JPH07142076A - Fuel cell power generation device - Google Patents

Abstract

PURPOSE:To supply stable high temperature steam to a high temperature exhaust heat utilizing equipment regardless of a plant operating condition. CONSTITUTION:A heat exchanger 15 exchanges heat between battery cooling water to be supplied to the cooling water inlet piping side and secondary side cooling water, and cools the battery cooling water to a necessary temperature. In a heat exchanger 21, a secondary side heat exchanger tube is arranged in a steam separator 2, and cooling water after heat is exchanged on the secondary side of the heat exchanger 15 is supplied to the secondary side heat exchanger tube of the heat exchanger 21, and high temperature steam generated by exchanging heat with steam in the steam separator 2 is supplied to a high temperature exhaust heat utilizing equipment 24, and utilized water is circulated and returned to the secondary side of the heat exchanger 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell power generator equipped with a heat utilization device.

[0002]

2. Description of the Related Art A fuel cell power generator is a device for converting the chemical energy of a fuel such as city gas or propane gas into electric energy, and produces hydrogen from the fuel cell body and fuel such as city gas or propane gas. It is composed of a reformer for generation, an AC / DC converter for converting DC current into AC, a heat exchanger for maintaining the temperature of the working gas at a temperature suitable for the operation of the fuel cell main body and hydrogen generation.

The fuel cell main body directly converts the binding energy of hydrogen gas produced by the reformer and oxygen in the air into electricity, but heat is also generated at that time. Further, the fuel cell power generator is being widely commercialized as a clean power generator having high power generation efficiency due to the power generation by a chemical reaction, a small amount of emission of air pollutants and a small noise.

In order to efficiently carry out the electrochemical reaction of the fuel cell body, it is necessary to keep the temperature of the fuel cell body at a constant temperature level, and the fuel cell body is cooled and maintained at an appropriate temperature by cooling water or the like. This fuel cell cooling water system is composed of a steam separator, a pump, a heat exchanger, and the like, and exhaust heat extracted from the heat exchanger is used for various purposes.

In the past, this exhaust heat was only taken out as hot water, but in recent years, with the expansion of the range of uses of the exhaust heat, there has been a strong demand for taking it out as steam.

As shown in FIG. 2, the thermal efficiency of power generation against the power generation load is about 40%. However, when all of the low temperature exhaust heat recovery at the hot water level and the high temperature exhaust heat recovery at the steam level are used, the total efficiency is 20%. % Or more. In this way, the fuel cell power generator can effectively use not only power generation but also exhaust heat outside the system. Of the exhaust heat, the high-temperature exhaust heat at the vapor level is used as the steam turbine drive source of the absorption refrigerator. Used for.

In this steam extraction method, a direct steam extraction method for directly extracting vaporized battery cooling water and heat exchange with the battery cooling water system are performed once, and water of a system different from the battery cooling water is converted into steam and then extracted. There is an indirect steam extraction method.

FIG. 3 is a conceptual diagram of a type that directly takes out steam, and fuel gas is supplied to the fuel electrode 1a of the fuel cell 1 and air is supplied to the air electrode 1b. The heat generated here is cooled by the battery cooling water in the cooling plate 1c, and in the steam separator 2 into which the battery cooling water is introduced, it is separated into steam and water, pressurized by the pump 3, and the heat exchanger 4 Is cooled to a predetermined temperature, and returns to the cooling plate 1c of the fuel cell 1. In addition, 5 has shown the preheater at the time of starting the fuel cell 1.

On the other hand, a part of the steam generated in the steam separator 2 is supplied from the steam pipe 6 to the exhaust heat utilization device 7 and is returned by the circulation pump 8 to the battery cooling water system.
In addition, the water used in the exhaust heat utilization device 7 is treated in the water treatment device 9 so as to join the battery cooling water system.

FIG. 4 is a conceptual diagram of the indirect steam extraction type.

First, the reformer 1 is connected to the fuel electrode 1a of the fuel cell 1.
The fuel gas is supplied from 2 and the air is supplied from the blower 13 to the air electrode 1b. The heat generated in the fuel cell 1 is cooled by the cell cooling water in the cooling plate 1c, and the steam separator 2
It is designed to flow into.

