JP3557104B2 - Phosphoric acid fuel cell power plant - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a phosphoric acid-type fuel provided with an exhaust gas heat exchanger for recovering combustion exhaust gas discharged from a burner side of a reformer and exhaust heat of air exhaust gas discharged from an air electrode of a fuel cell body. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery power plant, and more particularly to a phosphoric acid fuel cell power plant having a means for extracting high-temperature exhaust heat at a level at which an absorption refrigerator can be operated.
[0002]
[Prior art]
Conventionally, a phosphoric acid-type fuel cell power plant uses phosphoric acid as an electrolyte and electrochemically reacts hydrogen obtained by reforming raw fuel such as natural gas with oxygen in the air to directly generate power. And high power generation efficiency can be obtained.
[0003]
In addition, the phosphoric acid fuel cell power plant has been evaluated as a power plant with extremely low environmental pollutants and low environmental noise.
[0004]
FIG. 4 is a system configuration diagram showing an example of this type of conventional phosphoric acid fuel cell power plant.
[0005]
In FIG. 4, a fuel cell body 1 has a unit cell in which a matrix (not shown) impregnated with phosphoric acid as an electrolyte is sandwiched between a fuel electrode 1a supplied with fuel gas and an air electrode 1b supplied with air. The unit cell is formed by stacking a large number of the unit cells, and electricity is directly generated by an electrochemical reaction between fuel gas and air in the fuel cell body 1.
[0006]
On the other hand, the raw fuel 2 such as natural gas is supplied to the reaction section 3a of the reformer 3, becomes a hydrogen-rich reformed gas 4 by a reforming reaction, and is supplied to the fuel electrode 1a of the fuel cell body 1.
[0007]
The reaction air 5 is supplied to the air electrode 1b of the fuel cell main body 1 by an air supply device 6 such as a blower.
[0008]
At this time, in the fuel cell main body 1, hydrogen in the reformed gas 4 reacts with oxygen in the reaction air 5 to generate electricity.
[0009]
Further, in the fuel cell main body 1, since heat of reaction is generated simultaneously with power generation, a cooling plate 1c is installed in the fuel cell main body 1 for the purpose of keeping the reaction temperature of the fuel cell main body 1 at an appropriate temperature (about 200 ° C.). Then, the battery is cooled by the battery cooling water 7.
[0010]
That is, the cell cooling water 7 has a two-phase flow at the outlet of the fuel cell main body 1 and is separated into steam and water by the steam separator 8. The battery cooling water 7 separated by the steam separator 8 is pressurized by a pump 9, cooled by a cooler 10, and supplied to the fuel cell main body 1.
[0011]
On the other hand, since unreacted hydrogen remains in the reformed gas 4 which has been reacted at the fuel electrode 1a of the fuel cell body 1, it is burned in the burner section 3b of the reformer 3 and the reaction section 3a After becoming a heating source, it is discharged from the reformer 3 as a combustion exhaust gas 11. Further, the reaction air 5 after the reaction is completed at the air electrode 1b of the fuel cell main body 1 is discharged as an air exhaust gas 12.
[0012]
Further, the combustion exhaust gas 11 and the air exhaust gas 12 are combined and cooled by the exhaust gas condenser 13, and then separated into the plant exhaust gas 14 and the condensed water 15. Then, the plant exhaust gas 14 is normally released to the atmosphere as it is, but the condensed water 15 is reused in the plant.
[0013]
That is, generally, the secondary cooling water 16 is passed through the low temperature side of the exhaust gas condenser 13, and the recovered heat from the combustion exhaust gas 11 and the air exhaust gas 12 is supplied to an external heat exchanger 17 through the exhaust heat utilization heat exchanger 17. It is configured to be supplied to the hot water utilization equipment 18.
