JP2002289242A - Fuel cell exhaust heat recovery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase recovered quantity of exhaust heat from a fuel cell. SOLUTION: A circulating pipe 5 is connected to a hot water storage tank 4, a cooling water circulating pipe 8 to supply cooling water is connected to a fuel cell main body 3, and a cooling water exhaust heat recovery heat exchanger 9 is provided between the cooling water circulating pipe 8 and the circulating pipe 5. A by-pass pipe 10 is provided in parallel with the cooling water exhaust heat recovery heat exchanger 9 on the cooling water circulating pipe 8, and a three-way valve 11 free to regulate a distributing flow rate is attached to a connecting point of the by-pass piping 10 and the cooling water circulating pipe 9. A sensible heat recovery heat exchanger 12 is provided on a piping part 8a on the side to supply to the cooling water exhaust heat recovery heat exchanger 9 between the connecting point with the by-pass pipe 10 of the cooling water circulating pipe 8 and the cooling water exhaust heat recovery heat exchanger 9, a latent heat recovery heat exchanger 13 is provided on a piping part 8b on the side to supply to the fuel cell main body 3, an exhaust gas pipe 14 from a reformer 2 is introduced to the latent heat recovery heat exchanger 13 through the sensible heat recovery heat exchanger 12, and even exhaust heat from the reformer 2 is recovered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell having a reformer and a fuel cell main body, which collects waste heat from a fuel cell which generates electricity and heat, and stores the waste heat in a hot water storage tank. The present invention relates to a fuel cell exhaust heat recovery system configured to be used for hot water supply and the like.

[0002]

2. Description of the Related Art As a conventional fuel cell exhaust heat recovery system, there is one shown in the system configuration diagram of a conventional example in FIG. That is, a cooling water circulation pipe 02 for supplying cooling water is connected to the fuel cell main body 01 of the fuel cell, and a circulation pipe 0 for circulating water to a hot water storage tank 03 for storing hot water.
4 and its circulation pipe 04 and cooling water circulation pipe 02
And a heat exchanger 05 is provided.

A bypass pipe 06 is provided in the cooling water circulation pipe 02 in parallel with the heat exchanger 05, and a three-way valve 07 capable of adjusting the distribution flow rate is provided at a connection point between the bypass pipe 06 and the cooling water circulation pipe 02. The flow rate of the cooling water flowing to the heat exchanger 05 side and the bypass pipe 06 side can be adjusted.

A cooling water temperature sensor 08 for measuring the temperature of the cooling water is provided at an inlet of the cooling water circulation pipe 02 to the fuel cell main body 01, and the cooling water temperature sensor 08 is provided.
Is connected to the first controller 09 and the first controller 09 is connected to the three-way valve 07 so that the temperature of the cooling water measured by the cooling water temperature sensor 08 is maintained at a set temperature (for example, 60 ° C.). The cooling control mechanism is configured to adjust the opening of the three-way valve 07.

A hot water temperature sensor 010 for measuring the temperature of hot water is provided at a location of hot water supply to the hot water storage tank 03 in the circulation pipe 04, and this hot water temperature sensor 010 is connected to a second controller 011. Second controller 01
1 is connected to a circulating pump 012 of variable discharge capacity provided in the circulating pipe 04 so as to maintain the temperature of the hot water measured by the hot water temperature sensor 010 at a set temperature (for example, 60 ° C.). The hot water storage temperature control mechanism is configured to adjust the discharge capacity of the hot water.

With this configuration, while maintaining the temperature of the cooling water to the fuel cell main body 01 constant, the heat of the cooling water after cooling the fuel cell is transferred to the water flowing through the circulation pipe 04 and collected as hot water at a set temperature. Then, the hot water is stored in the hot water storage tank 03 and can be used for hot water supply and the like.

[0007]

However, in the prior art, the temperature of the cooling water taken out of the fuel cell body 01 after cooling the fuel cell is about 65 ° C., whereas the cooling water supplied to the fuel cell body 01 is Must be maintained at 60 ° C., it is difficult to secure a sufficient amount of heat to be recovered as hot water in the hot water storage tank 03, and the amount of heat is insufficient when hot water supply demand is large.

The present invention has been made in view of such circumstances, and an object of the present invention is to increase the amount of exhaust heat recovered from a fuel cell. The invention according to claim 2 aims at effectively increasing the amount of exhaust heat recovered from the fuel cell, and the invention according to claim 3 sufficiently increases the amount of exhaust heat recovered from the fuel cell. The purpose is to be able to.

