JP2001052727A - Power generating system by fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power generating system using a solid electrolyte fuel cell having enhanced system efficiency. SOLUTION: In a power generating system by a fuel cell 11 using a solid electrolyte, after exhausted air 15 exhausted from the air electrode 10b of a fuel cell body is used as heat for heat exchange of an air pre-heater 17, a part of it is mixed with air 25 supplied from a recycle line 26 and is used again by preheating the air, and after fuel exhausted gas 12 exhausted from the fuel electrode 10a of the fuel cell body is used as heat for heat exchange of a fuel pre-heater 14, a part of it is mixed with fuel 20 supplied from a recycle line 21 and is used again by preheating the fuel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power generation system using a solid oxide fuel cell for improving system efficiency.

[0002]

2. Description of the Related Art Conventionally, a solid oxide fuel cell (SOFC) has conventionally been used.
ells: Hereinafter referred to as “fuel cell”. ) Have been proposed. The fuel cell uses hydrogen or a hydrocarbon-based gas (for example, methane or the like) as a fuel gas, uses air as an oxidizing agent, and operates at about 1000 ° C.
The battery reaction under high temperature conditions of 1200 ° C)
We are generating electricity.

FIG. 12 shows an example of a conventional power generation system using a fuel cell. A power generation system using a conventional fuel cell has a fuel cell 01 having a fuel electrode 01b and an air electrode 01c on both sides of a solid electrolyte 01a, and the fuel cell 01 is discharged from the fuel electrode 01b and the air electrode 01c of the fuel cell 01, respectively. A combustor 04 that burns the fuel exhaust gas 02 and the exhaust air 03, and a fuel preheater 08 and an air preheater 09 that use the exhaust gas 05 from the combustor 04 to preheat newly supplied fuel 06 and air 07, respectively. And exhaust gas power generation means 011 for generating electric power using the preheated exhaust gas 010. The exhaust gas power generation means 011 includes a steam turbine 012, a generator 013, a condenser 014, and a water supply pump 015. A part of the steam 016 is introduced into the fuel supply line for humidifying the fuel 06.

FIG. 13 shows another example of a power generation system using another conventional fuel cell. In a power generation system using another fuel cell, fuel 022 is supplied to a fuel electrode 021b of the fuel cell 211, and air 023 is supplied to one air electrode 021b. An air preheater 025 is interposed in the supply line 024 of the air 023, and heat is exchanged using heat of the exhaust air 026 discharged from the air electrode 021b. An exhaust gas boiler 028 is provided in an exhaust gas line of the exhaust gas 027 from the air preheater 025. Exhaust air 029 discharged from the exhaust gas boiler 028 is exhausted from a chimney 030, and a part thereof is circulated by a circulation blower 031. Is returned to the air supply line 024, and is mixed with the supplied air 023 to mix the air preheater 025
Has been introduced to.

However, in the conventional fuel cell power generation system as shown in FIG. 12, since the gas flow is unidirectional, a large amount of fuel and air are required to keep the temperature inside the cell within an allowable value. After passing through the combustor 04, the fuel preheater 08, and the air preheater 09 and utilizing the sensible heat of the exhaust gas 05, the exhaust gas 01 is supplied to the power generation means 011 of the bottoming system.
0, the temperature of the inlet gas supplied to the steam turbine 012 of the bottoming system is low, and the bottoming efficiency is low.

On the other hand, in another conventional fuel cell power generation system shown in FIG.
Although the air is preheated by supplying the exhaust air 029 discharged from the exhaust gas 28, the temperature of the exhaust air 029 before being discharged to the chimney 030 is low, and there is a problem that the preheating is not efficient.

In view of the above problems, an object of the present invention is to provide a fuel cell power generation system that improves the power generation efficiency of a fuel cell and the utilization efficiency of the entire system.

[0008]

According to a first aspect of the present invention, there is provided a fuel cell power generation system using a solid electrolyte, wherein exhaust air discharged from an air electrode of a fuel cell body is preheated by air. After using it as heat for the heat exchange of the fuel cell, a part of it is mixed with the supplied air to preheat the air for reuse, and the fuel exhaust gas discharged from the fuel electrode of the fuel cell body is used as a fuel preheater. After being used as heat for heat exchange, a part of the fuel is mixed with the supplied fuel, and the fuel is preheated and reused.

