JPH10334934A - Phosphate-type fuel cell power plant and exhaust heat recover method in phosphate-type fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phosphate-type fuel cell power plant of small size and low cost, in which heat and water can be recovered efficiently from exhaust gas. SOLUTION: Most of phosphorus oxide contained in exhaust gas is mixed with steam contained in gas by cooling in a partition type heat exchanger 20a upstream of an exhaust gas condensing heat exchanger 20, and then the resultant phosphate product adheres to the surface of a heating tube. Consequently, the phosphate product is rarely dissolved into a condensed recovery water to deteriorate a quality of water. In a direct contact type heat exchanger 20b positioned downstream, cooling water is brought into direct contact with the exhaust gas, so that high heat transferring/condensing characteristics can be achieved in comparison with the partition type heat exchanger, thereby miniaturizing the heat exchanger. Since it is unnecessary to use a heating tube or the like for a contact portion, providing an inexpensive exhaust gas condensing heat exchanger realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphoric acid type fuel cell power generation apparatus for performing power generation by a fuel cell and recovering exhaust heat from exhaust gas, and to an improvement in a method for recovering exhaust heat in a phosphoric acid type fuel cell. In particular, the present invention has been improved so as to recover waste heat with excellent efficiency while being inexpensive and compact.

[0002]

2. Description of the Related Art A fuel cell power generator converts the binding energy of hydrogen gas generated by a hydrogen generator and oxygen in the air directly into electric energy. In addition, it is evaluated as an environmentally friendly power generation system with low emission of air pollutants and low noise.

In general, in a fuel cell power generator, a hydrocarbon-based fuel such as city gas and water vapor are reformed into a gas containing hydrogen as a main component by a reformer and supplied to a fuel electrode of a fuel cell body.
On the other hand, air is supplied to the air electrode of the fuel cell body. Then, a direct current is obtained by causing a chemical reaction between the hydrogen of the fuel electrode and the oxygen of the air electrode via the electrolyte in the fuel cell body. Further, the fuel cell power generation device is a power generation plant in which resource utilization efficiency is improved as a whole system by collecting and effectively utilizing heat generated as a result of power generation and water generated as a result of a chemical reaction. Among these, a phosphoric acid type fuel cell power generator uses phosphoric acid as the electrolyte.

FIG. 8 is a diagram showing an example of a conventional phosphoric acid fuel cell power generator. In FIG. 8, the fuel cell body 1
Is a matrix 1a impregnated with phosphoric acid as an electrolyte.
Is sandwiched between a fuel electrode 1b to which fuel gas is supplied and an air electrode 1c to which air is supplied to form a unit cell,
It is configured by laminating a large number of these. In the fuel cell main body 1, power is directly generated by an electrochemical reaction between fuel gas and air.

In this example, a hydrocarbon-based fuel F such as city gas is mixed with reforming steam 3 supplied from a steam separator 2, guided to a reaction section 4 a of a reformer 4, and subjected to steam reforming. The hydrogen-rich reformed gas 5 is generated by the hydrogen reaction. The reformed gas 5 contains hydrogen as a main component, and is further purified in the carbon monoxide converter 6, and then guided to the fuel electrode 1b as a fuel gas.

On the other hand, the reaction air 7 is supplied to the air electrode 1c of the fuel cell main body 1 by an air supply device 8 such as a blower. At this time, the hydrogen in the reformed gas 5 reacts with the oxygen in the reaction air 7 in the fuel cell body 1 to generate power. In the fuel cell main body 1, reaction heat is generated at the same time as power generation. Therefore, a cooling plate 1 d is provided for the purpose of maintaining the temperature of the fuel cell main body at about 190 ° C., and the cooling plate 1 d is cooled by the battery cooling water 9.

By the way, unreacted hydrogen remains in the reformed gas 5 which has been reacted at the fuel electrode 1b of the fuel cell body 1. For this reason, the reformed gas 5 after the reaction is burned together with the combustion air 10 in the burner 4 b of the reformer 4, and is used as a heating source of the reaction section 4 a of the reformer 4. It is discharged from the reformer 4. Further, the reaction air 7 which has completed the reaction at the air electrode 1c of the fuel cell body 1
Is discharged as exhaust air 12 while retaining moisture generated by the electrochemical reaction, and merges with the combustion exhaust gas 11 to form an exhaust gas 13. In order to make effective use of heat energy and water in the plant system, exhaust gas condensation heat exchange is performed. To the vessel 14.