[0009]

According to the first aspect of the present invention,
In order to achieve the above object, a fuel cell having a reformer and a fuel cell main body to generate electricity and heat, a hot water tank for storing high-temperature hot water, and connected to the hot water tank A circulating pipe for circulating water, a cooling water circulating pipe for supplying cooling water to the fuel cell main body, and a cooling water circulating pipe provided between the circulating pipe and the cooling water circulating pipe to heat the cooling water after cooling the fuel cell. A cooling water exhaust heat recovery heat exchanger that transfers heat to water flowing through the circulation pipe; a bypass pipe provided in the cooling water circulation pipe in parallel with the cooling water exhaust heat recovery heat exchanger; a bypass pipe side and the cooling water; A valve mechanism for adjusting a flow rate of the cooling water flowing to the exhaust heat recovery heat exchanger side, and the valve for sensing a temperature of the cooling water supplied to the fuel cell body and maintaining the cooling water temperature at a set temperature. Fuel cell exhaust heat recovery system with a cooling control mechanism for controlling the mechanism A system is provided between the connection point of the cooling water circulation pipe with the bypass pipe and the cooling water exhaust heat recovery heat exchanger, from the cooling water exhaust heat recovery heat exchanger to the fuel cell main body. The cooling water is provided with a reformer exhaust heat recovery heat exchanger that transfers the exhaust heat of the gas exhausted from the reformer.

According to a second aspect of the present invention, there is provided a fuel cell exhaust heat recovery system according to the first aspect, wherein the reformer exhaust heat recovery heat exchanger comprises:
The latent heat recovery heat exchanger is configured to transfer and recover the latent heat generated by the condensation of the steam containing gas from the reformer.

According to a third aspect of the present invention, there is provided a fuel cell exhaust heat recovery system according to the second aspect of the present invention, wherein the cooling water circulating pipe is connected to the bypass pipe at a connection point with the bypass pipe. Between the cooling water exhaust heat recovery heat exchanger, the sensible heat of the gas discharged from the reformer is transferred to the cooling water supplied from the fuel cell body to the cooling water exhaust heat recovery heat exchanger. A sensible heat recovery heat exchanger for recovering and recovering the steam is provided, and the steam-containing gas after heat exchange in the sensible heat recovery heat exchanger is supplied to the latent heat recovery heat exchanger.

[0012]

According to the configuration of the fuel cell exhaust heat recovery system according to the first aspect of the present invention, the cooling water exhaust heat recovery heat exchanger discharges the cooling water supplied to the fuel cell body from the reformer. The fuel cell body that transfers the exhaust heat of the gas, raises the temperature of the cooling water supplied to the fuel cell body at the connection point between the cooling water circulation pipe and the bypass pipe on the supply side to the fuel cell body, and flows through the bypass pipe The amount of cooling water after cooling can be reduced.

[0013] Further, according to the configuration of the fuel cell exhaust heat recovery system according to the second aspect of the present invention, it is noted that the gas discharged from the reformer of the fuel cell contains steam.
After cooling the fuel cell main body, which transfers the latent heat accompanying the condensation of the water vapor-containing gas discharged from the reformer to the cooling water supplied from the cooling water exhaust heat recovery heat exchanger to the fuel cell main body and flows through a bypass pipe The amount of cooling water can be reduced.

Further, according to the configuration of the fuel cell exhaust heat recovery system according to the third aspect of the present invention, the fuel cell main body is located closer to the cooling water exhaust heat recovery heat exchanger than the connection of the cooling water circulation pipe to the bypass pipe. The sensible heat of the gas discharged from the reformer is transferred to the cooling water after cooling the fuel cell body, which is supplied to the cooling water exhaust heat recovery heat exchanger from the fuel, and the fuel is supplied to the cooling water exhaust heat recovery heat exchanger Raise the temperature of the cooling water after cooling the battery,
The amount of exhaust heat recovered as hot water in the hot water tank can be increased. In addition, the steam-containing gas after the heat exchange in the sensible heat recovery heat exchanger is supplied to the latent heat recovery heat exchanger to recover the latent heat.

[0015]

Next, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a system configuration diagram showing an embodiment of a fuel cell exhaust heat recovery system according to the present invention. FIG. 1 shows a polymer electrolyte fuel cell that generates electricity and heat. And a fuel cell main body 3.