According to a second aspect of the present invention, in the first aspect, the mixed air is supplied to an air preheater by an air circulation blower, and the mixed fuel is supplied to a fuel preheater by a fuel circulation blower. It is characterized by sending.

According to a third aspect of the present invention, in the first aspect, the supply air and the exhaust air are supplied to an air preheater while being mixed by an ejector, and the mixing of the supplied fuel and the fuel exhaust gas is performed. The fuel is supplied to the fuel preheater while being performed by the ejector.

According to a fourth aspect of the present invention, in the second or third aspect, before supplying the air preheated by the air preheater to the air electrode, a small amount of fuel is introduced and heated to a fuel cell reaction temperature. In addition, a small amount of air is introduced before the fuel preheated by the fuel preheater is supplied to the fuel electrode, and the fuel is heated to a fuel cell reaction temperature.

According to a fifth aspect of the present invention, there is provided the combustor according to the first aspect, wherein the remainder of the exhaust air used for preheating the air and the remainder of the fuel exhaust gas used for preheating the fuel are mixed and burned. It is characterized by having.

[0013] The invention of claim 6 is characterized in that, in claim 5, the exhaust gas after combustion from the combustor is used as a heat source of power generation means.

According to a seventh aspect of the present invention, in a power generation system for a fuel cell using a solid electrolyte, exhaust air discharged from the air electrode of the fuel cell body and fuel exhaust gas discharged from the fuel electrode of the fuel cell body are burned. After combustion in a heater and used for preheating air and fuel for supplying high-temperature exhaust gas, a part of the combustion exhaust gas is mixed with supplied air to preheat and reuse the air. I do.

The invention of claim 8 is characterized in that, in claim 7, the mixed air is sent to an air preheater by an air circulation blower.

According to a ninth aspect of the present invention, in the seventh aspect, the supply air and the exhaust air are supplied to an air preheater while being mixed by an ejector.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a fuel cell power generation system according to the present invention will be described below, but the present invention is not limited to these embodiments.

[First Embodiment] A first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram of a fuel cell power generation system. As shown in FIG. 1, a fuel cell power generation system according to the present embodiment includes a fuel cell 11 having a fuel electrode 10a and an air electrode 10b on both sides of a solid electrolyte 10, and a fuel exhaust gas from the fuel electrode 10a. 12 is introduced through the fuel electrode outlet line L _1, the fuel electrode 10
a fuel preheater 14 for preheating the supply fuel 13 via the fuel electrode inlet lines L ₂ to a, the exhaust air 15 from the air electrode 10b is introduced through the air electrode outlet line L _3, the air electrode 10b an air preheater 17 for preheating the supply air 16 through the air electrode inlet lines L _4, these fuel preheater 1
4 and fuel exhaust gas 12 from air preheater 17 and exhaust air 1
5 is introduced through the combustor lines L ₅ and L ₆ and then burned, and the fuel exhaust gas 1 which is branched from the combustor line L ₅ and is not introduced into the combustor 18.
A recycle line 21 for introducing 2 from the outside to the new fuel 20 supplied by the fuel blower 19 is interposed in a fuel preheater inlet line L _7, new fuel 20 and fuel gas 1
The fuel recycle blower 23 supplies the fuel preheater 14 with the mixed fuel 22 whose temperature has risen due to the mixing of the fuel with the fuel combustor 2 and the exhaust air 15 branched from the combustor line L ₆ before being introduced into the combustor 18. Line 26 that introduces air into new air 25 supplied from outside by air blower 24
When it is interposed an air preheater inlet line L _8, new air 2
An air recycle blower 28 for supplying the air preheater 17 with the mixed air 27 whose temperature has risen by mixing the air 5 and the exhaust air 15 to the air preheater 17 and a combustion exhaust gas 29 discharged from an exhaust gas line L ₉ from the combustor 18 are used. And an exhaust gas power generation means 30 for generating electric power. The exhaust gas power generation means 30 is called a so-called bottoming cycle,
Exhaust gas boiler 31, steam turbine 32, and generator 33
And a condenser 34 and a water supply pump 35,
Low-temperature exhaust gas 3 discharged from the exhaust gas boiler 31
6 is discharged from the chimney 37 to the outside.

