JPH10334932A - Fuel cell power generating system and exhaust heat recovery method therein - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently put exhaust heat recovery from steam as well as reduce cost. SOLUTION: A cell cooling water system is a circulating system for circulating a fuel cell body 1, a steam separator 2, a cell cooling water circulating pump 3, a steam generator 10 and a heat exchanger 4 for adjusting the temperature. As an exhaust heat recovery system, a circulating system is provided for circulation through the steam generator 10, an exhaust heat recovery device 7 and a pump 19. The steam generator 10 is disposed downstream of the cell cooling water circulating pump 3 in the cell cooling water system. Part of cell cooling water is branched downstream of the steam generator 10, to be returned downstream of the steam separator 2 via a water treatment device 8 and a pump 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a fuel cell power generation system and a method of recovering exhaust heat in a fuel cell power generation system, and more particularly to an effective recovery of exhaust heat.

[0002]

2. Description of the Related Art A fuel cell power generation system uses a chemical reaction between hydrogen obtained by reforming fuel such as city gas and propane gas and oxygen obtained from air or the like to convert chemical energy into electric energy. This is a power generation system that extracts DC power by converting the power into DC power. As described above, the fuel cell power generation system has a high power generation efficiency because it is a system that directly obtains current from energy due to a chemical reaction. Furthermore, when the low-temperature exhaust heat at the hot water level and the high-temperature exhaust heat at the steam level are recovered and all the recovered exhaust heat is used, the overall energy utilization efficiency reaches 80% or more.

[0003] Furthermore, fuel cell power generation systems do not use fuel combustion, so they emit less air pollutants and have low noise, so they are highly evaluated as next-generation clean energy systems. In addition, among the recovered exhaust heat, high-temperature exhaust heat has a high utility value as a drive source of an absorption refrigerator or a steam turbine, and therefore, in recent years, a demand for steam extraction has become strong.

FIGS. 4 and 5 each show an example of the configuration of a conventional fuel cell power generation system. That is, in the fuel cell power generation system, as shown in FIGS. 4 and 5, the fuel cell main body 1 has a fuel electrode 1a, an air electrode 1b, and a cell cooling plate 1c, and fuel gas is supplied to the fuel electrode 1a.
The reaction air is supplied to the air electrode 1b to generate power.
Battery cooling water for absorbing heat generated from the fuel cell is passed through the battery cooling plate 1c, and heat generated during power generation is recovered by exchanging heat with the battery cooling water. The heated battery cooling water is led to the gas-water separator 2 in a state where the two-phase flow is formed into a gas and a liquid. The steam / water separator 2 is separated into gas and liquid by heating in the fuel cell main body 1.
This is a device for separating the phased battery cooling water into steam 2a and cooling water 2b.

In the structure shown in FIG. 4, the steam separated here is sent to the reformer and the exhaust heat recovery unit 7, and the steam sent to the reformer is used for the reforming reaction of the fuel gas. . On the other hand, the exhaust heat recovery device 7 is a heat exchanger for transmitting the exhaust heat inside the system to the outside, and the steam sent to the exhaust heat recovery device 7 is condensed by depriving the exhaust heat here. It is converted into water and sent to a water treatment device 28. The water treatment device 28 is a device for purifying battery cooling water using an ion exchange resin or the like.

[0006] The condensed water purified by the water treatment device 28 is pressurized by the circulation pump 9 and returned to the downstream of the steam separator 2. The returned condensed water joins the battery cooling water separated by the steam separator 2 and is sent to the battery cooling water circulation pump 3. The pump 3 is a pump that pressurizes the battery cooling water to circulate.

The battery cooling water pressurized by the pump 3 is sent to a temperature adjusting heat exchanger 4. The heat exchanger 4 is a device for cooling the battery cooling water to a specified temperature at the inlet of the battery cooling plate 1c. The battery cooling water cooled here is guided again to the battery cooling plate 1c, and is used again for exhaust heat recovery by power generation.

The method of recovering exhaust heat in the fuel cell power generation system having such a configuration is referred to as a direct extraction method since exhaust heat is directly recovered from excess high-temperature steam obtained from the steam separator 2. The circulation system including the battery cooling plate 1c, the water / water separator 2, the battery cooling water circulation pump 3, and the heat exchanger 4 for temperature adjustment is referred to as a battery cooling water system.