[0014]
[Problems to be solved by the invention]
However, the exhaust gas condenser 13 used in such a conventional phosphoric acid-type fuel cell power plant mainly aims to condense and recover the water vapor in the combustion exhaust gas 11 and the air exhaust gas 12, so that the secondary cooling water 16 is used. However, there is a problem that it is difficult to reduce the flow rate of hot water, and it is not possible to increase the temperature of hot water for utilizing exhaust heat.
[0015]
An object of the present invention is to provide a phosphoric acid-type fuel cell power plant capable of efficiently recovering heat from exhaust gas and extracting high-temperature exhaust heat at a level that can operate an absorption refrigerator. .
[0016]
[Means for Solving the Problems]
In order to achieve the above object, the phosphoric acid fuel cell power plant according to the first aspect of the present invention has a fuel electrode and an air electrode arranged with a matrix impregnated with phosphoric acid as an electrolyte, A fuel cell body that supplies fuel gas and air to the air electrode to generate electricity by an electrochemical reaction between the fuel gas and air, and a reformed gas containing hydrogen as a main component by reforming raw fuel with steam A reformer that supplies as fuel gas to the fuel electrode of the fuel cell body, an air supply device that supplies air to the air electrode of the fuel cell body, and a combustion exhaust gas discharged from the burner side of the reformer. Heat recovery heat exchanger that recovers exhaust heat of air exhaust gas discharged from the air electrode of the fuel cell body as hot water, and steam contained in combustion exhaust gas and air exhaust gas discharged from the exhaust heat recovery heat exchanger A direct contact heat exchanger that condenses and collects hot water, a cooler that is installed at the cooling water inlet of the fuel cell body and cools with battery cooling water so that the reaction temperature of the fuel cell body is maintained at an appropriate temperature, and a waste heat A single-effect absorption refrigerator that is recovered by a recovery heat exchanger and a direct contact heat exchanger, and is operated by hot water heated by exchanging heat with a cooler; and a flue gas exhausted by the direct contact heat exchanger. And a cooling tower for recovering heat to a temperature at which water vapor in the air exhaust gas is not condensed, and a part of the hot water recovered by the direct contact heat exchanger is supplied to the cooling tower for cooling, and cooling is performed. The water is returned to the direct contact heat exchanger as water .
[0017]
Therefore, in the phosphoric acid type fuel cell power plant according to the first aspect of the present invention, the water vapor contained in the combustion exhaust gas discharged from the burner side of the reformer and the air exhaust gas discharged from the air electrode of the fuel cell body is condensed. By using a direct contact heat exchanger that recovers hot water, the cooling water comes in direct contact with the exhaust gas, so high heat transfer characteristics can be obtained, miniaturization of the exhaust gas condenser can be realized, and exhaust heat recovery By increasing the temperature at which hot water is taken out of the heat exchanger, heat can be efficiently recovered from exhaust gas, and high-temperature exhaust heat at a level that can operate a single-effect absorption refrigerator can be taken out.
In addition, a cooling tower has been added to recover heat to a temperature at which water vapor in the exhaust gas and air exhaust gas does not condense in the direct contact heat exchanger, and part of the warm water recovered in the direct contact heat exchanger is cooled. By supplying the cooling water to the tower and returning it to the direct contact heat exchanger as cooling water, part of the warm water of the direct contact heat exchanger circulates through the cooling tower, so that heat recovery from exhaust gas can be recovered. It is possible to extract the high-temperature exhaust heat at a level that can be operated more efficiently and can operate the absorption refrigerator.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0021]
(First Embodiment)
FIG. 1 is a system configuration diagram of a phosphoric acid fuel cell power plant according to the present embodiment. The same parts as those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted. Only different parts will be described here. .
[0022]
That is, as shown in FIG. 1, the phosphoric acid-type fuel cell power plant according to the present embodiment omits the exhaust gas condenser 13, the exhaust heat utilization heat exchanger 17, and the hot water utilization facility 18 in FIG. Instead, the exhaust heat recovery heat exchanger 19, the single-effect absorption refrigerator 21, the pump 22, the direct contact heat exchanger 23, and the cooling tower 26 are added.