The exhaust gas condensing heat exchanger 14 is a heat exchanger for collecting exhaust heat and recovering water by condensing steam with respect to the exhaust gas. Generally, a shell-and-tube heat exchanger is used. . The shell and tube type heat exchanger is a partition type heat exchanger in which a plurality of heat transfer tubes are installed in a container. In the heat exchanger 14, secondary cooling water 15 flows as a cooling medium into a heat transfer tube that is a low-temperature side flow path. The space around the heat transfer tube is a high-temperature side flow passage, and the exhaust gas 13 flows through this space. Exhaust heat of the exhaust gas 13 is transmitted to the wall of the heat transfer tube and collected in the secondary cooling water 15, and the heated secondary cooling water 15 and its steam are converted into the exhaust heat utilizing heat exchanger 16.
Is supplied to the external hot water utilization equipment 17 via the. As the hot water utilization facility 17, for example, a cooling / heating facility, a large-scale bath, and the like can be considered.

Further, by lowering the temperature of the exhaust gas 13 by heat exchange by the heat exchanger 14, the water vapor contained in the exhaust gas 13 is condensed into condensed water 19 and collected in the water treatment device 18. The collected condensed and recovered water 19 is purified by an ion exchange resin or the like in the water treatment device 18, returned to the plant system again, reused as the reforming steam 3 and the battery cooling water 9, and circulated through the plant. As a result, water self-sustaining operation is achieved without replenishing water from outside the plant during the operation of the plant. This not only contributes to saving of water resources, but also prevents deterioration of water quality by reducing wastewater, It can also contribute to protection.

[0010]

However, in the conventional phosphoric acid type fuel cell power generator, a partition wall type heat exchanger is generally used as an exhaust gas condensing heat exchanger. This heat exchanger of the partition type is provided with a metal heat transfer tube or a heat transfer wall over the entire area to provide exhaust gas 13 and secondary cooling water 15.
And exhaust heat recovery by indirect heat conduction. When heat conduction is performed only indirectly as described above, there is a problem that it is difficult to improve heat transfer characteristics required for cooling the exhaust gas 13 and condensation performance for condensing water vapor in the exhaust gas. In addition, since the partition-type heat exchanger needs to use a metal heat transfer tube or heat transfer wall as a whole, there is a limit to the cost reduction.

In some rare cases, a direct contact type heat exchanger is used. This direct-contact type heat exchanger recovers moisture and heat by directly injecting secondary cooling water into exhaust gas and bringing the exhaust gas into direct contact with the secondary cooling water. However, this direct contact heat exchanger has a problem that water quality is deteriorated. That is, in the above-described partition type heat exchanger, phosphorus oxide present in the air electrode exhaust gas is condensed and attached as a phosphoric acid product on the metal surface. Few. On the other hand, in the direct contact type heat exchanger, almost all the phosphorus oxide in the air electrode exhaust gas is dissolved in the condensed water, so that the water quality of the condensed and recovered water 19 is deteriorated. As for the condensed and recovered water 19 whose water quality has deteriorated in this way, it is necessary to remove the dissolved phosphorus oxide. Therefore, a particularly high-performance water treatment device 18 is required. There is a problem that the operating cost is increased to shorten the life.

The present invention has been proposed to solve the problems of the prior art as described above, and its object is to effectively recover heat and moisture from exhaust gas, and to reduce the size and cost. An object of the present invention is to provide a phosphoric acid fuel cell power generator and a method for recovering exhaust heat in a phosphoric acid fuel cell.

More specifically, an object of the present invention is to provide a heat exchanger for condensing exhaust gas with two heat exchangers, a partition type and a direct contact type, to reduce deterioration of water quality due to phosphoric acid and to achieve high heat transfer. It is to obtain a condensation characteristic (claims 1 and 9). Another object of the present invention is to achieve effective exhaust heat recovery by recovering exhaust heat of exhaust gas from a reformer and an air electrode (claim 2).

It is another object of the present invention to effectively recover waste heat from cooling water recirculated in an exhaust gas condensing heat exchanger. Another object of the present invention is to prevent damage to the recirculation pump by preventing air from being mixed into the recirculation pump (claim 6).

[0015]