However, in the case of the direct removal method shown in FIG. 4, the battery cooling water system and the exhaust heat recovery device 7 are configured as the same piping system through which the cooling water flows. Therefore, the condensed water generated on the exhaust heat recovery side (secondary system) is returned to the battery cooling water (primary system) side. This condensed water contains impurities mainly composed of phosphoric acid. Therefore, such integration of the piping system means that poor quality water flows from the secondary system into the primary system, and the primary system including the fuel cell body 1 can be corroded as it is. There is. Therefore, conventionally, it was necessary to provide a high-performance water treatment device 28 in order to avoid this corrosion.

However, in such a configuration, since the volume of the water treatment device 28 occupying the system becomes large, it is difficult to reduce the size of the entire system. In addition, the water treatment device 28
Not only is the equipment cost high, but also the continuous cost of water treatment, such as the replacement of ion exchange resin, increases, making it difficult to reduce costs.

FIG. 5 shows another configuration example in which such deterioration of the water quality is not caused. The same members as those in the configuration example shown in FIG. Omitted. The feature of the configuration shown in FIG. 5 is that, in addition to the battery cooling water system, a circulation system (exhaust heat recovery system) for exhaust heat recovery that is isolated from the cooling water system is provided.

That is, in FIG. 5, the cooling water separated by the steam / water separator 2 circulates in the battery cooling system, and a steam generator 10 is provided between the steam / water separator 2 and the pump 3 in the battery cooling water system. Is provided. This steam generator 10 is a heat exchanger for recovering exhaust heat from the battery cooling water system,
On the high-temperature heating side (primary side), battery cooling water flows as part of the battery cooling water system. In addition, steam generator 1
The low-temperature heated side (secondary side) of 0 is a part of the exhaust heat recovery system. The exhaust heat recovery system in FIG. 5 is a circulation system that returns from the steam generator 10 to the steam generator 10 via the exhaust heat recovery device 7 and the circulation pump 19. The circulation pump 19 is a pump for circulating the secondary cooling water in the exhaust heat recovery system. The heat medium of the exhaust heat recovery system, that is, the secondary cooling water is circulated in the exhaust heat recovery system by this pump. doing. The exhaust heat recovery system and the battery cooling water system are configured without any mutual material flow.

In such a conventional example, the exhaust heat of the battery cooling water (primary system) is transmitted to the medium of the exhaust heat recovery system in the steam generator 10 which has no flow of the substance with the primary system. Since the water is recovered, water of poor quality in the secondary system does not flow into the primary system. Therefore, a specially high-performance water treatment device is not required, and the cost is reduced. The method of exhaust heat recovery in the fuel cell power generation system having such a configuration is referred to as an indirect extraction method because heat during power generation is indirectly recovered by the medium to be heated of the steam generator 10.

The cell cooling system is also called a primary system or a primary cooling system in that the fuel cell main body 1 is directly cooled, and the cooling water of the battery cooling system, that is, the primary cooling system is a cell cooling water or a secondary cooling system. Can be called water. The exhaust heat recovery system is also called a secondary system or a secondary cooling system because the heat generated by the fuel cell body 1 is indirectly recovered through cooling water of the primary cooling system. That is, the heat medium of the secondary cooling system can be called secondary cooling water.

[0015]

However, the indirect extraction method shown in FIG. 5 also has a problem that it is difficult to obtain steam having a high temperature level. That is, FIG.
Is transmitted to the medium of the exhaust heat recovery system separated from the battery cooling water system by transferring the thermal energy of the water separated by the steam-water separator 2 to generate steam from the medium. It is typical. Therefore, the efficiency of heat exchange is limited, and it has been difficult to obtain steam having a high temperature level.

Furthermore, as shown in the configuration example of FIG. 5, when the steam generator 10 is provided between the steam separator 2 and the battery cooling water circulating pump 3, there are the following problems. That is, even if the cooling water going to the steam generator 10 has a sufficiently high pressure,
At the outlet of the steam generator 10, the water supply pressure decreases due to resistance, temperature drop, and the like when passing through a heat transfer tube or the like provided in the steam generator 10. When such a pressure loss in the steam generator 10 is large, the absorption pressure of the pump 3 relatively lowers to the saturated vapor pressure of water or less, so that bubbles are generated in the cooling water and cavitation in the pump 3 is likely to occur. There was a problem of becoming.

