JPH0831435A - Method of adjusting cooling water temperature of fuel cell power generator - Google Patents

Abstract

(57) [Summary] [Purpose] The temperature of the cooling water is lowered when the operation is stopped to cool the fuel cell body to a safe low temperature of 100 ° C or less. A steam separator 21 that supplies cooling water to a fuel cell main body 1, introduces a heated and discharged two-phase flow to separate steam and water, and supplies a part of steam to a fuel reformer 11. And the reaction exhaust air from the fuel cell body 1 and the fuel reformer 1
1. A makeup water pipe 48 for replenishing the water vapor separator 21 with the produced water and a produced water collector 41 for collecting the water contained in the combustion exhaust gas from No. 1 and a cooling water for the water vapor separator 21. 41, a fuel cell power generator having a blowdown pipe 50 for sending to an air conditioner 41 is provided with an automatic opening / closing valve 61 in parallel with a throttle mechanism 49 of the blowdown pipe 50, which is opened when the operation is stopped, and a large amount of cooling water is separated into a steam separator The fuel cell main body is cooled by circulating the fuel cell main body 21 and the produced water collector 41 to a sufficiently low temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of adjusting the cooling water temperature of a fuel cell power generator for controlling the temperature of the fuel cell at the time of power generation and stop.

[0002]

2. Description of the Related Art A phosphoric acid fuel cell uses phosphoric acid as an electrolytic solution and steam-reforms a raw fuel such as methane gas to obtain hydrogen in a fuel gas and oxygen in the air. To generate electric power by an electrochemical reaction.In a fuel cell power generator incorporating a phosphoric acid fuel cell, heat generated during power generation is removed by supplying cooling water,
The operating temperature of the fuel cell body is kept constant and the heat generated is recovered and used effectively.

Further, when reforming raw fuel into fuel gas, a method is adopted in which steam is added to the raw fuel to promote reforming with a catalyst in a fuel reforming device, but reforming is carried out constantly. It is necessary to constantly replenish the required amount of water vapor, and it is necessary to constantly replenish the water vapor supply device with water corresponding thereto. The water to be used needs to be highly pure water, and ion-exchanged water from which impurities have been removed by an ion-exchange type water treatment device is usually used. On the other hand, in the electrochemical reaction of the fuel cell, generated water is generated, and in the fuel reformer, combustion generated water is generated due to the combustion for heating as described later. Since there are few impurities, the load on the ion-exchange type water treatment device can be reduced by using these generated water as raw water to the fuel reformer. The method of collection is adopted.

FIG. 4 is a first example of a basic system diagram of a gas system and a cooling water system of a conventional fuel cell power generator of this type. In this figure, the fuel cell main body 1 is schematically shown. A phosphoric acid electrolyte layer (not shown) is sandwiched between a fuel electrode 2 and an air electrode 3 to form a unit cell, and each unit cell is stacked. It is configured by arranging a cooling plate 4 having a cooling pipe in the.

Raw fuel such as methane gas is supplied to the fuel supply circuit 8
The high-pressure steam supplied from the steam separator 21 described later through the steam supply circuit 10 is mixed by the ejector pump 9 and sent to the fuel reformer 7.
The fuel reformer 7 is heated by combustion of the off gas discharged from the fuel electrode 2 and sent through the off gas supply circuit 12 and the air supplied from the combustion air supply circuit 16 under the reforming catalyst, and is rich in hydrogen. After being reformed into the soda gas, it is supplied to the fuel electrode 2 of the fuel cell main body 1 through the reformed gas supply circuit 11 to cause an electrochemical reaction.

On the other hand, the reaction air is the reaction air supply circuit 14
Supplied to the air electrode 3 of the fuel cell main body 1 to cause an electrochemical reaction. Of the gas discharged after the electrochemical reaction has occurred in the fuel cell body 1, the off gas discharged from the fuel electrode 2 contains hydrogen that has not contributed to the electrochemical reaction. It is sent to the vessel 7 and used for combustion and heating. The exhaust gas containing water after combustion is sent to the produced water collector 41 through the combustion exhaust gas circuit 18, and the produced product water is recovered. On the other hand, the air discharged from the air electrode 3 contains water generated by the electrochemical reaction, and is sent to the produced water recovery unit 41 through the reaction air discharging circuit 15 in the same manner as the above combustion exhaust gas to generate power. The produced water is collected.