According to a first aspect of the present invention, there is provided a phosphoric acid type fuel cell power generator for recovering exhaust heat of exhaust gas discharged from a fuel cell into cooling water. A first heat exchange section comprising an exchanger, wherein the heat exchanger partitions exhaust gas and cooling water to perform indirect heat conduction;
A second heat exchange unit provided on the downstream side of the exhaust gas with respect to the first heat exchange unit and for collecting exhaust heat by direct contact between the exhaust gas and the cooling water. Further, the exhaust heat recovery method for a phosphoric acid type fuel cell according to claim 9 is based on the invention of claim 1 from the viewpoint of the method, and the exhaust heat of exhaust gas discharged from the fuel cell is converted into cooling water. A heat exchange process for recovering, the heat exchange process comprising: a first process for recovering waste heat by indirect heat conduction separating exhaust gas and cooling water; and a heat treatment process subsequent to the first treatment. And a second process for recovering exhaust heat by direct contact between the exhaust gas and the cooling water. According to the first and ninth aspects of the present invention, first, exhaust heat recovery by indirect heat conduction is performed on the upstream side of the exhaust gas. At this time, most of the phosphorus oxide in the exhaust gas is combined with the water vapor in the gas by cooling to form a phosphoric acid product, and the phosphoric acid product adheres to the surfaces of heat transfer tubes and heat transfer walls that separate the exhaust gas and the cooling water. I do. Therefore, the degree of dissolution in cooling water or condensed water during operation to deteriorate the water quality is small. Subsequently, on the downstream side, since the cooling water comes into direct contact with the exhaust gas, higher heat transfer / condensation characteristics are obtained than on the upstream side, and the heat exchanger can be downsized. Further, since it is not necessary to use a heat transfer tube, a heat transfer wall, or the like in the contact portion, the cost of exhaust heat recovery can be reduced.

According to a second aspect of the present invention, there is provided the phosphoric acid type fuel cell power generator according to the first aspect, wherein a fuel cell main body having a fuel electrode and an air electrode; And a burner that supplies energy for a reforming reaction to the reformer by burning exhaust gas from a fuel electrode, and the heat exchanger includes the air. It is characterized in that exhaust heat is recovered from air electrode exhaust gas discharged from the pole and combustion exhaust gas discharged from the burner. Most of the exhaust heat generated from the fuel cell is contained in the cathode exhaust gas from the cathode and the combustion exhaust gas from the burner. Therefore, claim 2
According to the invention, the exhaust heat can be effectively reused by recovering the exhaust heat from the cathode exhaust gas and the combustion exhaust gas. Specifically, first, the exhaust gas from the fuel electrode has exhaust heat generated by power generation, and further burns residual hydrogen with the burner of the reformer to be a combustion exhaust gas having exhaust heat also generated by combustion. If the exhaust heat is recovered from the combustion exhaust gas, both the exhaust heat from the power generation and the exhaust heat from the combustion can be effectively reused. Further, since the other part of the exhaust heat generated by the power generation is included in the exhaust gas from the air electrode, if the exhaust heat is also recovered from the exhaust gas from the air electrode, all the exhaust heat generated by the power generation can be effectively reused. .

According to a third aspect of the present invention, in the phosphoric acid fuel cell power generator according to the first aspect, the second heat exchanging part is
It has a contact area enlarging member for enlarging the contact area between the exhaust gas and the cooling water. According to the third aspect of the invention, the heat exchange performance per unit volume by the direct contact can be further enhanced by the contact area expanding member, and the heat exchanger for heat recovery and the heat exchange process can be further reduced in scale. And cost reduction.

According to a fourth aspect of the present invention, in the phosphoric acid fuel cell power generator according to the first aspect, the second heat exchange section is
A cooling water dispersing member for dispersing cooling water in exhaust gas is provided. In the invention of claim 4, since the gas-liquid contact area between the exhaust gas and the cooling water is increased by the cooling water dispersing member such as a perforated plate, the heat exchange performance per unit volume by direct contact can be further improved. Become. For this reason, the heat exchanger and the heat exchange process required for exhaust heat recovery can be further reduced in scale and cost.

According to a fifth aspect of the present invention, in the phosphoric acid fuel cell power generator according to the first aspect, the discharge port for taking out cooling water from the heat exchanger and the taken-out cooling water are circulated, whereby the cooling water is circulated. A recirculation pump for injecting as cooling water into the second heat exchange section, and by collecting exhaust heat of the taken out cooling water into the cooling water of the first heat exchange section before the injection, A second heat exchanger for cooling the cooling water taken out. According to a tenth aspect of the present invention, the invention of the fifth aspect is grasped from the viewpoint of a method. In the exhaust heat recovery method for a phosphoric acid type fuel cell according to the ninth aspect, the cooling water is supplied from the heat exchange process. A process for taking out the cooling water, circulating the taken-out cooling water, and a pressurizing process for feeding into the second process; and, prior to the feeding, discharging heat of the taken-out cooling water to the first process. A second heat exchange process for cooling the taken-out cooling water by collecting it in the cooling water used in the process of
It is characterized by including. According to the fifth and tenth aspects of the present invention, when the cooling water used for the direct contact on the downstream side is taken out, steam in the exhaust gas is condensed in the cooling water in addition to the exhaust heat contained in the exhaust gas. Contains condensed water. For this reason, by circulating and reusing the taken-out cooling water, the reuse rate of the cooling water is improved. Also,
Waste heat of the extracted cooling water is transferred to the cooling water used for indirect heat conduction on the upstream side. For this reason, by concentrating all the exhaust heat on the cooling water for indirect heat conduction, it becomes possible to collectively use the hot water using facilities or the like. Therefore, it is possible to effectively use the exhaust heat while reducing the size and cost of the heat exchanger and the heat exchange process for recovering the exhaust heat.