The present invention has been proposed to solve the above-mentioned problems of the prior art. It is an object of the present invention to efficiently recover exhaust heat from steam and to reduce the cost of fuel. An object of the present invention is to provide a method for recovering exhaust heat in a battery power generation system and a fuel cell power generation system.

More specifically, an object of the present invention is to prevent corrosion of a primary system by recovering exhaust heat with a heat exchanger to a battery cooling water system and a heat medium having no substance flowing therethrough,
By providing a heat exchanger for exhaust heat recovery downstream of the primary circulation pump, cavitation in the circulation pump is prevented (claims 1 and 7). Another object of the present invention is to reheat the purified battery cooling water with exhaust heat recovered from the upstream side of the water treatment apparatus, thereby increasing the temperature of the battery cooling water and steam in the battery cooling water system to a high temperature. It is to maintain (claim 2).

Another object of the present invention is to improve the exhaust heat recovery efficiency by recovering the exhaust heat of the burner combustion exhaust gas of the reformer into a part of the battery cooling water. , 8). Another object of the present invention is to maximize the absorption of exhaust heat from the burner combustion exhaust gas by branching the battery cooling water for recovering the exhaust heat of the burner combustion exhaust gas from the downstream of the heat exchanger at the lowest temperature. (Claim 5).

[0020]

In order to achieve the above object, according to the present invention, there is provided a battery cooling water system for absorbing heat generated from a fuel cell body into the battery cooling water, and circulating the battery cooling water. And a heat exchanger for collecting exhaust heat from the battery cooling water, the battery cooling water system has no flow with the heat medium of the heat exchanger. The heat exchanger is configured as a closed system, and the heat exchanger is provided downstream of the circulation pump. An exhaust heat recovery method in a fuel cell power generation system according to claim 7 is based on the invention of claim 1 and is characterized by a cooling process in which heat generated from a fuel cell body is absorbed by cell cooling water, A pressurizing process of pressurizing to circulate cooling water, and a heat exchange process of recovering exhaust heat from the battery cooling water to a heat medium,
In the exhaust heat recovery method in a fuel cell power generation system including the above, the cooling process and the heat exchange process are performed without flow of the battery cooling water and the heat medium, and the heat exchange process is performed by the pressurizing process. It is performed on the battery cooling water after pressurization.
According to the first and seventh aspects of the present invention, there is no flow of substances between the battery cooling water system as the primary system and the heat medium of the heat exchanger as the secondary system. Is not corroded. Therefore, a specially high-performance water treatment device is not required, and the cost is reduced. Further, since the heat exchanger is provided on the downstream side of the circulation pump, cavitation does not occur in the circulation pump due to the pressure loss of the heat exchanger.
For this reason, stable operation becomes possible, and the reliability of the system is improved.

According to a second aspect of the present invention, in the fuel cell power generation system according to the first aspect, a water treatment device for purifying battery cooling water partially branched from the battery cooling water system, and the water treatment device upstream of the water treatment device is provided. A second heat exchanger that transfers exhaust heat from the battery cooling water to the battery cooling water downstream of the water treatment device. According to the second aspect of the present invention, since exhaust heat is taken from the battery cooling water on the upstream side of the water treatment device, water can be sent to the water treatment device at a temperature lower than a predetermined temperature allowed by the performance of the water treatment device.
On the other hand, the destination of the exhaust heat on the upstream side is the purified battery cooling water, and the purified battery cooling water is returned to the battery cooling water system after reheating. For this reason, the temperature of the battery cooling water in the battery cooling water system and the temperature of the steam generated by exhaust heat recovery can be maintained at high temperatures, and the efficiency of exhaust heat recovery from the battery cooling water system can be maintained at a high level.

According to a third aspect of the present invention, in the fuel cell power generation system according to the second aspect, the battery cooling water purified by the water treatment device is returned to the downstream of the heat exchanger in the battery cooling water system. It is characterized by having such a configuration. According to the third aspect of the present invention, the battery cooling water purified by the water treatment apparatus is returned to the downstream of the heat exchanger instead of the downstream of the steam separator. Exhaust heat recovery efficiency in the vessel is maintained at a high level.