The cooling water from the steam separator 21 is sent to the cooling pipe provided on the cooling plate 4 of the fuel cell main body 1 through the cooling water circulation circuit 20 by the cooling water circulation pump 22. The discharged water, which is a two-phase flow of steam and water that cools the heat generated by power generation and has a high temperature by receiving the heat, is sent to the heat recovery heat exchanger 23 and then returned to the steam separator 21. ,
It is separated into steam and cooling water. The separated water vapor is
The fuel is reformed through the steam supply circuit 10, and the cooling water is sent again to the cooling pipe provided on the cooling plate 4 of the fuel cell body 1. The cooling water reduced corresponding to the steam used for the fuel reforming is compensated by the makeup water sent through the ion exchange type water treatment device 47.

The heat recovery heat exchanger 23 is for recovering the heat stored in the high-temperature discharge water, and is a heat medium circulation circuit 2
The heat medium supplied in 5 is heat-exchanged with the high-temperature discharge water to raise the temperature and cool the discharge water, and at the same time, the heat is recovered to the outside for effective utilization. The heat recovery heat exchanger 23 is provided with a bypass pipe 26 and a three-way adjustment valve 27. By operating the three-way adjustment valve 27, the flow rates of the bypass pipe 26 and the heat recovery heat exchanger 23 are adjusted, The pressure of the steam separator 21, which is known by the pressure gauge 28, is controlled to be constant to suppress the fluctuation of the amount of steam sent from the steam separator 21 to the fuel reformer 7.

The produced water collector 4 supplied with the air exhausted from the air electrode 3 through the reaction air exhaust circuit 15 and the exhaust gas containing moisture after combustion from the combustion exhaust gas circuit 18.
In No. 1, these gases are cooled by directly contacting with the recovered water stored in the bottom portion, and circulated by the recovered water circulation pump 42, the recovered water cooler 43, and the nozzle 44 to recover each produced water. There is. The exhaust gas after collecting the generated water is
The gas is exhausted to the outside through the gas exhaust circuit 19.

A cooling water circuit 45 is incorporated in the recovered water cooler 43 to cool the recovered water and take out heat to the outside for effective use. On the other hand, the produced water collector 41
The recovered water stored in the bottom part of the water is supplied to the water vapor separator 21 via the ion exchange type water treatment device 47 by the make-up water pump 46 incorporated in the make-up water pipe 48, if necessary. As described above, it is used as make-up water for the cooling water reduced corresponding to the steam used for the fuel reforming.

Further, the water vapor separator 21 and the produced water collector 4
A blowdown pipe 50 equipped with a throttle mechanism 49 for adjusting the flow rate is installed between the blowdown pipe 1 and the nozzle 1. A part of the cooling water is sent from the water vapor separator 21 to the produced water recovery unit 41 through this pipe, is purified by the water treatment device 47 of the makeup water pipe 48, and is returned to the water vapor separator 21 again. Plays a role in maintaining a constant water quality.

As described above, in the conventional fuel cell power generator, the two-phase flow discharge water discharged from the cooling pipe of the cooling plate 4 of the fuel cell body 1 is separated into the steam and the cooling water by the steam separator 21. The separated steam is sent to the ejector pump through the steam supply circuit 10 and mixed with the raw fuel for fuel reforming. However, when the pressure of the steam separator 21 changes, the amount of steam supplied to the ejector pump changes. Therefore, since the mixing ratio of the steam and the raw fuel fluctuates or the pressure of the fuel gas fluctuates, the composition and the pressure of the reformed gas sent to the fuel electrode 2 are also affected, and eventually the operation of the fuel cell. Fluctuations in conditions lead to shortening the life of the fuel cell. Therefore, it is necessary to keep the pressure of the steam separator 21 as constant as possible.

In the above fuel cell power generator, as described above, the heat recovery heat exchanger 23 is provided with the bypass pipe 26,
The three-way adjusting valve 27 is used to adjust the flow rate of the heat recovery heat exchanger 23 to keep the pressure of the steam separator 21 constant, but in this method, the amount of steam in the returning cooling water is increased or decreased. Since the pressure control is performed by the method described above, the responsiveness of the pressure change of the steam separator 21 to the movement of the three-way regulating valve 27 is slow, and the pressure fluctuation of the steam separator 21 is ± 0.
There is a difficulty that it is difficult to keep it below 05 [kg / cm ³ ].