According to a sixth aspect of the present invention, in the phosphoric acid type fuel cell power generator according to the fifth aspect, a liquid reservoir for preventing air from entering the recirculation pump is provided at the outlet. A detecting device for detecting a liquid level in the section. According to the sixth aspect of the present invention, even if the taken out cooling water contains bubbles, the liquid reservoir is provided with an upward convex shape, so that the bubbles are collected in the liquid reservoir due to a difference in specific gravity from the cooling water. You. For this reason, it is possible to prevent cavitation due to air mixing in the recirculation pump and subsequent damage to the pump. Further, even when the amount of air in the liquid reservoir exceeds a certain limit, it is possible to take measures such as detecting the level of the liquid level with a detection device and issuing an alarm if the level is abnormal. In particular, if the detection device is linked with the control system of the power generation device, the power generation device can be automatically stopped before the air accumulated in the liquid reservoir flows into the pump, and safe operation can be ensured.

According to a seventh aspect of the present invention, in the phosphoric acid type fuel cell power generator according to the fifth aspect, downstream of the discharge port,
It is characterized in that a removing means for removing solid impurities is provided. According to the seventh aspect of the present invention, the removing means such as the sedimentation tank or the filter removes foreign matters such as dust and scale flowing into the heat exchanger and solid impurities such as phosphoric acid products generated in the heat exchanger from the cooling water. Remove. For this reason, solid impurities are prevented from flowing into the recirculation pump, and troubles such as failure and wear of the pump are prevented, so that the operating reliability of the phosphoric acid fuel cell power generator can be improved.

According to an eighth aspect of the present invention, in the phosphoric acid type fuel cell power generator according to the fifth aspect, the cooling water cooled by the second heat exchanger is sprayed to the first heat exchanger. It is characterized by having spraying means for washing. In the invention of claim 8, the taken-out cooling water is controlled by a gate valve or the like, and is sprayed at a desired timing onto a heat transfer tube or a heat transfer wall of the first heat exchange section, or sprinkled from above. Can be sprayed. As a result, the surface of the heat transfer tube of the first heat exchange section can be washed while the power generator is stopped or operating, and by removing the phosphoric acid product attached, the heat transfer characteristics can be improved. It is possible to suppress the decrease.

[0023]

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

[1. 1. First Embodiment (1) Configuration The first embodiment corresponds to claims 1, 2, and 9, and FIG. 1 shows a phosphoric acid fuel cell power generation according to the first embodiment. It is a figure showing an apparatus. In the drawing, the same members as those in FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted.

The phosphoric acid type fuel cell power generator according to the first embodiment has substantially the same configuration as the conventional example shown in FIG. 8, but as shown in FIG.
Is a partition type heat exchange unit 2 having a built-in heat transfer tube or heat transfer wall.
0a, and a cooling water injection type direct contact heat exchange unit 20b disposed downstream of the exhaust gas from the partition type heat exchange unit.

Among them, the exhaust gas condensing heat exchanger 20 corresponds to the heat exchanger of claim 1 and realizes the heat exchange process of claim 9. The partition type heat exchange unit 20a
It is a part that separates exhaust gas and cooling water and recovers exhaust heat by indirect heat conduction. In addition, as a heat transfer member for partitioning the exhaust gas and the cooling water, a desired type such as a heat transfer tube and a heat transfer wall can be freely combined and used. For example,
A thin heat transfer tube is provided in a zigzag manner throughout the container through which the exhaust gas 13 flows, and the secondary cooling water 15 flows through the heat transfer tube. The partition type heat exchange section 20a corresponds to the first heat exchange section described in claim 1 and the first heat exchange section described in claim 9.
Realize the process.

Further, the direct contact heat exchange section 20b recovers exhaust heat by direct contact of the exhaust gas with the cooling water. In the form of direct contact, desired forms such as spraying, dripping, and flowing can be freely combined. The direct contact heat exchange section 20b corresponds to the second heat exchange section described in claim 1 and realizes the second process described in claim 9.

(2) Function and Effect The first embodiment having the above configuration has the following function. That is, the reformed gas obtained by reforming the fuel gas by the reformer 4 is supplied to the fuel electrode 1b, and as a result of power generation, becomes exhaust gas from the fuel electrode. This exhaust gas is supplied with energy for a reforming reaction to the reformer 4 by burning the residual hydrogen by the burner 4b, and is discharged as a combustion exhaust gas 11. The reaction air provided to the air electrode 1c is also discharged as the air electrode exhaust gas 12 (exhausted air) as a result of the power generation.