According to a fourth aspect of the present invention, in the fuel cell power generation system according to the first aspect, the exhaust heat of the burner combustion exhaust gas of the reformer is recovered to the battery cooling water partially branched from the battery cooling water. A third heat exchanger, and a steam separator for separating the two-phase flow battery cooling water into water and steam, and providing the separated water to the heat exchanger. The battery cooling water whose exhaust heat has been recovered by the heat exchanger is refluxed to the steam separator. The invention of claim 8 is based on the invention of claim 4 and is understood from the viewpoint of the method. In the method for recovering exhaust heat in the fuel cell power generation system according to claim 7, the exhaust heat of the burner combustion exhaust gas of the reformer is A second heat exchange process for recovering the battery cooling water partially branched from the battery cooling water in the heat exchange process, and separating the two-phase flow battery cooling water into water and steam; And a steam-water separation process for providing the heat-exchange process to the heat-exchange process, wherein the battery cooling water from which waste heat is recovered in the second heat-exchange process is supplied to the steam-water separation process. In the invention of claims 4 and 8, since the exhaust heat of the burner combustion exhaust gas is also recovered in a part of the battery cooling water and returned to the steam-water separator, and the amount of heat can be collectively recovered by the heat exchanger. Exhaust heat recovery efficiency is improved.

According to a fifth aspect of the present invention, in the fuel cell power generation system according to the fourth aspect, a branch position of the battery cooling water to the third heat exchanger is provided downstream of the heat exchanger. And In the invention of claim 5, the battery cooling water for recovering the exhaust heat of the burner exhaust gas is branched from the downstream of the heat exchanger, but the battery cooling water downstream of the heat exchanger has the lowest temperature in the battery cooling water system, The difference between the internal pressure of the steam separator and the saturation temperature is large. For this reason, it is possible to maximize the exhaust heat absorption from the burner combustion exhaust gas, and the exhaust heat recovery efficiency is improved.

According to a sixth aspect of the present invention, in the fuel cell power generation system according to the fourth aspect, the third heat exchanger uses, as cooling water, battery cooling water partially branched from the battery cooling water system. It is characterized by being installed in parallel with the transformer. According to the invention of claim 6, the third heat exchanger for recovering the exhaust heat of the burner exhaust gas is installed in parallel with the carbon monoxide converter, not downstream. For this reason, the flow rate of the battery cooling water can be increased, the heat recovery amount in the heat exchanger increases, and the steam efficiency increases.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a plurality of embodiments of the present invention will be specifically described with reference to the drawings.

[1. First Embodiment] (1) Configuration The first embodiment corresponds to claims 1 and 7,
FIG. 1 is a configuration diagram of the fuel cell power generation system according to the first embodiment. Note that the same members as those in the conventional example shown in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted. The first embodiment has a battery cooling water system and an exhaust heat recovery system similarly to the conventional example shown in FIG. 5, but a feature of the first embodiment is that the steam generator 10 That is, it is provided downstream.

That is, the battery cooling water system guides a two-phase flow of battery cooling water (primary cooling water) from the fuel cell main body 1 to the steam separator 2 and separates the battery cooling water separated here into a battery cooling water circulation pump. This is a circulation system which pressurizes at 3 and circulates through the steam generator 10 and the temperature adjusting heat exchanger 4 to the fuel cell 1. Further, the exhaust heat recovery system includes a heat medium (secondary cooling water) from which exhaust heat has been recovered by the steam generator 10 and an exhaust heat recovery device 7 and a pump
This is a circulation system that circulates through 9 to the steam generator 10.

A device for transmitting waste heat between these two circulation systems is a steam generator 10 (corresponding to a heat exchanger according to claim 1). In the first embodiment, this steam generator is used. 10 is a battery cooling water circulation pump 3 in the battery cooling water system.
(Corresponding to the circulation pump in claim 1). In the first embodiment, a part of the battery cooling water is branched from the downstream of the steam generator 10 and is returned to the downstream of the steam separator 2 via the water treatment device 8 and the pump 9. .

As the primary cooling water and the secondary cooling water, water is typically used, and in both cases, other types of heat medium are used depending on various conditions such as the type of the fuel cell and the operating temperature. Different types of heat medium may be used for the primary cooling water and the secondary cooling water.