[0023]
The exhaust heat recovery heat exchanger 19 directly uses the exhaust heat of the combustion exhaust gas 11 discharged from the burner side of the reformer 3 and the air exhaust gas 12 discharged from the air electrode 1b of the fuel cell body 1 as a high-temperature heat source. The hot water from the contact heat exchanger 23 is recovered as hot water 20 at about 85 ° C.
[0024]
The direct contact heat exchanger 23 condenses the steam contained in the exhaust gas (combustion exhaust gas and air exhaust gas) 24 from the exhaust heat recovery heat exchanger 19 and recovers it as hot water.
[0025]
The single-effect absorption refrigerator 21 is operated by hot water recovered by the exhaust heat recovery heat exchanger 19 and the direct contact heat exchanger 23 and further heated by exchanging heat with the cooler 10.
[0026]
The cooling tower 26 is for recovering heat to a temperature at which steam in the combustion exhaust gas 11 and the air exhaust gas 12 is not condensed by the direct contact heat exchanger 23, and the pump is operated after the single-effect absorption refrigerator 21 is operated. The hot water 20 supplied via the pipe 22 is returned to the direct contact heat exchanger 23 as cooling water 25.
[0027]
Next, the operation of the phosphoric acid fuel cell power plant according to the present embodiment configured as described above will be described.
[0028]
The description of the operation of the same parts as in FIG. 4 will be omitted, and only the operation of the different parts will be described here.
[0029]
That is, in FIG. 1, the exhaust heat recovery heat exchanger 19 uses the exhaust heat of the combustion exhaust gas 11 from the reformer 3 and the air exhaust gas 12 from the fuel cell body 1 as a high-temperature heat source, and uses hot water 20 Is taken out.
[0030]
This hot water 20 is supplied to the cooler 10 for maintaining the reaction temperature of the fuel cell main body 1 at an appropriate value. After further recovering the exhaust heat of the fuel cell main body 1, the hot water 20 is supplied to the single-effect absorption refrigerator 21. Supplied to operate it.
[0031]
Then, after operating the single-effect absorption refrigerator 21, the hot water 20 is supplied to the cooling tower 26 via the pump 22 to be cooled, returned as the cooling water 25 to the direct contact heat exchanger 23 and circulated.
[0032]
In this case, instead of the exhaust gas condenser 13 described above, a direct contact heat exchanger that condenses steam contained in the combustion exhaust gas 11 from the reformer 3 and the air exhaust gas 12 from the fuel cell body 1 and collects it as hot water. Since the cooling water 25 comes into direct contact with the exhaust gas 24 by using the heat exchanger 23, high heat transfer characteristics can be obtained as compared with the conventional partition type heat exchanger, and the exhaust gas condenser can be downsized. Can be.
[0033]
That is, by using the direct contact heat exchanger 23, the exhaust gas condenser can be miniaturized, and the temperature at which the hot water 20 is taken out of the exhaust heat recovery heat exchanger 19 can be increased to recover heat from the exhaust gas. It is possible to efficiently extract high-temperature exhaust heat at a level that can operate the single-effect absorption refrigerator 21 efficiently.
[0034]
As described above, in the phosphoric acid fuel cell power generation plant of the present embodiment, heat is efficiently recovered from exhaust gas, and high-temperature exhaust heat at a level that can operate the single-effect absorption refrigerator 21 is extracted. Becomes possible.
[0035]
(Second embodiment)
FIG. 2 is a system configuration diagram of the phosphoric acid fuel cell power plant according to the present embodiment. The same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Here, only different parts will be described.
[0036]
That is, as shown in FIG. 2, the phosphoric acid fuel cell power plant according to the present embodiment omits the single-effect absorption refrigerator 21 in FIG. It is configured to include a body-type absorption refrigerator 27.