The exhaust gas 12 from the cathode 1c of the fuel cell body 1 and the exhaust gas 11 from the reformer 4 merge into the exhaust gas 13 and flow into the exhaust gas condensing heat exchanger 20. The inflowing exhaust gas 13 is supplied to the partition type heat exchange unit 2 provided with a heat transfer tube through which the secondary cooling water 15 flows.
0a and the direct contact heat exchange section 20b into which the cooling water 21 is injected. During this time, the exhaust gas 13 is cooled by the secondary cooling water 15 and the cooling water 21, and if there is any excess in the exhaust gas from which water vapor has been condensed and recovered, the exhaust gas 13 is subjected to necessary purification, and then is discharged from the exhaust gas condensing heat exchanger to the plant. Released into the outside atmosphere. On the other hand, the direct contact heat exchange unit 20b
The cooling water 22 that has completed the heat exchange with the exhaust gas is taken out from the lower part of the exhaust gas condensing heat exchanger 20, cooled, and supplied to the heat exchanger 20 again as the cooling water 21.

Incidentally, the exhaust gas 13 flowing into the exhaust gas condensing heat exchanger 20 contains phosphorus oxides diffused from the electrolyte of the fuel cell main body 1. Exhaust gas condensation heat exchanger 2
In the partition type heat exchange unit 20a located upstream of the exhaust gas 13, the exhaust gas 13 is cooled by the secondary cooling water 15, so that the phosphorus oxide in the exhaust gas 13 is combined with the water vapor in the gas to form phosphoric acid as phosphoric acid. It adheres to the heat transfer wall and the surface of the heat transfer tube in the exchange section and partially reacts with the material of the heat transfer tube such as stainless steel to generate a phosphoric acid product. The phosphoric acid product is mostly attached to the surface of the heat transfer tube. For this reason, the impurities in the condensed water 19 obtained by condensing the steam in the exhaust gas in the direct contact heat exchange section 20b are also reduced, so that the degree of deterioration of the water quality is reduced. The phosphoric acid product adhering to the heat transfer tube surface may be washed and removed at the time of periodic inspection of the power generator. As a result, the load on the water treatment apparatus is reduced, and a large-sized water treatment apparatus having a particularly high performance is not required. In addition, the reduction in the life of the ion exchange resin can be suppressed by the reduction in impurities, so that the cost of equipment and operation is reduced. In addition, since a simple and small water treatment device is sufficient, the size of the entire equipment can be reduced.

In the direct contact heat exchange section 20b located on the downstream side of the exhaust gas from the partition type heat exchange section 20a, the cooling water 21 injected into the heat exchanger directly contacts the exhaust gas 13, so Higher heat transfer / condensation characteristics can be obtained as compared with the heat exchange section, and the heat exchanger can be downsized. Further, since it is not necessary to use a heat transfer tube or the like for the direct contact heat exchange section 20b, an inexpensive exhaust gas condensation heat exchanger can be realized. The recovered waste heat is sent to the waste heat utilizing heat exchanger 16 in the form of steam of the cooling water 15 and is converted into hot water or steam having a temperature according to the purpose of use.
Used in 7

As described above, according to the first embodiment, the partition type heat exchange unit 20a and the direct contact type heat exchange unit 2
By using both Ob, it is possible to reduce equipment costs and operating costs, to reduce the size of the entire system, and to efficiently recover exhaust heat.

Most of the exhaust heat generated by the fuel cell is contained in the combustion exhaust gas from the burner and the air exhaust gas. Therefore, in the first embodiment, the exhaust heat can be effectively reused by recovering the exhaust heat from both the combustion exhaust gas and the air electrode exhaust gas. Specifically, first, the exhaust gas from the fuel electrode has exhaust heat generated by power generation, and further burns residual hydrogen with the burner of the reformer to be a combustion exhaust gas having exhaust heat also generated by combustion. In the first embodiment, since the exhaust heat is recovered from the flue gas,
Both waste heat from power generation and waste heat from combustion can be effectively reused. Further, the other part of the exhaust heat generated by the power generation is included in the exhaust gas from the air electrode. However, in the first embodiment, the exhaust heat is also recovered from the exhaust gas discharged from the air electrode. It can be reused in many ways. In the present application, the term “exhaust from the fuel cell” regarding the exhaust gas and exhaust heat means not only the exhaust gas and exhaust heat directly discharged from the fuel cell body, but also the exhaust gas and exhaust heat exhausted from attached devices such as burners. It is a broad concept that includes heat.