(2) Function and Effect The first embodiment having the above configuration has the following function. That is, heat generated during power generation in the fuel cell main body 1 is recovered by heat exchange (cooling process according to claim 7) in which the battery cooling water passing through the battery cooling plate 1c is heated. The cooling water 2b separated by the water separator 2 is supplied to the battery cooling water circulation pump 3
Pressurized. Exhausted heat of the pressurized battery cooling water
In the steam generator 10 provided downstream of the pump 3,
The heat is transferred to the heat medium on the secondary side (heat exchange process according to claim 7), and the steam generated by this transfer is used in the exhaust heat recovery device 7. The battery cooling water whose exhaust heat has been recovered by the steam generator 10 is temperature-adjusted to the inlet temperature of the battery cooling plate 1c by the heat exchanger 4, and then guided again to the battery cooling plate 1c.

In this cycle, a pressure loss occurs in the steam generator 10, but in the first embodiment, the pump 3
Is located upstream of the steam generator 10, there is no danger that cavitation will occur in the pump due to pressure loss, and stable operation will be realized. This also means that the steam generator 10 having a large pressure loss can be provided. That is, a steam generator having a large pressure loss has a fine and long heat transfer tube, and is a heat exchanger having excellent heat exchange efficiency per unit volume. For this reason, it is possible to reduce the volume of the steam generator. Therefore, according to the first embodiment, excellent heat exchange efficiency and miniaturization of the system are achieved while achieving stable operation.

The battery cooling water partially branched from the downstream of the steam generator 10 is purified by the water treatment device 8 and then returned to the downstream of the steam separator 2 by pressurizing the pump 9. In addition, it is free to set a specific position of the steam generator 10 downstream of the pump 3.

[2. 2. Second Embodiment (1) Configuration The second embodiment corresponds to claims 2 and 3.
FIG. 2 shows the configuration of the second embodiment. The same members as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. The features of the second embodiment shown in FIG.
In addition to the features shown in the first embodiment, the water supply preheater 17
(Corresponding to the second heat exchanger in claim 2).

That is, the battery cooling water on the upstream side, which is sent to the water treatment device 8 for purification, is referred to as blow water.
Is a heat exchanger configured as a low-temperature heating side with the battery cooling water on the downstream side of the heat exchanger. The role of the feed water preheater 17 is to transfer exhaust heat of the upstream blow water to downstream battery cooling water that is purified and returned to the battery cooling water system. Note that, depending on the temperature of the water that can be treated by the water treatment device 8, a part of the battery cooling water may be directly sent to the water treatment device 8 without passing through the water supply preheater 17. Is shown by a broken line.

(2) Function and Effect In the second embodiment having the above-described configuration, the water supply preheater 17 converts the battery cooling water on the upstream side of the water treatment device 8 to the downstream side of the water treatment device 8. The exhaust heat is transmitted to the battery cooling water at the time. That is, the water supply to the water treatment device 8 needs to be, for example, 60 ° C. or less in view of the performance of the water treatment device 8, but since the exhaust heat is taken from the battery cooling water on the upstream side of the water treatment device 8, The water supply to the treatment device 8 can be at or below a predetermined temperature allowed by the performance of the water treatment device 8.

On the other hand, if the battery cooling water purified by the water treatment device 8 is returned to the battery cooling water system at a low temperature of 60 ° C. or less, it causes a decrease in the temperature of the battery cooling water. In this case, since the inlet temperature of the steam generator 10 is reduced, the temperature of the steam obtained as a result of the exhaust heat recovery is reduced, and the exhaust heat recovery efficiency is reduced.

On the other hand, in the second embodiment, the cooling water flowing back from the water treatment device 8 to the battery cooling water system is reheated by the exhaust heat of the blow water in the feed water preheater 17, and then cooled. It will be returned to the cooling water system. As a result, in the second embodiment, the temperature of the steam obtained in the exhaust heat recovery system is also maintained at a high temperature by preventing the temperature of the entire battery cooling water system from lowering, and the exhaust heat recovery efficiency is maintained at a high level. (Claim 2).

In particular, in the second embodiment, as shown in FIG. 2, the battery cooling water purified by the water treatment device 8 is returned to the downstream of the steam generator 10 instead of the downstream of the steam separator 2. Therefore, the inlet temperature of the steam generator 10 does not decrease. For this reason, the exhaust heat recovery efficiency in the steam generator 10 is maintained at a high level. The specific temperature of the steam obtained by the steam generator 10 depends on various conditions. For example, high-temperature steam of about 160 ° C. can be obtained.