Reference numeral 4 denotes a closed-type hot water tank for storing hot water. A circulation pipe 5 for circulating water from the lower part to the upper part is connected to the hot water tank 4, and a circulating pump P1 having a variable discharge capacity. Is provided, and is configured to store hot water in a state where temperature stratification is formed. In the figure, reference numeral 6 denotes a hot water supply pipe from which hot water is taken out, and reference numeral 7 denotes a water supply pipe for replenishing water for hot water supply. A cooling water circulating pipe 8 for supplying cooling water is connected to the fuel cell main body 3, and a cooling water circulating pump P 2 is interposed in the cooling water circulating pipe 8, and cooling water is provided between the cooling water circulating pipe 8 and the circulating pipe 5. An exhaust heat recovery heat exchanger 9 is provided.

A bypass pipe 10 is provided in the cooling water circulation pipe 8 in parallel with the cooling water exhaust heat recovery heat exchanger 9, and a distribution flow rate can be adjusted at a connection point between the bypass pipe 10 and the cooling water circulation pipe 9. A three-way valve 11 is provided so that the flow rate of the cooling water after cooling the fuel cell main body flowing to the cooling water exhaust heat recovery heat exchanger 9 side and the bypass pipe 10 side can be adjusted. According to the present invention, instead of the three-way valve 11, for example, a flow control valve is provided at each position of the bypass pipe 10 and the cooling water exhaust heat recovery heat exchanger 9 closer to the connection point between the bypass pipe 10 and the cooling water circulation pipe 9. The cooling water exhaust heat recovery heat exchanger 9 side and the bypass pipe 10
The flow rate of the cooling water after cooling the fuel cell main body flowing to the side may be adjusted, and these are collectively referred to as a valve mechanism.

Between the connection point of the cooling water circulation pipe 8 with the bypass pipe 10 and the cooling water exhaust heat recovery heat exchanger 9,
A sensible heat recovery heat exchanger 12 is provided in a pipe portion 8a supplied to the cooling water exhaust heat recovery heat exchanger 9, and a reformer exhaust heat recovery heat exchange is provided in a pipe portion 8b supplied to the fuel cell body 3. A latent heat recovery heat exchanger 13 is provided as a vessel.

The exhaust gas pipe 14 from the reformer 2 is introduced into the latent heat recovery heat exchanger 13 via the sensible heat recovery heat exchanger 12 and supplied from the fuel cell body 3 to the cooling water exhaust heat recovery heat exchanger 9. The sensible heat of the gas discharged from the reformer 2 is transferred and recovered to the cooling water after cooling the fuel cell body, and the latent heat of the steam-containing gas after heat exchange in the sensible heat recovery heat exchanger 12 is Cooling water exhaust heat recovery heat exchanger 9 to bypass pipe 10
It is configured to conduct heat to the cooling water supplied to the connection point with the cooling water and recover it.

A cooling water temperature sensor 15 for measuring the temperature of the cooling water is provided at an inlet of the cooling water to the fuel cell main body 3 in the cooling water circulation pipe 8, and the cooling water temperature sensor 15 is connected to the first controller 16. The first controller 16 is connected to the three-way valve 11 and connected to the three-way valve 11 to set the temperature of the cooling water measured by the cooling water temperature sensor 15 to a set temperature (for example,
The cooling control mechanism is configured to adjust the opening of the three-way valve 11 so as to maintain the temperature at 60 ° C.).

A hot water temperature sensor 17 for measuring the temperature of hot water is provided at a location of hot water supply to the hot water storage tank 4 of the circulation pipe 5, and the hot water temperature sensor 17 is connected to a second controller 18; The second controller 18 is connected to the circulation pump P1 and adjusts the discharge capacity of the circulation pump P1 so as to maintain the temperature of the hot water measured by the hot water temperature sensor 17 at a set temperature (for example, 65 ° C.). A hot-water storage temperature control mechanism is configured.

With the above configuration, while maintaining the temperature of the cooling water to the fuel cell main body 3 constant, the heat of the cooling water after cooling the fuel cell main body, the sensible heat of the gas discharged from the reformer 2 and The latent heat is transferred to the water flowing through the circulation pipe 5 and collected as hot water at a set temperature, and the hot water is stored in the hot water storage tank 4 and can be used for hot water supply or the like.