[2. Second Embodiment] FIG. 2 shows the configuration of a second embodiment of the present invention. The second embodiment corresponds to claim 3 and is similar to FIG.
Here, the same members as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

The feature of the second embodiment is that, in addition to the configuration shown in the first embodiment, an exhaust gas condensing heat exchanger 2
The contact area enlarging member 23 for increasing the gas-liquid contact area between the cooling water 21 and the exhaust gas 13 is provided inside the direct contact heat exchange unit 20b. The contact area enlarging member 23 can have a desired structure such as arranging multiple bar-shaped or fence-shaped members for transmitting cooling water to the surface. Further, it can be freely combined with a cooling water injection method such as water spraying or dripping, or can be used in combination with a structure in which the exhaust gas passage is formed in a folded shape to extend the distance.

As described above, if the area of the direct contact between the exhaust gas 13 and the cooling water 21 is increased, in proportion to the contact area,
Since the amount of heat conduction per unit volume increases, the heat exchange performance by direct contact can be further enhanced, and the exhaust gas condensation heat exchanger can be further downsized.

[3. Third Embodiment] FIG. 3 shows the configuration of a third embodiment of the present invention. The third embodiment corresponds to claim 4, and in FIG.
The same members as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

The feature of the third embodiment is that, in addition to the configuration shown in the first embodiment, the exhaust gas condensing heat exchanger 20
The cooling water dispersing member 24 is installed in the container of the direct contact heat exchange unit 20b. Although the specific structure of the cooling water dispersing member 24 is free, for example, the ceiling surface inside the container is covered with a perforated plate, and water droplets are dropped from each hole, or a sprinkler type watering device is provided or flows down. The cooling water can be freely determined, for example, by scattering the cooling water with a rotating body. In addition, the cooling water dispersing member 24 is desirably provided at an upper portion in the container, but not only at the upper portion,
For example, a sprinkler type may be provided on the side wall of the container. In the third embodiment, since the cooling water is dispersed, the gas-liquid contact area per unit volume between the exhaust gas 13 and the cooling water 21 increases, and thus, as in the second embodiment, The heat exchange performance by direct contact can be further enhanced, and the exhaust gas condensation heat exchanger can be further reduced in size.

[4. Fourth Embodiment] FIG. 4 shows the configuration of a fourth embodiment of the present invention. The fourth embodiment corresponds to claims 5 and 10, and in FIG. 4, the same members as those in FIGS. 1 and 8 are denoted by the same reference numerals, and description thereof will be omitted.

That is, in the fourth embodiment, the exhaust gas condensation heat exchanger 20 is provided with the recirculating water discharge port 25 for taking out the cooling water 22. This discharge port may be provided at the lower part of the container on the exhaust gas outlet side or the like. Further, a recirculation pump 26 for circulating the cooling water 22 taken out and injecting it as the cooling water 21 into the direct contact heat exchange unit 20b is provided. This recirculation pump 26 realizes the pressurizing process described in claim 10.

At the end of the recirculation pump 26, a cooling heat exchanger 27 is provided. The cooling heat exchanger 27 is used to cool the cooling water 22 by recovering waste heat of the cooling water 22 taken out from the exhaust gas condensing heat exchanger 20 into the secondary cooling water 15 of the fuel cell power generator. It is a heat exchanger. The cooling heat exchanger 27 corresponds to the second heat exchanger according to the fifth aspect, and realizes the second heat exchange process according to the tenth aspect.

The fourth embodiment having such a configuration has the following operation. That is, after being used for direct contact in the direct contact heat exchange unit 20b, in the taken-out cooling water 22, in addition to the exhaust heat contained in the exhaust gas 13, the steam in the exhaust gas 13 is condensed. Contains condensed water. Therefore, by circulating and reusing the taken out cooling water 22, the cooling water reuse rate is improved. The exhaust heat of the taken-out cooling water 22 is transmitted to the secondary cooling water 15 used for indirect heat conduction in the upstream-side partition-type heat exchange unit 20a. As described above, all the exhaust heat recovered from the exhaust gas 13 is concentrated in the secondary cooling water 15 and the steam generated from the secondary cooling water 15, and thus can be collectively used in the hot water utilization equipment 17 and the like. For this reason,
Effective utilization of exhaust heat is possible while reducing the size and cost of the heat exchanger and heat exchange process for exhaust heat recovery.

[5. Fifth Embodiment] FIG. 5 shows the configuration of a fifth embodiment of the present invention. The fifth embodiment corresponds to claim 6 and is similar to FIG.
The same members as those in FIGS. 4 and 8 are denoted by the same reference numerals, and description thereof will be omitted.

In the fifth embodiment, in addition to the configuration shown in the fourth embodiment, in order to prevent air from entering the recirculation pump 26, the recirculated water of the exhaust gas condensing heat exchanger 20 is used. A liquid reservoir 28 is provided at the discharge port 25 for discharge, and a detecting device 29 for detecting the level of the liquid level is provided. In addition, the liquid storage part 28 can be installed by providing an enlarged part in a part of the pipe, forming an upwardly convex dent, or providing a vertical pipe extending upward from a horizontal pipe. Further, the reservoir 28 may be provided with a valve or the like for releasing the accumulated air.