FIG. 5 is a basic system diagram of a gas system and a cooling water system of a fuel cell power generator of a second conventional example, which is adopted as a method for solving the problems of the first conventional example.
Components having the same functions as those of the first conventional example shown in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted. The difference between the second conventional example and the first conventional example is that the return pipe of the cooling water circulation circuit 20 for cooling the fuel cell body 1 is connected to the vapor space of the water vapor separator 21 and the conventional heat Instead of the system composed of the heat recovery heat exchanger 23 and the three-way adjusting valve 27, a pressure adjusting valve 51 for adjusting the steam flow rate for the purpose of adjusting the pressure of the steam separator 21 and a heat connected to an external cooling device. Steam condenser 52 for exchanging heat with the medium circulation device 25
And a condensed water tank 53 which is connected to the steam condenser 52 only by piping, and a water supply pump 54 which feeds the stored liquid in the condensed water tank 53 to the water vapor separator 21 are connected in series through the piping. The exhaust heat recovery device is connected and a circulation circuit of steam condensed water is formed between the exhaust heat recovery device and the steam separator 21. The condensed water tank 53 is the produced water recovery unit 41.
It is connected to and is maintained at approximately atmospheric pressure.

With this configuration, when the pressure in the steam separator 21 deviates from the set value, the flow rate of steam from the steam separator 21 to the steam condenser 52 is changed by adjusting the opening degree of the pressure adjusting valve 51. As a result, the pressure of the water vapor separator 21 can be immediately returned to the set value, so that it is possible to adjust the pressure with a quick response as compared with the control method of the second conventional example.
Therefore, the pressure of the steam separator 21 is set to, for example, ± 0.05.
Since it can be controlled with accuracy of [kg / cm ³ ] or less, the amount of steam can be stably supplied to the fuel reformer 7, and a stable operation of the fuel cell power generator can be performed.

[0016]

On the other hand, in the fuel cell power generator, it is necessary to lower the temperature of the fuel cell main body to at least 100 ° C. or lower when the fuel cell power generator is stopped and safely stored. To do so, the cooling water that cools the fuel cell body is 1
The temperature must be sufficiently lower than 00 ° C. Second above
In the configuration of the conventional example, since the pressure of the steam separator is accurately controlled and the amount of steam can be stably supplied to the fuel reformer, a stable operation of the fuel cell power generator can be performed. When the temperature of 100 ° C decreases to 100 ° C, the amount of steam becomes very small, so even if the pressure control valve is opened, the amount of steam that flows into the steam condenser and is cooled and condensed remains at a very small amount.
The temperature of the retained water in the steam separator is adjusted to 10 by the steam condenser.
It is not possible to cool below 0 ° C. In addition, in the method of sending the retained water in the steam separator to the generated water recovery device by the blowdown pipe incorporating the throttling mechanism, cooling it, and returning it to the steam separator again by the makeup water pipe to cool it, Since the flow rate is limited to a small amount, the cooling descent rate can be kept low. Therefore, in this configuration example, the temperature of the retained water in the steam separator is set to 1
There is a problem that it is difficult to lower the temperature below 00 ° C. and it is substantially impossible to cool the fuel cell main body to 100 ° C. or less at a practical cooling descent rate.

The present invention has been made in consideration of the above problems, and an object thereof is to stably supply the amount of steam to the fuel reformer because the pressure fluctuation of the steam separator is minute as in the conventional case. In a fuel cell power generator that can be operated stably,
It is an object of the present invention to provide a method for adjusting the temperature of cooling water that can cool the fuel cell main body to 100 ° C. or lower.

[0018]

In order to solve the above problems, in the present invention, (1) cooling water is supplied to the fuel cell main body and steam is supplied to the fuel reformer to heat the fuel cell main body. A steam separator that introduces the discharged two-phase flow cooling discharge water to separate it into steam and water, reaction discharge air discharged from the air electrode of the fuel cell body, and combustion exhaust gas discharged from the fuel reformer. In a fuel cell power generator having a makeup water pipe for supplying the produced water of the produced water collector to the water vapor separator, the produced water collector collecting the water contained in the water vapor separator and the produced water. It connects with a collector via a valve, and when the operation of the fuel cell power generator is stopped, the valve is opened and closed to supply the cooling water in the steam separator to the generated water collector for cooling. The water vapor through the makeup water pipe. And adjusting the temperature of the cooling water in the steam separator by returning to the separator.

(2) Further, the valve is an automatic opening / closing valve, and is arranged in parallel with a throttle mechanism of a blowdown pipe for supplying the cooling water of the water vapor separator to the produced water recovery device in order to maintain the quality of the cooling water. Installed in the steam generator, the automatic on-off valve is closed during normal operation of the fuel cell power generator, and is connected only by the throttle mechanism, and when the operation is stopped, it is opened to cool the steam separator. The water temperature will be adjusted.

(3) Also, the valve is an automatic adjustment valve, is installed in the blow-down pipe, and the opening of the automatic adjustment valve is made relatively small during normal operation of the fuel cell power generator, thereby making it similar to the throttle mechanism. The operation is performed, and the temperature of the cooling water in the steam separator is adjusted by increasing the opening when the operation is stopped.