Next, a specific example of heat exchange of the above embodiment will be described. In the fuel cell 1 having a power generation capacity of 1 kW, the steam-containing exhaust gas (temperature 158 ° C.) from the reformer 2 is supplied from the sensible heat recovery heat exchanger 12 to the latent heat recovery heat exchanger 13 at a flow rate of 36 l / min. The heat recovery heat exchanger 12 transfers and recovers 100 W of heat, and the latent heat recovery heat exchanger 13 transfers and recovers 200 W of heat.

The heat output from the fuel cell body 3 is 943W,
When the temperature of the cooling water supplied to the fuel cell body 3 is set to 60 ° C., and the cooling water flows through the cooling water circulation pipe 8 so that the temperature of the cooling water after cooling the fuel cell body becomes 65 ° C., the cooling water flows to the bypass pipe 10. The flow rate was 2.32 l / min, and the flow rate to the cooling water exhaust heat recovery heat exchanger 9 was 0.38 l / min.

The cooling water after the cooling of the fuel cell main body having the above-mentioned temperature of 65 ° C. is passed through the sensible heat recovery heat exchanger 12 so that the temperature at the pipe portion 8 a supplied to the cooling water exhaust heat recovery heat exchanger 9 is increased. Could be raised to 69 ° C.

Then, by flowing water at a temperature of 20 ° C. through the circulation pipe 5 to the cooling water exhaust heat recovery heat exchanger 9 at 0.38 liters per minute, the 69 ° C. cooling water passed through the sensible heat recovery heat exchanger 12 The heat was exchanged, and hot water having a temperature of 65 ° C. was collected in the hot water storage tank 4. The temperature of the cooling water in the pipe portion 8b supplied from the cooling water exhaust heat recovery heat exchanger 9 to the fuel cell body 3 was 24 ° C. By flowing this cooling water through the latent heat recovery heat exchanger 13, the temperature of the cooling water could be raised to 32 ° C. At this time, the temperature of the steam-containing exhaust gas containing the drain passing through the latent heat recovery heat exchanger 13 was 30 ° C.

On the other hand, in the conventional system (see FIG. 2), the heat output from the fuel cell body 3 is 943 W, the temperature of the cooling water supplied to the fuel cell body 3 is 60 ° C., and the cooling water after cooling the fuel cell body is cooled. When the cooling water was passed through the cooling water circulation pipe 8 so that the temperature of the cooling water became 65 ° C., the flow rate flowing through the bypass pipe 10 was 2.37 l / min, and the flow rate flowing through the cooling water exhaust heat recovery heat exchanger 9 was 0.33 l / min. l. As in the example, a temperature of 20
When water at a temperature of 0.35 ° C. was passed through the cooling water exhaust heat recovery heat exchanger 9 at a rate of 0.33 l / min, heat exchanged with the cooling water at a temperature of 65 ° C. and the temperature of the hot water recovered in the hot water storage tank 4 was 60 ° C.

As a result, compared with the conventional system, the amount of exhaust heat recovered by the embodiment system can be reduced by the sensible heat recovery heat exchanger 1.
2 and the amount of heat recovered by the latent heat recovery heat exchanger 13 3
00W can be increased, and the ratio of the flow of the cooling water after cooling the fuel cell body to the exhaust heat recovery heat exchanger 9 can be increased.
It was clear that the temperature of the hot water recovered in the furnace could be increased by 5 ° C., and the exhaust heat recovery efficiency could be improved satisfactorily.

In the above embodiment, the connection point between the cooling water circulation pipe 8 and the bypass pipe 10 and the cooling water exhaust heat recovery heat exchanger 9
The sensible heat recovery heat exchanger 12 is provided in the pipe portion 8a supplied to the cooling water waste heat recovery heat exchanger 9, but depending on the temperature of the steam-containing gas discharged from the reformer 2, The sensible heat recovery heat exchanger 12 may not be provided, and the present invention includes an apparatus in which the sensible heat recovery heat exchanger 12 is not provided.

[0030]

As is apparent from the above description, according to the fuel cell exhaust heat recovery system according to the first aspect of the present invention, the exhaust heat of the gas discharged from the reformer is used to connect the cooling water circulation pipe At the connection point on the supply side to the fuel cell body with the bypass pipe, the temperature of the cooling water supplied to the fuel cell body is increased, and the amount of cooling water after cooling the fuel cell body flowing through the bypass pipe is reduced. The amount of cooling water after cooling the fuel cell main body supplied to the cooling water exhaust heat recovery heat exchanger can be increased, and the amount of exhaust heat recovered from the fuel cell can be increased.