In the above system, the fuel cell main body 11
After the fuel exhaust gas 12 discharged from the fuel electrode 10a is used for heat exchange in the fuel preheater 14, the
After being mixed with the fuel 20 supplied from the outside by the fuel cell 1 and reused, the exhaust air 15 discharged from the air electrode 10b of the fuel cell body 11 is used for heat exchange in the air preheater 17, and then recycled. The fuel and the air can be efficiently preheated by mixing with the air 25 supplied from the outside and reused, and the remaining fuel exhaust gas 1
2 and the exhaust air 15 are burned in a combustor 18 and the combustor 1
The high-temperature combustion exhaust gas 29 at 8 contributes to the improvement of the power generation efficiency of the exhaust gas power generation means 30 in the bottoming cycle.

That is, as shown in a test example described later,
For example, taking air as an example, when performing heat exchange in an air preheater, the newly introduced air 25 is mixed with the exhaust air 15 supplied by the recycle line 26.
Preheating is performed to some extent, and the heat exchange efficiency in the air preheater 17 increases. Further, since the temperature of the fuel exhaust gas 12 and the exhaust air 15 supplied to the combustor 18 is high, the exhaust gas line L
The temperature of the exhaust gas 29 supplied to the power generation means 30 via ₉ increases. As a result, the thermal efficiency of the exhaust gas boiler is improved, and the power generation efficiency can be improved. Further, since the combustor 18 is installed on the downstream side of the branches of the recycling lines 21 and 26 and immediately before the power generation means 30, the combustion of the fuel exhaust gas 12 and the exhaust air 15 increases the exhaust gas temperature,
The gas supplied from the power generation means 30 to the exhaust gas boiler 31 can be heated to a high temperature, and the power generation efficiency in the bottoming cycle is also improved.

<Test Example 1> The heat mass balance of the power generation system showing the effects of the present invention will be described below. FIG. 2 is an example of a heat mass balance map of the power generation system shown in FIG. Here, in FIG. 2, T indicates the temperature (° C.), and M indicates the mass amount (× 10 ³ Mmol / h). Table 1 shows the system specifications of the system shown in FIG.

[0022]

[Table 1]

First, although the discharged fuel exhaust gas 12 has a decrease from 1041 ° C. to 645 ° C. in the heat exchange of the fuel preheater 18, the fuel exhaust gas 12 is mixed with the fuel 20 newly introduced through the recycle line 21. And recirculation, the temperature of the newly supplied fuel 20 becomes 2
Increase to 59 ° C. Therefore, the heat exchange load of the fuel preheater 18 is reduced as a whole. This is the same on the air side. Moreover, the rest of the exhaust air 15 and fuel gas 12 that is not branched to the recycle line 21 and 26 is burned in the combustor 18, where 930 ° C. to generate a hot exhaust gas 29 that, via the exhaust gas line L ₉ the The high-temperature exhaust gas 29 can be supplied to the gas power generation means 30. As a result, high-temperature steam can be obtained in the exhaust gas boiler 31, and power generation efficiency is improved. As a result of the present invention, as shown in Table 1, a power generation system without any loss can be constructed. Advantageous Effects of Invention According to the present invention, it is possible to reduce the energy required for heating and equalizing the temperature of the system with a small amount of air and a small amount of fuel, and to improve the reliability of the fuel cell. In addition, since the fuel exhaust gas that has not contributed to the reaction is circulated, the external supply of steam required for fuel reforming is not required, which simplifies the apparatus and improves the fuel utilization rate. The efficiency of the system can be improved.

[Second Embodiment] A second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a schematic diagram of a fuel cell power generation system. In the system according to the first embodiment shown in FIG. 1, the newly supplied fuel 20 and the fuel exhaust gas 12 are mixed by connecting a line so that the natural mixture is guided to the fuel preheater 14 by the recycle blower 23. However, in the present embodiment shown in FIG. 3, the mixing of the new fuel and the fuel exhaust gas and the mixing of the new air and the exhaust air are forcibly mixed using an ejector, and the mixture is supplied to the preheater. It is a system to send. Since the other configuration is the same as that of FIG. 1, the same reference numerals as those in FIG. 1 are assigned and the description thereof is omitted. As shown in FIG. 3, in the present system, the fuel exhaust gas 12 and the newly supplied fuel 20
Is mixed by using an ejector 38, and mixing of the exhaust air 15 and the newly supplied air 25 is performed by using an ejector 39. Thus, the ejector 38,
By using 39, gas recycling in a high temperature region where an existing recycling blower cannot be used becomes possible.