[3. 3. Third Embodiment (1) Configuration The third embodiment corresponds to claims 4 to 6, and FIG. 3 shows the configuration of the third embodiment. Note that the same members as those in the above embodiments are denoted by the same reference numerals, and description thereof will be omitted. A feature of the third embodiment shown in FIG. 3 is that a burner exhaust gas heat recovery unit 18 is provided in parallel with a carbon monoxide converter 20 in addition to the configuration shown in the first and second embodiments. .

That is, the carbon monoxide converter 20 is a device for removing carbon monoxide from the exhaust gas generated from the fuel cell main body 1, and branches a part of the battery cooling water from the downstream of the steam generator 10 in the battery cooling water system. And used as cooling water. The battery cooling water used for cooling in the carbon monoxide converter 20 is returned to the steam separator 2.

The third embodiment has a reformer with a burner (not shown). Here, the reformer is a device that reforms fuel gas to obtain a reformed gas for power generation that is rich in hydrogen, and the burner performs reforming by burning residual hydrogen of the reformed gas after power generation. A combustion device that provides energy for reaction to a reformer.

The steam generator 1 in the battery cooling water system
The battery cooling water partially branched from the downstream of the steam / water separator 2 passes through the low-temperature heated side of the burner exhaust gas heat recovery unit 18 and the steam-water separator 2.
Is led to. The burner exhaust gas heat recovery device 18 is a device for recovering exhaust heat contained in the burner combustion exhaust gas discharged from the burner, and corresponds to a third heat exchanger according to claim 4. The burner combustion exhaust gas flows on the high temperature heating side (primary side) of the burner exhaust gas heat recovery unit 18. In addition, downstream of the steam generator 10 which branches the battery cooling water toward the burner exhaust gas heat recovery unit 18 (Claim 5), the temperature of the battery cooling water is the lowest in the battery cooling water system,
For example, it is about 140 ° C.

Such a burner exhaust gas heat recovery unit 18 comprises:
It is provided side by side, that is, in parallel with the carbon monoxide converter 20. When a carbon monoxide converter and a burner exhaust gas heat recovery unit are provided in a fuel cell power generation system, conventionally, a burner exhaust gas heat recovery unit is provided in series on the downstream side of the carbon monoxide converter.

(2) Function and Effect In the third embodiment having the above-described configuration, in the burner exhaust gas heat recovery unit 18, the burner combustion exhaust gas on the high-temperature heating side has a high temperature of, for example, about 450 ° C. For this reason, the battery cooling water on the low-temperature heated side is also heated to a high temperature (the second heat exchange process according to claim 8). The heated battery cooling water has a saturation temperature of the internal pressure of the steam separator 2, for example, about 180 ° C., or a high temperature such that a part thereof boils to form a two-phase flow. Then, the heated battery cooling water is returned to the steam separator to be separated into steam and water (the steam separation process according to claim 8), and the separated high-temperature water is steam-generated through the pump 3. The exhaust heat is sent to the vessel 10 and the exhaust heat is collected in the exhaust heat recovery system.

As described above, heat is recovered from the burner combustion exhaust gas by the branched battery cooling water and returned to the steam separator 2 so that the calorific value of the burner combustion exhaust gas can also be recovered by the steam generator 10. As a result, the exhaust heat recovery efficiency of the entire system is improved. In particular, in the third embodiment, the branch point from the battery cooling water is located downstream of the steam generator 10, which is the lowest temperature part (for example, about 140 ° C.) in the battery cooling water system (claim 5). Therefore, the difference between the temperature of the low-temperature heated medium flowing into the burner exhaust gas heat recovery unit 18 and the saturation temperature of the internal pressure of the steam separator 2 becomes large, and a large amount of heat can be recovered. The efficiency of exhaust heat recovery is improved.

Further, in the third embodiment, since the burner exhaust gas heat recovery unit 18 is installed in parallel with the carbon monoxide converter 20, the combined flow rate of the battery cooling water is increased as compared with the conventional case. As a result, the amount of exhaust heat recovered by the steam generator 10 increases, and the energy use efficiency of the entire system improves.

[4. Other Embodiments] The present invention
The present invention is not limited to the above embodiments, but includes other embodiments as exemplified below. For example, specific elements such as a fuel cell body, a heat exchanger, a circulation pump, a water treatment device, and the like, a component composition of battery cooling water and other heat medium, a specific arrangement of each component device, and a piping configuration are as follows. , Can be freely determined. Further, the second and third heat exchangers are not necessarily required, and the positions at which the battery cooling water is branched and refluxed can be changed, and the third heat exchanger is provided in series with the carbon monoxide converter. You can also.

