a fuel electrode and an oxygen electrode, wherein a fuel gas is introduced into the fuel electrode and an oxygen-containing gas is introduced into the oxygen electrode, and exhaust fuel and exhaust air are respectively derived from each electrode. An oxygen separator for separating oxygen gas from the supplied gas, an oxygen supply passage for guiding the oxygen gas separated and purified by the oxygen separator to the oxygen electrode, A nitrogen separation device for separating nitrogen gas from the gas to be separated, a nitrogen-rich gas transfer passage for supplying the remaining nitrogen-rich gas after separation of the oxygen gas in the oxygen separation device to the nitrogen separation device, A nitrogen supply passage for supplying nitrogen gas separated and purified by the separation device to a use place of nitrogen in the power generation device; . 2. A nitrogen circulating apparatus for a power generator using a fuel cell according to claim 1, wherein an air supply passage for introducing raw material air to the oxygen electrode together with oxygen gas separated and purified by the oxygen separator, and the air. A fuel cell power generator comprising: oxygen concentration adjusting means for changing a ratio of raw air introduced into the oxygen electrode through the supply passage and oxygen gas introduced from the oxygen separator to the oxygen electrode. Nitrogen circulation equipment. 3. A fuel cell having a fuel electrode and an oxygen electrode, wherein a fuel gas is introduced into the fuel electrode and an oxygen-containing gas is introduced into the oxygen electrode, and exhaust fuel and exhaust air are respectively derived from each electrode. And a nitrogen-rich device for extracting nitrogen-rich gas derived from the oxygen electrode and introducing it into the nitrogen-separating device. A nitrogen circulating device for a fuel cell power generation device, comprising: a gas extraction passage; and a nitrogen supply passage for supplying nitrogen gas separated and purified by the nitrogen separation device to a nitrogen use point in the power generation device.