[Third Embodiment] A third embodiment of the present invention will be described with reference to FIG. FIG. 4 is a schematic diagram of a fuel cell power generation system. The fuel cell power generation system shown in FIG. 4 has a configuration in which a partial combustion unit is installed when the heating temperature of the fuel gas 13 and the air 16 before supply to the fuel cell 11 is low in the system of FIG. Here, as the partial combustion means, for example, as shown in FIG. 4, if the combustion fuel preheater 41 interposed in the fuel supply line L ₂ which has been preheated in advance fuel heat exchanger 14, from the outside By supplying a small amount of the air 25, a part of the preheated fuel 13 and the supplied air 25 are burned to raise the temperature of the supplied gas, thereby reheating the fuel itself. On the other hand, if the combustion fuel preheater 42 disposed to the air supply line L _4, which is preheated in advance air heat exchanger 17, by supplying a small amount of fuel 20 from the outside, one preheated air 16 The part itself and the supplied fuel 20 are burned to raise the temperature of the supply gas, thereby reheating the air itself.

According to the present embodiment, in order to raise the gas temperature by 30 ° C., it is normally necessary to provide a heat exchanger having a larger heat transfer area. Instead, the temperature can be easily increased from, for example, 920 ° C. to 950 ° C., which is an efficient gas temperature of the fuel cell.

[Fourth Embodiment] A fourth embodiment of the present invention will be described with reference to FIG. FIG. 5 shows an example of a system using a fuel cell module that embodies the fuel cell portion of the system of FIG.

As shown in FIG. 5, the fuel cell module according to the present embodiment has a module body 54 having a partition wall 51 and an interior divided into an upper room 52 and a lower room 53. A fuel cell stack 55 provided in a lower chamber 53 of the module main body 54 and having a plurality of power generation films provided with an air electrode and a fuel electrode on both sides; and a lower surface side (ground side) of the fuel cell stack 55 And a fuel chamber 56 for supplying the fuel 13 sufficiently heated to the power generation temperature.
And an air chamber 57a and exhaust air 15 which are provided on both side surfaces of the fuel cell stack 55 to supply the air 16 sufficiently heated to the power generation temperature to the fuel cell stack 55.
Air chamber 57b for discharging air, an air preheater 17 provided in the upper chamber 52 of the module main body 54 for heating the air 16 supplied to the air chamber 57a, and a base body 58 of the module main body 54 The fuel chamber 56 is provided
And a fuel preheater 18 for heating the fuel 13 supplied to the fuel cell. Here, in the present embodiment, the upper chamber 52 in which the module main body 54 is divided by the partition wall 51 is referred to as an air preheating chamber in which the air preheater 17 for preheating the air 25 supplied from the outside is provided, and the lower chamber 53 Is referred to as a stack chamber for storing the fuel cell stack 55.

It should be noted that the fuel exhaust gas 12 having a configuration other than that described above is used.
And a fuel circulation blower 23 for supplying a mixed gas 22 mixed with the fuel exhaust gas 12 and the new fuel 20 supplied by the fuel blower 19 to the fuel preheater 14.
And a recycle line 26 for the exhaust air 15,
Circulating blower 28 for supplying mixed gas 27 mixed with air and fresh air 25 supplied by air blower 24 to air preheater 17, combustor 18 for burning fuel exhaust gas 12 and exhaust air 15, and combustor 18 Cycle power generation system 30 that generates power using exhaust gas 29 from
Are the same as those shown in FIG. Since the combustor 18 is not provided in the module of the present embodiment, but is provided in the vicinity of the gas turbine 31, the fuel exhaust gas 12 and the exhaust air 15 are circulated and transferred as they are, and the gas turbine 31 is transferred. Is burned in the combustor 18 provided in the vicinity of the above, so that heat loss due to the circulation of high-temperature exhaust gas after combustion can be prevented.