In the fifth embodiment, even if the taken out cooling water 22 contains bubbles, the liquid reservoir 2
Since the air bubbles 8 are provided, bubbles are collected in the liquid reservoir 28 by a difference in specific gravity from the cooling water 22. For this reason, it is possible to prevent cavitation due to air mixing into the recirculation pump 26 and subsequent damage to the pump 26. Further, even when the amount of air in the liquid reservoir 28 exceeds a certain limit, it is possible to take measures such as detecting an abnormal decrease in the liquid level with the detecting device 29 and issuing an alarm. In particular, if the detection device 29 is linked with the control system of the power generation device,
Before the air accumulated in the liquid reservoir 28 flows into the pump 26, the power generator is automatically stopped, and safe operation can be ensured.

[6. Sixth Embodiment] FIG. 6 shows the configuration of a sixth embodiment of the present invention. The sixth embodiment corresponds to claim 7, and in FIG.
4 and 8 are denoted by the same reference numerals, and description thereof will be omitted.

In the sixth embodiment, in addition to the structure shown in the fourth embodiment, the exhaust gas condensing heat exchanger 2
A removing means 30 such as a settling tank or a filter for removing solid impurities such as scale is provided downstream of the discharge port 25 for discharging the recirculated water. Accordingly, it is possible to prevent foreign matters such as dust and scale flowing into the exhaust gas condensing heat exchanger and phosphoric acid products generated in the exhaust gas condensing heat exchanger from flowing into the recirculation pump 26. Because of this, failures such as pump failure and wear are prevented,
The operation reliability of the phosphoric acid fuel cell power generator can be improved. The removing means is not limited to a precipitation layer or a filter, as long as it can remove solid impurities. Depending on the type of the solid impurities, a means based on another principle such as electromagnetic induction may be used.

[7. Seventh Embodiment] FIG. 7 shows the configuration of a seventh embodiment of the present invention. The seventh embodiment corresponds to claim 8, and in FIG.
4 and 8 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In the seventh embodiment, in addition to the configuration shown in the fourth embodiment, the cooling water 21 cooled by the secondary cooling water 15 in the cooling heat exchanger 27 is divided into a partition type heat exchange. A spraying means 32 for spraying the partition-type heat exchange section 20a through the gate valve 31 by spraying or sprinkling from above is provided for cleaning the section 20a. As the spraying means 32, any desired type such as a water faucet and a water discharge nozzle may be freely combined and used.

This makes it possible to clean the surfaces of the heat transfer tubes and the heat transfer walls of the partition type heat exchange section 20a of the exhaust gas condensing heat exchanger while the power generator is stopped or operating, and the phosphoric acid generation It is possible to remove the matter and to suppress a decrease in the heat transfer characteristics. In addition, since the cooled cooling water 21 can be sprayed, it can be used for temperature control when the partition-type heat exchange unit 20a is heated.

[8. Other Embodiments] The present invention is not limited to the above embodiments, but also includes other embodiments as exemplified below. For example, the configuration diagrams shown in FIGS. 1 to 7 are conceptual, and the specific arrangement of each device and the piping structure can be freely determined. Also, a contact area enlarging member 23 (FIG. 2), a cooling water dispersing member 24 (FIG. 3), a pipe including a recirculation pump 26 (FIG. 4) and a liquid reservoir 28 (FIG. 5), means for removing solid impurities 30 (FIG. 6) and means (FIG. 7) for sprinkling cooling water for cleaning are not limited in specific type, structure, type, and the like, and any desired one may be used. Also, a configuration including a recirculation pump 26 (FIG. 4) and a liquid reservoir 28 (FIG. 5) can be used simultaneously with the contact area enlarging member 23 (FIG. 2) or the cooling water dispersing member 24 (FIG. 3). It is. At the same time, means 30 (FIG. 6) for removing solid impurities,
A means for spraying cooling water for cleaning (FIG. 7) may be applied.

[0052]

As described above, according to the present invention,
Provided is a phosphoric acid fuel cell power generation device and a method for recovering waste heat in a phosphoric acid fuel cell, which are compact and low-cost and have excellent energy efficiency, because the load on the water treatment facility can be reduced and the effective exhaust heat recovery can be achieved at the same time. Can be.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a phosphoric acid fuel cell power generator according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of an exhaust gas condensing heat exchanger used in a phosphoric acid fuel cell power generator according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of an exhaust gas condensing heat exchanger used in a phosphoric acid fuel cell power generator according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a phosphoric acid fuel cell power generator according to a fourth embodiment of the present invention.