In the steam separator 2, it is separated into water and steam,
The steam is supplied to the inlet side of the reformer 12, and the water is supplied to the primary side of the heat exchanger 15 by the pump 3 and returns to the battery cooling water system. The pump 1 is connected to the secondary side of the heat exchanger 15.
Water is supplied by 6 and hot water that has exchanged heat with the battery cooling water is supplied to the exhaust heat utilization device 7 and used. The water used in the waste heat utilization device 7 is pumped through the heat exchanger 17 to the pump 1
6 returns to the heat exchanger 15, and on the secondary side of the heat exchanger 17, the cooling water is pumped by the pump 18 to the DHC cooling tower facility 19
It is circulated and supplied to.

[0013]

However, the above-mentioned conventional fuel cell power generator has the following various problems regarding utilization of exhaust heat.

First, in the apparatus for directly taking out steam described with reference to FIG. 3, the steam generated in the steam-water separator 2 is used for a reformer for producing fuel such as city gas and propane gas into hydrogen. If the amount of steam taken out fluctuates, the amount of steam supplied to the reformer will be affected by the fluctuation, and the amount of hydrogen produced will be affected as well, and the amount of power generated by the fuel cell itself will also be affected. When the amount of steam fluctuates, stable operation is difficult.

Further, since the battery cooling water system and the exhaust heat utilization system have the same piping system, the exhaust heat utilization device 7 needs to have the same reliability as that of the battery, and must be equipped with a leakage prevention measure and a water pollution prevention measure. There is a problem that the plant as a whole becomes large and the cost becomes high due to the upsizing and the capacity increase of the water treatment device 9.

Secondly, the heat exchanger 1 described with reference to FIG.
In the method of indirectly taking out the exhaust heat by the method of 5,
-14876 Publication, Fuel cell body cooling system (US IFC
In order to recover phosphoric acid in a fuel cell as described in (Application), it is necessary to lower the temperature at the outlet of the heat exchanger 15 to the phosphoric acid condensation temperature. In that case, as shown in FIG. 5, since it is necessary to lower the fuel cell inlet temperature to 165 ° C., the difference between the cell cooling water temperature and the steam temperature, that is, the pinch temperature difference ΔT is small, and the pressure and temperature required by the market are small. It is not possible to use steam that satisfies the above conditions, and effective exhaust heat cannot be used.

As a countermeasure against this, a method of controlling the fuel cell inlet cooling temperature by adding a heat exchanger (not shown) after the heat exchanger 15 is also available, but this is disadvantageous in terms of cost and space.

On the other hand, FIG. 6 shows a system in which a heat exchanger 20 for recovering exhaust heat is installed on the upstream side of the steam separator 2 to indirectly take out high temperature exhaust heat from the heat exchanger 20.

According to this method, high-temperature steam can be taken out, but the battery cooling water discharged from the cooling plate 1c of the fuel cell 1 is in a gas-liquid two-phase flow, and the amount of heat generated by the battery is reduced by fluctuations in the power generation load. When it changes, the gas-liquid mixing ratio of the battery cooling water changes, and the amount of high-temperature exhaust heat recovery fluctuates in an unstable manner, so there is a problem that stable extraction of high-temperature exhaust heat is difficult.

Thus, in the direct vapor extraction system,
There are difficulties such as stable operation due to fluctuations in the amount of steam taken out, disadvantages such as large size and cost increase.
In the method where a heat exchanger is installed upstream of the steam separator to indirectly take out steam, the instability of operation during load changes and the heat exchanger for phosphoric acid recovery reduce the battery cooling water. There is a problem that the temperature of the taken-out steam is lowered and the steam cannot be used sufficiently.

Therefore, an object of the present invention is to provide a fuel cell power generator capable of performing stable power generation operation and capable of supplying stable high temperature and high pressure steam to a heat utilization device.