In the present embodiment, as shown in FIG. 6, the fuel cell stack 55 is arranged in a small number (for example, 9 stages) of the sub-stacks 61 with the power generation films standing up through the interconnectors alternately. The sub stacks are arranged in a plurality of rows (for example, 10 rows) using a current collecting member (not shown).
(Rows: 61-1 to 61-10) These are alternately connected to form a wagon-shaped horizontal stack. An air supply pipe 62 and an air discharge pipe 63 are connected alternately to the left and right sides of the wagon-shaped horizontal stack 55. For example, the first sub-stack 61-
Taking 1 as an example, the air 16 supplied from the air preheating chamber is supplied to the left air chamber 57a, and the exhaust air 15 is discharged from the right air chamber 57b after the battery reaction. The sub-stacks 61-1 and 61-10 located at both ends of the wagon-shaped horizontal stack 55 are provided with current collecting plates 65 having current collecting rods 64, respectively, to collect power. .

[Fifth Embodiment] A fifth embodiment of the present invention will be described with reference to FIG. FIG. 7 shows an example of a system using a fuel cell module that embodies the fuel cell portion of the system of FIG.

In the fuel cell module according to the present embodiment, two gas-impermeable partitions 71 and 72 are provided, and the interior is divided into an upper room 73, an intermediate room 74, and a lower room 75. A fuel cell stack 77 provided in a lower chamber 75 of the module main body 76 and having a power generation film provided with an air electrode and a fuel electrode on both surfaces thereof; A fuel chamber 78 provided on the lower surface side for supplying the fuel 13 and air arranged on both side surfaces of the fuel cell stack 77 for supplying air 16 to the fuel cell stack 77 and discharging exhaust air 15. It comprises a chamber 79 and an air preheater 17 provided in the upper chamber 73 of the module main body 76 and heating the air 16 supplied to the air chamber 79. The air chamber 79 is divided into upper and lower parts by a partition wall 79a. The upper chamber is a discharge air chamber 79b, the lower chamber is a supply air chamber 79c, and the air that communicates the air preheater 17 with the supply air chamber 79c. Supply pipe (inner pipe) 80
And an air discharge pipe (outer pipe) which covers the periphery of the air supply pipe 80 and communicates with the intermediate chamber 74 provided between the upper chamber 73 and the lower chamber 75 of the module body 76 and the exhaust air chamber 79b. ) 81 are provided to form a double pipe structure.

Here, in this embodiment, the upper chamber 73 divided by the gas-impermeable partition walls 71 and 72 serves as an air preheating chamber, and the lower chamber 75 contains a fuel cell stack 77 in the present embodiment. The intermediate room 74 is an exhaust air storage chamber for temporarily storing the exhaust air 15.

Then, the air 16 preheated by the air preheater 17 is introduced into the supply air chamber 79c through the air supply pipe 80, and the exhaust air 15 from the exhaust air chamber 79b is interposed through the air exhaust pipe 81. It is sent to room 74. Further, the fuel exhaust gas 12 from the fuel cell stack 77
Is discharged to the lower chamber 75, is recycled and introduced into the fuel preheater 18, and then a part thereof is mixed with the newly supplied fuel 20 and recycled by the recycle line 21. The exhaust air 15 is preheated to newly supplied air 25 by an air preheater 17 and then discharged to the outside. A part of the exhaust air 15 is used for preheating air in a recycle line 26, and the rest is introduced into a combustor 18 to be fueled. Combustion with the exhaust gas 12 generates a high-temperature exhaust gas 29 here, which can be supplied to the gas power generation means 30 via the exhaust gas line. As a result,
In the exhaust gas boiler 31, high-temperature steam can be obtained, and power generation efficiency is improved.

Further, since the exhaust air storage chamber which temporarily stores the exhaust air 15 which is the intermediate chamber 75 is provided below the air preheating chamber which is the upper chamber 73, the entire lower portion of the air preheater 17 is kept warm. it can.

In the present embodiment, as shown in FIG. 8, the fuel cell stack 77 is arranged in a small number (for example, 9 stages) of the sub-stacks 77 alternately with interconnectors in a state where the power generation films are erected. The sub stacks are arranged in a plurality of rows (for example, 10 rows) using a current collecting member (not shown).
Row) and alternately connected to form a wagon-shaped horizontal stack. Further, in the present embodiment, the air chamber 79 provided on both sides of the stack 77 is provided with the air preheater 17.
The air 16 preheated to a high temperature by the air supply pipe (inner pipe)
The exhaust air 15 is supplied to the inside through the outlet 80 and discharged obliquely upward after the battery reaction.
1 to the exhaust air storage chamber of the intermediate room 74, where the exhaust air 15 stored therein is heated by the air preheater 17 to the new air 25, and thereafter, the combustion exhaust gas 28 is discharged to the outside. 23 is introduced into the outside air 20
Heat exchange. As described above, since the supply of the air 16 and the discharge of the exhaust air 15 are performed through the double pipes (the air supply pipe 80 and the air exhaust pipe 81), the heat of the exhaust air is supplied without using any special device. And the function of a heat exchanger can be imparted to the portion.