[0037]
Next, the operation of the phosphoric acid fuel cell power plant according to the present embodiment configured as described above will be described.
[0038]
The description of the operation of the same parts as in FIG. 4 will be omitted, and only the operation of the different parts will be described here.
[0039]
That is, in FIG. 2, the exhaust heat recovery heat exchanger 19 uses the exhaust heat of the combustion exhaust gas 11 from the reformer 3 and the exhaust gas 12 from the fuel cell body 1 as a high-temperature heat source, and uses hot water 20 at about 85 ° C. Is taken out.
[0040]
The hot water 20 is supplied to the cooler 10 for maintaining the reaction temperature of the fuel cell main body 1 at an appropriate value. After further recovering the exhaust heat of the fuel cell main body 1, the hot water 20 is used for single effect and double effect. It is supplied to the body-type absorption refrigerator 27 to operate it.
[0041]
Then, after the single-effect and double-effect integrated absorption refrigerator 27 is operated, the hot water 20 is supplied to the cooling tower 26 via the pump 22 and cooled, and is used as the cooling water 25 as a direct contact heat exchanger. Return to 23 and circulate.
[0042]
In this case, by using the single-effect and double-effect integrated absorption chiller 27 instead of the single-effect absorption chiller 21 described above, the single-effect and double-effect absorption chiller is used. The hot water supplied to 27 can be used effectively.
[0043]
That is, by using the single-effect and double-effect absorption chillers 27, heat recovery from the exhaust gas can be performed more efficiently than in the first embodiment described above. It is possible to extract high-temperature exhaust heat at a level at which the integrated absorption refrigerator 27 can be operated.
[0044]
As described above, in the phosphoric acid fuel cell power plant according to the present embodiment, heat recovery from exhaust gas can be performed even more efficiently, and the single-effect and double-effect integrated absorption refrigerator 27 can be operated. A high level of high-temperature exhaust heat can be extracted.
[0045]
(Third embodiment)
FIG. 3 is a system configuration diagram of the phosphoric acid fuel cell power plant according to the present embodiment. The same parts as those in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted. Only different parts will be described here.
[0046]
That is, as shown in FIG. 3, the phosphoric acid fuel cell power plant according to the present embodiment cools part of the hot water collected by the direct contact heat exchanger 23 in FIG. The cooling is performed by supplying the cooling water 25 to the tower 26 and returning the cooling water 25 to the direct contact heat exchanger 23.
[0047]
Next, the operation of the phosphoric acid fuel cell power plant according to the present embodiment configured as described above will be described.
[0048]
The description of the operation of the same parts as in FIG. 2 is omitted, and only the operation of the different parts will be described here.
[0049]
That is, in FIG. 3, a part of the hot water of the direct contact heat exchanger 23 is supplied again to the cooling tower 26 via the pump 28 to operate the single-effect and double-effect integrated absorption refrigerator 27. Is cooled together with the hot water 20 supplied to the cooling tower 26 via the pump 22, and is returned to the direct contact heat exchanger 23 as the cooling water 25 and circulated.
[0050]
In this case, a part of the hot water of the direct contact heat exchanger 23 is supplied again to the cooling tower 26 via the pump 28 to circulate the hot water, thereby providing a hot water circulation line of the direct contact heat exchanger 23. Accordingly, the flow rate of hot water supplied to the single-effect and double-effect integrated absorption refrigerator 27 can be reduced, so that the temperature of the hot water can be increased.
[0051]
That is, by circulating a portion of the hot water of the direct contact heat exchanger 23 through the pump 28, heat recovery from the exhaust gas is performed more efficiently than in the above-described second embodiment. This makes it possible to extract high-temperature exhaust heat at a level at which the integrated absorption refrigerator 27 for double effect can be operated.
[0052]
As described above, in the phosphoric acid fuel cell power plant of the present embodiment, heat recovery from exhaust gas is performed even more efficiently, and the single-effect and double-effect integrated absorption refrigerator 27 is operated. It is possible to take out high-temperature exhaust heat at a level that can be obtained.