FIG. 5 is a configuration diagram of a phosphoric acid fuel cell power generator according to a fifth embodiment of the present invention.

FIG. 6 is a configuration diagram of a phosphoric acid fuel cell power generator according to a sixth embodiment of the present invention.

FIG. 7 is a configuration diagram of a phosphoric acid fuel cell power generator according to a seventh embodiment of the present invention.

FIG. 8 is a configuration diagram of a phosphoric acid fuel cell power generation device showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fuel cell main body 1a ... Matrix 1b ... Fuel electrode 1c ... Air electrode 1d ... Cooling plate 2 ... Steam separator 3 ... Reforming steam 4 ... Reformer 4a ... Reaction part 5 ... Reformed gas 6 ... Monoxide Carbon converter 7 ... Reaction air 8 ... Air supply device 9 ... Battery cooling water 10 ... Combustion air 11 ... Combustion exhaust gas 12 ... Exhaust air 13 ... Exhaust gas 14 ... Exhaust gas condensing heat exchanger 15 ... Secondary cooling water 16 ... Exhaust Heat utilization heat exchanger 17 Hot water utilization equipment 18 Water treatment device 19 Condensed and recovered water 20 Exhaust gas condensation heat exchanger 20a Partition wall heat exchange unit 20b Direct contact heat exchange unit 21 Cooling water 22 Discharge cooling Drainage 23 ... Contact area enlarging member 24 ... Cooling water dispersing member 25 ... Recirculating water outlet 26 ... Recirculating pump 27 ... Cooling heat exchanger 28 ... Liquid reservoir 29 ... Liquid level detecting device 30 ... Removal means 31 ... Gate valve 32 ... watering means

Claims (10)

[Claims] 1. A heat exchanger for collecting exhaust heat of exhaust gas discharged from a fuel cell into cooling water, wherein the heat exchanger partitions the exhaust gas and the cooling water to perform indirect heat conduction. A first heat exchange unit, a second heat exchange unit provided downstream of the exhaust gas with respect to the first heat exchange unit, and for collecting exhaust heat by direct contact between the exhaust gas and the cooling water; A phosphoric acid fuel cell power generator comprising: 2. A fuel cell body having a fuel electrode and an air electrode, a reformer for supplying a reformed gas obtained by reforming a fuel gas to the fuel electrode, and burning exhaust gas from the fuel electrode. And a burner for supplying energy for a reforming reaction to the reformer, wherein the heat exchanger is configured to discharge air exhaust gas discharged from the air electrode and combustion exhaust gas discharged from the burner. 2. The phosphoric acid fuel cell power generator according to claim 1, wherein the power is recovered. 3. The phosphoric acid fuel cell power generator according to claim 1, wherein the second heat exchange unit has a contact area enlarging member for enlarging a contact area between the exhaust gas and the cooling water. . 4. The phosphoric acid type fuel cell power generator according to claim 1, wherein the second heat exchange section has a cooling water dispersing member for dispersing the cooling water in the exhaust gas. 5. An exhaust port for taking out cooling water from the heat exchanger, and circulating the taken out cooling water, thereby forming the second cooling water.
A recirculation pump for injecting as cooling water into the heat exchange section; and collecting the exhaust heat of the taken out cooling water into the cooling water of the first heat exchange section before the injection, The phosphoric acid fuel cell power generator according to claim 1, further comprising: a second heat exchanger for cooling the cooling water. 6. A liquid reservoir for preventing air from entering the recirculation pump, and a detecting device for detecting a liquid level in the liquid reservoir at the discharge port. The phosphoric acid type fuel cell power generator according to claim 5, characterized in that: 7. The phosphoric acid fuel cell power generator according to claim 5, wherein a removing means for removing solid impurities is provided downstream of the outlet. 8. The phosphorus according to claim 5, further comprising a spraying unit for spraying the cooling water cooled by the second heat exchanger to the first heat exchange unit for washing. Acid fuel cell power generator. 9. A heat exchange process for collecting exhaust heat of exhaust gas discharged from the fuel cell into cooling water, wherein the heat exchange process is performed by indirect heat conduction that separates the exhaust gas and the cooling water. Exhaust heat recovery in a phosphoric acid fuel cell, comprising: a first process for recovering heat; and a second process for recovering exhaust heat by direct contact between exhaust gas and cooling water. Method. 10. A process for removing cooling water from the heat exchange process, and circulating the removed cooling water to form the second cooling water.
A pressurizing process for feeding into the process, and before the feeding, by collecting the exhaust heat of the cooling water taken out into the cooling water used in the first process,
The method according to claim 9, further comprising: a second heat exchange process for cooling the taken-out cooling water.