[Sixth Embodiment] A sixth embodiment of the present invention will be described with reference to FIG. FIG. 9 shows an application example of the fuel cell power generation system of FIG.

In the first embodiment shown in FIG. 1, the newly supplied fuel and air are both preheated.
In this embodiment, an example of a system for preheating only newly supplied air will be described.

As shown in FIG. 9, the fuel cell power generation system according to the present embodiment has a fuel cell 11 having a fuel electrode 10a and an air electrode 10b on both sides of a solid electrolyte 10.
A combustor 18 for burning the fuel exhaust gas 12 from the fuel electrode 10a and the exhaust air 15 from the air preheater 17;
A fuel preheater 14 that heats newly introduced fuel 20 using heat of exhaust gas 29 after combustion in the combustor 18;
An air preheater 17 for heating the air by using the heat of the exhaust gas 29 from the fuel preheater 14, and new air supplied from the outside by a part of the exhaust gas 29 from the air preheater 17 by the air blower 24. Recycling line 26 introduced to 25
And an air recycle blower 28 that supplies mixed air 27 whose temperature has risen by mixing new air 25 and exhaust gas 29 to the air preheater 17, and an exhaust gas that uses the exhaust gas 29 from the air preheater 17 to generate power And a power generation means 30. The exhaust gas power generation means 30 is referred to as a so-called bottoming cycle, and includes an exhaust gas boiler 31, a steam turbine 32, a generator 33, a condenser 34, and a water supply pump 35.
The low-temperature exhaust gas 36 discharged from 1 is discharged from a chimney 37 to the outside.

In the above system, the fuel cell body 11
Exhaust gas (1040 ° C) discharged from the fuel electrode 10a
12 and air exhausted from the air preheater 17 (1040 ° C.) 15
Is burned in the combustor 18 to obtain a high-temperature exhaust gas (1500 ° C.). The fuel 20 and the air are preheated sequentially by the fuel preheater 14 and the air preheater 17, and the temperature of the exhaust gas 29 becomes 830 ° C. However, by mixing the exhaust gas with the newly introduced air 25 through the recycling line 26, the temperature of the mixed air is increased to 650 ° C., and the load of heat exchange in the air preheater is reduced. I have. Further, the power generation efficiency of the exhaust gas power generation means 30 in the bottoming cycle is also improved.
In addition, the fuel preheater 14 and the air preheater 17
In the case of performing heat exchange of (00 ° C. or more), for example, a ceramic heat exchanger may be used.

<Test Example 2> The heat mass balance supplied to the power generation system of the present invention and the prior art for verifying the effect of the present invention will be described below. FIG. 10 is an example of an air side heat mass balance map of the power generation system shown in FIG. Here, in FIG. 10, T indicates a temperature (° C.).

FIG. 10A shows a test product of the present invention, and FIG. 10B shows a comparative product of the comparative example shown in FIG. The test system circulates through a recycling line 26A before supplying exhaust air 15 from the cathode of the fuel cell to the exhaust gas boiler 31 (FIG. 10).
(A)) A conventional system in which a recycling line is not provided on the upstream side of the exhaust gas boiler 31 but a recycling line 26B is provided on the downstream side of the exhaust gas boiler 31 and recycled to the air preheater 17 (FIG. 10B). And compared. In order to make the conditions uniform, the circulation amounts of the two are set to be the same, the heat transfer coefficient of the heat exchange of the air preheater is kept constant at 30 Kcal / m ² h ° C., and the exhaust gas composition is kept as air. In addition,
The temperature of the exhaust air 15 supplied to the air preheater 17 is 110
FIG. 9 differs from FIG. 9 in that the temperature is set to 0 ° C. and a temperature at which heat can be exchanged by an iron heat exchanger. Table 2 shows the results.