[0053]
(Other embodiments)
In the third embodiment described above, the configuration in which a portion of the hot water of the direct contact heat exchanger 23 is circulated through the pump 28 is a single-effect and double-effect integrated absorption refrigeration as an absorption refrigerator. The case where the present invention is applied to the phosphoric acid type fuel cell power plant equipped with the heat exchanger 27 has been described. However, the present invention is not limited to this. As in the first embodiment described above, a phosphoric acid fuel cell power plant including a single-effect absorption refrigerator 21 as an absorption refrigerator can be similarly applied to achieve the same operation and effect as in the above-described case. It is possible to get.
[0054]
【The invention's effect】
As described above, according to the phosphoric acid fuel cell power plant of the present invention, it is possible to efficiently recover heat from exhaust gas and to extract high-temperature exhaust heat at a level that can operate an absorption refrigerator. It becomes.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram showing a first embodiment of a phosphoric acid fuel cell power plant according to the present invention.
FIG. 2 is a system configuration diagram showing a second embodiment of the phosphoric acid fuel cell power plant according to the present invention.
FIG. 3 is a system configuration diagram showing a third embodiment of a phosphoric acid fuel cell power plant according to the present invention.
FIG. 4 is a system configuration diagram showing an example of a conventional phosphoric acid fuel cell power plant.
[Explanation of symbols]
1 ... fuel cell body,
1a: fuel electrode,
1b ... air electrode,
1c: cooling plate,
2 ... raw fuel,
3 ... reformer,
3a: reaction section,
3b: Burner part,
4 ... reformed gas,
5 ... Reaction air,
6 ... air supply device,
7 ... Battery cooling water,
8 ... steam separator,
9 ... pump,
10 ... cooler,
11 ... combustion exhaust gas,
12 ... Air exhaust gas,
14. Plant exhaust gas,
15 ... condensed water,
19 ... waste heat recovery heat exchanger,
20 ... warm water,
21 ... Single-effect absorption refrigerator
22 ... pump,
23 direct contact heat exchanger,
24 ... exhaust gas,
25 ... cooling water,
26 ... cooling tower,
27… Single-effect and two-effect integrated absorption refrigerator
28 ... Pump.

Claims (1)

A fuel electrode and an air electrode are arranged with a matrix impregnated with phosphoric acid as an electrolyte. A fuel gas is supplied to the fuel electrode and air is supplied to the air electrode, and an electrochemical reaction between the fuel gas and the air is performed. A fuel cell body that generates power by
A reformer that generates a reformed gas containing hydrogen as a main component by steam reforming a raw fuel and supplies the reformed gas as a fuel gas to a fuel electrode of a fuel cell body;
An air supply device for supplying air to the air electrode of the fuel cell body,
A waste heat recovery heat exchanger that recovers, as warm water, combustion exhaust gas discharged from the burner side of the reformer, and exhaust heat of the air exhaust gas discharged from the air electrode of the fuel cell body,
A direct contact heat exchanger that condenses water vapor contained in the combustion exhaust gas and air exhaust gas discharged from the exhaust heat recovery heat exchanger and recovers it as hot water;
A cooler that is installed at a cooling water inlet of the fuel cell body and cools with a cell cooling water so as to maintain a reaction temperature of the fuel cell body at an appropriate temperature;
A single-effect absorption refrigerator that is recovered by the exhaust heat recovery heat exchanger and the direct contact heat exchanger, and is operated by hot water heated by exchanging heat with the cooler ;
A cooling tower for recovering heat to a temperature at which steam in the flue gas and air exhaust gas does not condense in the direct contact heat exchanger,
A part of the hot water recovered by the direct contact heat exchanger is supplied to the cooling tower to be cooled, and returned as cooling water to the direct contact heat exchanger, wherein the phosphoric acid fuel cell power plant is provided. .

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