[0022]

According to the present invention, cell cooling water is supplied to a cooling water inlet pipe side connected to a cooler in a fuel cell main body and the cell cooling water taken out from a cooling water outlet pipe is used as steam. A battery cooling water circulation system that supplies water to a water / water separator that separates into water and returns the water separated from this water / water separator to the cooling water inlet piping side, and heat utilization that uses surplus energy of this battery cooling water circulation system In a fuel cell power generator including a heat utilization system for supplying to equipment, heat exchange between the cell cooling water supplied to the cooling water inlet pipe side and the cooling water on the secondary side to bring the cell cooling water to a required temperature. A first heat exchanger for cooling and a second heat exchanger for arranging a heat transfer pipe on the secondary side in the steam separator are provided, and heat is generated on the secondary side of the first heat exchanger. Cooling water after replacement is supplied to the heat transfer tube on the secondary side of the second heat exchanger. And heat exchanged with the steam in the steam separator to form high temperature steam, which is supplied to the heat utilization facility, so that the used water circulates back to the secondary side of the first heat exchanger. In addition, the heat utilization system is formed.

[0023]

With the above structure, the battery cooling water supplied to the cooling water inlet pipe side and the cooling water on the secondary side are heat-exchanged by the first heat exchanger to cool the battery cooling water to a required temperature. Then, the cooling water that has undergone heat exchange on the secondary side of the first heat exchanger is supplied to the heat transfer tube on the secondary side of the second heat exchanger to exchange heat with the steam in the steam separator. The generated high temperature steam is supplied to the heat utilization equipment, and the used water circulates back to the secondary side of the first heat exchanger. Therefore, since the cell cooling water required by the fuel cell can be cooled to the required temperature by the first heat exchanger and supplied, the plant can be stably operated, while the first heat exchanger can be operated regardless of the operating condition of the plant. The cooling water after heat exchange on the secondary side is heat-exchanged with the steam in the steam separator in the second heat exchanger, and the high-temperature steam can be supplied to the heat utilization facility.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a fuel cell power generator showing an embodiment of the present invention, and the same reference numerals as those in FIG. 4 showing a conventional example indicate the same or corresponding portions.

In the figure, 21 is a heat exchanger arranged in the steam separator 2, and this heat exchanger 21 is cooled by a pump 25 from the secondary side of the heat exchanger 15 via a switching valve 22. The water and the steam in the steam separator 2 are heat-exchanged with each other, and the high-temperature high-pressure steam is supplied to the high-temperature exhaust heat utilization equipment 24 via the switching valve 23.

Reference numeral 26 is a cooling tower for cooling the secondary side cooling water of the heat exchanger 15 through the switching valves 22 and 23 when the high temperature exhaust heat utilization equipment 24 does not require steam. Reference numeral 27 is an operation control panel that switches between the switching valve 22 and the switching valve 23, and 28 is a check valve.

First, the fuel electrode 1a of the fuel cell 1 is supplied with fuel gas from the reformer 12 and the air electrode 1b is supplied with air from the blower 13, so that the heat generated in the fuel cell 1 is cooled by the cooling plate 1c. It is cooled by the battery cooling water supplied to.
At the outlet of the cooling plate 1c, the battery cooling water reaches about 180 ° C,
It flows into the steam separator 2 in a two-phase flow of steam and water.

In the steam separator 2, water and steam are separated,
The steam is used to generate hydrogen in the reformer 12, and the water is pressurized by the pump 3 and used to cool the cooling plate 1c via the heat exchanger 15. At this time, in the heat exchanger 15, the secondary cooling water is adjusted so as to lower the cooling water temperature to the phosphoric acid condensing temperature in order to recover the phosphoric acid in the fuel cell 1.

On the other hand, the secondary cooling water of the heat exchanger 15 leaves the heat exchanger 15 and is guided to the heat exchanger 21 in the steam separator 2 via the switching valve 22 and the switching valve 23. Through the high temperature exhaust heat utilization equipment 24. At this time, the switching valve 22 is switched to form a flow path from a to b and the switching valve 23 is switched to form a flow path from b to c by a signal from the operation panel 27. This high temperature exhaust heat utilization equipment 24
In, steam is used as a driving source for air conditioning and steam turbines. The steam discharged from the high-temperature waste heat utilization equipment 24 is pressurized by the pump 25 via the check valve 28 and circulated as secondary cooling water.