[0043]

[Table 2]

As shown in Table 2 and FIG. 10 (a), when the exhaust air 15 immediately after being discharged from the air preheater 17 is recirculated through the recycling line 26A, the exhaust gas boiler, which is the efficiency on the bottoming cycle side, is used. The production of hot water at the plant is more than 1.5 times higher than that of the comparative example.
The total amount of the required electric heating area of 7 and the exhaust gas boiler is also 9.41m
It turned out that it was only ² and very few.

[Seventh Embodiment] A seventh embodiment of the present invention will be described with reference to FIG. FIG. 11 is a schematic diagram of a fuel cell power generation system. In the system according to the sixth embodiment shown in FIG. 9, the newly supplied air 25 and the exhaust gas 29 are mixed by connecting a line, and the natural mixture is guided to the air preheater 17 by the recycle blower 28. However, in the present embodiment shown in FIG. 11, a system is used in which the mixing of the new air 29 and the exhaust gas 29 is forcibly mixed using an ejector and is supplied to a preheater. The other configuration is the same as that of FIG.
The same reference numerals as those in FIG. 9 are used and the description thereof is omitted.

As shown in FIG. 11, in the present system, the exhaust gas 29 and the newly supplied air 25 are mixed using an ejector 38. By using the ejector 38 in this manner, gas can be recycled in a high-temperature region where an existing recycling blower cannot be used.

[0047]

As described above, according to the first aspect of the present invention, in the fuel cell power generation system using the solid electrolyte, the exhaust air discharged from the air electrode of the fuel cell body is supplied to the air preheater. After using it as heat for heat exchange, a part of it is mixed with supplied air to preheat the air and reuse it, and the fuel exhaust gas discharged from the fuel electrode of the fuel cell body is heated by the fuel preheater. After being used as the heat of exchange, a part of the fuel is mixed with the supplied fuel and the fuel is preheated and reused, so that the fuel and the air can be efficiently preheated. Further, the fuel utilization can be improved.

According to a second aspect of the present invention, in the first aspect, the mixed air is supplied to an air preheater by an air circulation blower, and the mixed fuel is preheated by a fuel circulation blower. Since the gas is sent to the vessel, the temperature of the gas after heat exchange is low, and the gas can be sent by a low-temperature blower.

According to a third aspect of the present invention, in the first aspect, the supply air and the exhaust air are supplied to an air preheater while mixing the supply air and the exhaust air by an ejector. Since the fuel is supplied to the fuel preheater while mixing is performed by the ejector, gas can be recycled in a high-temperature region where an existing recycling blower cannot be used.

According to a fourth aspect of the present invention, in the second or third aspect, a small amount of fuel is introduced before supplying the air preheated by the air preheater to the air electrode to reduce the fuel cell reaction temperature. In addition to heating, a small amount of air is introduced before the fuel preheated by the fuel preheater is supplied to the fuel electrode, and heated to the fuel cell reaction temperature, so that the fuel cell can be provided without a heat exchanger having a large heat transfer area. Can be easily raised to an efficient gas temperature.

According to a fifth aspect of the present invention, in the first aspect, the remainder of the exhaust air used for preheating the air and the remainder of the fuel exhaust gas used for preheating the fuel are mixed and burned. Since the combustor is provided, the remaining fuel exhaust gas and exhaust air can be burned in the combustor to obtain high-temperature combustion exhaust gas.

According to the invention of claim 6, in claim 5, the exhaust gas after combustion from the combustor is used as a heat source of the power generation means, so that the remaining fuel exhaust gas and exhaust air are burned in the combustor. Thus, the high-temperature combustion exhaust gas contributes to the improvement of the power generation efficiency of the exhaust gas power generation means in the bottoming cycle.

According to the invention of claim 7, in the fuel cell power generation system using the solid electrolyte, the exhaust air discharged from the air electrode of the fuel cell body and the fuel exhaust gas discharged from the fuel electrode of the fuel cell body are Is burned in a combustor and used for preheating air and fuel for supplying high-temperature exhaust gas, respectively, and then a part of the combustion exhaust gas is mixed with supplied air to preheat the air and reuse it. The air can be efficiently preheated, and the heat exchanger can be made more compact.

According to the eighth aspect of the present invention, in the seventh aspect, the mixed air is supplied to the air preheater by the air circulation blower.
Feeding is possible with a low-temperature blower.

According to the ninth aspect of the present invention, in the seventh aspect, since the supply air and the exhaust air are supplied to the air preheater while being mixed by the ejector, the high temperature at which the existing recycling blower cannot be used. Gas recycling in the area becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a fuel cell power generation system according to a first embodiment.