The specific temperatures shown in the above embodiments are merely examples, and the temperature at each position in the system differs depending on the type of fuel cell and other system configurations. Further, the present invention can be applied to a conventional fuel cell power generation system by adding equipment and changing the system configuration. Therefore, by efficiently using steam having a high temperature level, the exhaust heat recovery efficiency can be improved. An excellent fuel cell power generation system can be realized easily and at low cost.

[0050]

As described above, according to the present invention,
Excess heat from the fuel cell operation can be indirectly recovered by a secondary heat medium separated from the cell cooling water system, so that the cost of water treatment is reduced. In addition, since the heat exchanger therefor is provided downstream of the circulation pump of the battery cooling water, cavitation is prevented and stable operation is possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a fuel cell power generation system of the present invention.

FIG. 2 is a configuration diagram showing a fuel cell power generation system according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a fuel cell power generation system according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram showing an example of a conventional fuel cell power generation system.

FIG. 5 is a configuration diagram showing another example of a conventional fuel cell power generation system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fuel cell main body 1a ... Fuel electrode 1b ... Air electrode 1c ... Battery cooling plate 2 ... Steam separator 3 ... Battery cooling water circulation pump 4 ... Temperature control heat exchanger 7 ... Exhaust heat recovery device 8, 28 ... Water treatment Apparatus 9 Circulating pump 10 Steam generator 17 Feed water preheater 18 Burner exhaust gas heat recovery unit 19 Circulating pump 20 Carbon monoxide converter

Claims (8)

[Claims] 1. A battery cooling water system for absorbing heat generated from a fuel cell body into battery cooling water, a circulation pump for circulating the battery cooling water, and a heat for recovering exhaust heat from the battery cooling water. A fuel cell power generation system comprising: a heat exchanger of the heat exchanger, wherein the heat exchanger is provided downstream of the circulation pump. Characteristic fuel cell power generation system. 2. A water treatment device for purifying battery cooling water partially branched from the battery cooling water system, and a battery cooling water upstream of the water treatment device.
2. The fuel cell power generation system according to claim 1, further comprising: a second heat exchanger that transfers exhaust heat to battery cooling water downstream of the water treatment device. 3. 3. The fuel cell according to claim 2, wherein the battery cooling water purified by the water treatment device is returned to the downstream of the heat exchanger in the battery cooling water system. Power generation system. 4. A third heat exchanger for recovering exhaust heat of the burner combustion exhaust gas of the reformer into battery cooling water partially branched from the battery cooling water, and a two-phase flow battery cooling water. And a steam-water separator for providing the separated water to the heat exchanger. The battery cooling water having the exhaust heat recovered by the third heat exchanger 2. The fuel cell power generation system according to claim 1, wherein the fuel cell power generation system is configured to return to the steam separator. 5. The fuel cell power generation system according to claim 4, wherein a branch point of the battery cooling water to the third heat exchanger is provided downstream of the heat exchanger. 6. The third heat exchanger is provided in parallel with a carbon monoxide converter that uses, as cooling water, battery cooling water that is partially branched from the battery cooling water system. The fuel cell power generation system as described in the above. 7. A cooling process for absorbing heat generated from the fuel cell main body into the battery cooling water, a pressurizing process for pressurizing the battery cooling water to circulate the battery cooling water, and using the exhaust heat from the battery cooling water as a heat medium. Heat exchange process for recovery;
In the exhaust heat recovery method in a fuel cell power generation system including the above, the cooling process and the heat exchange process are performed without flow of the battery cooling water and the heat medium, and the heat exchange process is performed by the pressurizing process. An exhaust heat recovery method for a fuel cell power generation system, wherein the method is performed on the pressurized cell cooling water. 8. A second heat exchange process for recovering exhaust heat of the burner combustion exhaust gas of the reformer into battery cooling water partially branched from the battery cooling water in the heat exchange process; A water-water separation process of separating the separated battery cooling water into water and steam, and providing the separated water to the heat exchange process. The battery cooling device recovers exhaust heat in the second heat exchange process. The exhaust heat recovery method for a fuel cell power generation system according to claim 7, wherein water is supplied to the steam-water separation process.