When the exhaust heat recovery is not required and the high temperature exhaust heat utilization equipment 24 is stopped, the switching valve 22 is switched by the signal from the operation panel 27 so that the flow path is formed from a to c. Then, the switching valve 23 is switched so that a flow path is formed from a to d. As a result, the secondary cooling water discharged from the heat exchanger 15 becomes the cooling tower 26.
Then, it is cooled and returned to the pump 25. Switching of the switching valve 22 and the switching valve 23 and ON / O of the cooling tower 26
The FF is automatically controlled by the operation panel 27 of the high temperature exhaust heat utilization equipment 24.

As described above, in the fuel cell having the phosphoric acid recovery function, it was difficult to take out the high temperature and high pressure steam.
By providing a heat exchanger in the steam separator to reheat the secondary cooling water, the requirement can be sufficiently satisfied. In addition, since steam is not directly taken out from the steam separator, fluctuations in plant operation due to the effects of power generation of the fuel cell body and fluctuations in the amount of steam to the reformer are avoided, and stable operation is avoided. And the reliability can be improved.

In this embodiment, the switching valve 22 uses a three-way valve and the switching valve 23 uses a four-way valve. However, the present invention is not limited to this, and a two-way valve or the like can be combined to perform the same switching as in the present embodiment. It can be a valve. Further, reheating by the reformer is possible not only by relying on the thermal energy of the steam separator but by the same idea.

[0034]

As described above, according to the present invention, cooling water after heat exchange on the secondary side of the first heat exchanger is supplied to the secondary side of the second heat exchanger to separate water from water. Since the heat in the reactor is reheat-exchanged, the generated high temperature steam can be reliably and stably supplied to the heat utilization equipment regardless of the plant operating conditions.

[Brief description of drawings]

FIG. 1 is a system diagram of a fuel cell power generator showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a power generation load and efficiency.

FIG. 3 is a system diagram of a conventional fuel cell power generation device of a direct steam extraction type.

FIG. 4 is a system diagram of a conventional fuel cell power generation device of indirect vapor extraction type.

FIG. 5 is an explanatory diagram showing a relationship between a heat transfer tube length and a cooling water temperature.

FIG. 6 is a system diagram of a conventional high temperature exhaust heat extraction type fuel cell power generator.

[Explanation of symbols]

 1 Fuel Cell 1a Fuel Electrode 1b Air Electrode 1c Cooling Plate 2 Steam Separator 3,25 Pump 12 Reformer 13 Blower 15,21 Heat Exchanger 22,23 Switching Valve 24 High Temperature Exhaust Heat Utilization Facility 26 Cooling Tower 27 Operation Panel 28 Check valve

Claims (3)

[Claims] 1. A gas-water separation for supplying battery cooling water to a cooling water inlet pipe side connected to a cooler in a fuel cell main body and separating the battery cooling water taken out from the cooling water outlet pipe into steam and water. Cooling water circulation system for supplying water to the reactor and returning the water separated from this steam / water separator to the side of the cooling water inlet pipe, and a heat utilization system for supplying heat utilization equipment using surplus energy of this battery cooling water circulation system. A fuel cell power generator comprising: a first heat exchanger for exchanging heat between the cell cooling water supplied to the cooling water inlet pipe side and the cooling water on the secondary side to cool the cell cooling water to a required temperature; A second heat exchanger having a secondary side heat transfer tube arranged in the steam separator, wherein the cooling water after heat exchange on the secondary side of the first heat exchanger is In the steam separator, which is supplied to the heat transfer pipe on the secondary side of the second heat exchanger, Forming the heat utilization system so that high temperature steam generated by heat exchange with air is supplied to the heat utilization equipment, and the used water circulates back to the secondary side of the first heat exchanger. A fuel cell power generator characterized by: 2. A bypass system that bypasses an inlet side and an outlet side of the secondary side of the second heat exchanger, and an inlet of the secondary side of the second heat exchanger when the heat utilization facility is used. Switch to the secondary system that connects the outlet side with the outlet side,
The fuel cell power generator according to claim 1, further comprising a switching valve that switches to the bypass system when the heat utilization facility is not in use. 3. A cooling tower for cooling the cooling water after heat exchange on the secondary side of the first heat exchanger supplied through the bypass system when switched to the bypass system by the switching valve. The fuel cell power generator according to claim 2, wherein the fuel cell power generator is added.