FIG. 2 is a heat mass balance map of the power generation system shown in FIG.

FIG. 3 is a schematic diagram of a fuel cell power generation system according to a second embodiment.

FIG. 4 is a schematic diagram of a fuel cell power generation system according to a third embodiment.

FIG. 5 is a schematic diagram of a fuel cell power generation system according to a fourth embodiment.

FIG. 6 is a perspective view of a stack according to a fourth embodiment.

FIG. 7 is a schematic diagram of a fuel cell power generation system according to a fifth embodiment.

FIG. 8 is a perspective view of a stack according to a fifth embodiment.

FIG. 9 is a schematic diagram of a fuel cell power generation system according to a sixth embodiment.

10 is a heat mass balance map of the power generation system shown in FIG.

FIG. 11 is a schematic diagram of a fuel cell power generation system according to a seventh embodiment.

FIG. 12 is a schematic view of a conventional fuel cell power generation system.

FIG. 13 is a schematic diagram of a conventional fuel cell power generation system.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 solid electrolyte 10 a fuel electrode 10 b air electrode 11 fuel cell 12 fuel exhaust gas 13 fuel 14 fuel preheater 15 exhaust air 16 air 17 air preheater 18 combustor 19 fuel blower 20 new fuel 21 recycling line 22 mixed fuel 23 fuel recycling blower 24 Air blower 25 New air 26 Recycling line 27 Mixed air 28 Air recycling blower 29 Combustion exhaust gas 30 Exhaust gas power generation means 31 Exhaust gas boiler 32 Steam turbine 33 Generator 34 Condenser 35 Water pump

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yasuhiko Ikemoto 1-1-1, Wadasaki-cho, Hyogo-ku, Kobe-shi, Hyogo F-term in Mitsubishi Heavy Industries, Ltd. Kobe Shipyard (reference) 5H026 AA06 5H027 AA06 BA19 BC19 DD02

Claims (9)

[Claims] In a power generation system for a fuel cell using a solid electrolyte, exhaust air discharged from an air electrode of a fuel cell body is used as heat for heat exchange of an air preheater, and a part of the air is supplied. And preheats the air for reuse, and uses the fuel exhaust gas discharged from the fuel electrode of the fuel cell body as heat for heat exchange of the fuel preheater, and then uses a part of the fuel for the supplied fuel. A fuel cell power generation system wherein the fuel is mixed, preheated, and reused. 2. The method according to claim 1, wherein the mixed air is supplied to an air preheater by an air circulation blower, and the mixed fuel is supplied to a fuel preheater by a fuel circulation blower. Fuel cell power generation system. 3. The fuel preheater according to claim 1, wherein the supply air and the exhaust air are supplied to an air preheater while being mixed by an ejector, and the supply fuel and the fuel exhaust gas are mixed by an ejector. A fuel cell power generation system characterized in that the fuel cell power is supplied to a fuel cell power generation system. 4. The method according to claim 2, wherein a small amount of fuel is introduced before the air preheated by the air preheater is supplied to the air electrode, the fuel is heated to a fuel cell reaction temperature, and the fuel preheater is used. A fuel cell power generation system characterized in that a small amount of air is introduced before supplying preheated fuel to a fuel electrode and heated to a fuel cell reaction temperature. 5. The combustor according to claim 1, further comprising a combustor for mixing and burning the remainder of the exhaust air used for preheating the air and the rest of the fuel exhaust gas used for preheating the fuel. Fuel cell power generation system. 6. The fuel cell power generation system according to claim 5, wherein the exhaust gas after combustion from the combustor is used as a heat source of a power generation unit. 7. A fuel cell power generation system using a solid electrolyte, wherein a combustor combusts exhaust air discharged from an air electrode of the fuel cell body and fuel exhaust gas discharged from a fuel electrode of the fuel cell body to generate a high-temperature fuel. A fuel cell power generation system characterized in that after exhaust gas is used for preheating air and fuel, a part of the combustion exhaust gas is mixed with supplied air to preheat and reuse the air. 8. The fuel cell power generation system according to claim 7, wherein the mixed air is supplied to an air preheater by an air circulation blower. 9. The fuel cell power generation system according to claim 7, wherein the supply air and the exhaust air are supplied to an air preheater while being mixed by an ejector.