Further, according to the configuration of the fuel cell exhaust heat recovery system according to the second aspect of the present invention, the latent heat of the steam-containing gas discharged from the reformer of the fuel cell due to the condensation of the steam is used to bypass the fuel cell. Since the amount of cooling water after cooling the fuel cell body flowing through the pipe is reduced, the amount of cooling water after cooling the fuel cell body to be supplied to the cooling water exhaust heat recovery heat exchanger can be increased, and the heat exhausted from the fuel cell can be increased. Can be effectively increased.

Further, according to the configuration of the fuel cell exhaust heat recovery system according to the third aspect of the present invention, not only the exhaust heat of the cooling water from the fuel cell body but also the water vapor content discharged from the reformer of the fuel cell. It collects not only the sensible heat of the exhaust gas but also the latent heat,
Cooling water waste heat recovery Not only can the amount of cooling water after cooling the fuel cell body supplied to the heat exchanger be increased, but also its temperature can be increased, and the amount of exhaust heat recovered from the fuel cell can be sufficiently increased . In addition, since the temperature of the cooling water after cooling the fuel cell body to be supplied to the cooling water exhaust heat recovery heat exchanger increases as well as the temperature of the cooling water, it can be applied even when the demand for hot water supply is high. There are advantages that can be improved.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing an embodiment of a fuel cell exhaust heat recovery system according to the present invention.

FIG. 2 is a system configuration diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fuel cell 2 ... Reformer 3 ... Fuel cell main body 4 ... Hot water storage tank 5 ... Circulation piping 8 ... Cooling water circulation piping 9 ... Cooling water waste heat recovery heat exchanger 10 ... Bypass piping 11 ... Three-way valve (valve mechanism) 12 … Sensible heat recovery heat exchange unit 13… Latent heat recovery heat exchange unit

Continued on the front page (72) Inventor Yoshitaka Kayahara 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi Inside Osaka Gas Co., Ltd. (72) Inventor Shin Iwata 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi Osaka Gas stock In-house F-term (reference) 5H026 AA06 CX06 5H027 AA06 BA01 CC06 DD06 KK28 KK48 MM16

Claims (3)

[Claims] 1. A fuel cell having a reformer and a fuel cell main body to generate electricity and heat, a hot water storage tank for storing hot water, and a circulation pipe connected to the hot water storage tank for circulating water. A cooling water circulating pipe for supplying cooling water to the fuel cell body; and a cooling water circulating pipe provided between the circulating pipe and the cooling water circulating pipe to transfer heat of the cooling water after fuel cell cooling to water flowing through the circulating pipe. A cooling water exhaust heat recovery heat exchanger that transfers heat; a bypass pipe provided in the cooling water circulation pipe in parallel with the cooling water exhaust heat recovery heat exchanger; a bypass pipe side and the cooling water exhaust heat recovery heat exchanger A valve mechanism for adjusting a flow rate of the cooling water flowing to the fuel cell body, and a cooling control for sensing the temperature of the cooling water supplied to the fuel cell main body and controlling the valve mechanism so as to maintain the cooling water temperature at a set temperature. Fuel cell exhaust heat recovery system Between the connection point of the cooling water circulation pipe with the bypass pipe and the cooling water exhaust heat recovery heat exchanger, the cooling water supplied from the cooling water exhaust heat recovery heat exchanger to the fuel cell body, A fuel cell exhaust heat recovery system comprising a reformer exhaust heat recovery heat exchanger for transferring the exhaust heat of the gas discharged from the reformer. 2. The fuel cell exhaust heat recovery system according to claim 1, wherein the reformer exhaust heat recovery heat exchanger transfers and recovers latent heat associated with the condensation of steam of the steam-containing gas from the reformer. Fuel cell exhaust heat recovery system, which is a latent heat recovery heat exchanger. 3. The fuel cell exhaust heat recovery system according to claim 2, wherein a portion of the cooling water circulation pipe connected to the bypass pipe and the cooling water exhaust heat recovery heat exchanger is connected to the fuel cell main body. A sensible heat recovery heat exchanger for transferring and recovering the sensible heat of the gas discharged from the reformer to the cooling water supplied to the cooling water exhaust heat recovery heat exchanger; A fuel cell exhaust heat recovery system configured to supply the steam-containing gas after heat exchange in step (1) to the latent heat recovery heat exchanger.