[0021]

[Operation] As described in (1) above, the steam separator and the produced water collector are connected via a valve, and by opening and closing this valve, the cooling water in the steam separator is supplied to the produced water collector. If the temperature of the cooling water is adjusted by cooling it and returning it to the water vapor separator through the makeup water pipe, a large amount of cooling water was set to, for example, about 50 ° C. by increasing the opening of the valve. Since it is sent to the generated water collector and cooled, the cooling water in the steam separator can be quickly cooled by circulating it.
It will be cooled to a temperature sufficiently lower than 0 ° C.

Further, as described in (2) above, the valve is an automatic opening / closing valve and is installed in the blowdown pipe in parallel with the throttle mechanism, and the automatic opening / closing valve is closed during normal operation of the fuel cell power generator. In this case, the flow rate is limited because the flow is limited only by the throttle mechanism. Also, if the automatic on-off valve is opened when the operation is stopped, a large amount of cooling water in the steam separator will flow to the produced water collector through the automatic on-off valve with a relatively large opening. Therefore, it is cooled in the low-temperature produced water recovery unit to 100 ° C.
It will be cooled to a sufficiently lower temperature.

Further, as in the above (3), the valve is used as an automatic adjustment valve and installed in the blowdown pipe, and the opening of the automatic adjustment valve is set to the same degree as the throttle mechanism during normal operation of the fuel cell power generator. If the temperature is made relatively small and the opening degree is adjusted to be large when the operation is stopped, the temperature of the cooling water can be adjusted as in the case where the above-described automatic opening / closing valve is incorporated.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a gas system used in a first embodiment of a method for adjusting the cooling water temperature of a fuel cell power generator according to the present invention.
It is a basic system diagram of a cooling water system. The components having the same functions as those of the first conventional example shown in FIG. 4 or the second conventional example shown in FIG. The difference between this embodiment and the second conventional example is that the throttle mechanism 4 for adjusting the blowdown flow rate of the blowdown pipe 50 that connects the steam separator 21 and the produced water collector 41.
The automatic opening / closing valve 61 is installed in parallel with the switch 9.
When the operation of the fuel cell power generator is stopped, the automatic opening / closing valve 61 is opened and a large amount of cooling water is caused to flow through the blowdown pipe 50 to the produced water collector 41, and is returned to the steam separator 21 through the makeup water pipe 48 for circulation. By doing so, the cooling water is cooled to a temperature sufficiently lower than 100 ° C., and the temperature of the fuel cell main body 1 can be cooled to 100 ° C. or lower.

FIG. 2 is a basic system diagram of a gas system and a cooling water system used in the second embodiment of the method for adjusting the cooling water temperature of the fuel cell power generator according to the present invention. Components having the same functions as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted. The difference between this embodiment and the second conventional example is that only the automatic adjustment valve 62 is installed in the blowdown pipe 50 that connects the water vapor separator 21 and the produced water collector 41. During normal operation of the fuel cell power generator, the opening of the automatic adjustment valve is made relatively small so that it operates in the same manner as the throttle mechanism, and when the operation is stopped, the opening is increased to allow a large amount of cooling water to flow. Similar to the case of the first embodiment described above, the cooling water is cooled to a temperature sufficiently lower than 100 ° C.

In the above-described first and second embodiments, the steam separator 21 includes a pressure regulating valve 51, a steam condenser 52, a condensed water tank 53 and a water supply pump 54 for circulating condensed steam. Since the system is installed, the pressure of the steam separator 21 is accurately controlled by opening and closing the pressure adjusting valve 51, and the steam is stably supplied to the fuel reformer 7, as in the second conventional example. Therefore, the fuel cell power generator can be operated stably.

FIG. 3 is a basic system diagram of a gas system and a cooling water system used in the third embodiment of the method for adjusting the cooling water temperature of the fuel cell power generator according to the present invention. In the basic system of the present embodiment, the steam separator 21 is not provided with a steam condensed water circulation system including a pressure regulating valve 51, a steam condenser 52, a condensed water tank 53, and a water supply pump 54.
This is a difference from the basic system of the second embodiment.

In this configuration, when the fuel cell power generator is stopped, the automatic adjusting valve 6 is used as in the second embodiment.
By increasing the opening of 2 and flowing a large amount of cooling water, 1
It is cooled to a temperature well below 00 ° C. During normal operation, the cooling water is passed through the automatic adjusting valve 62 and the produced water collector 41
And a part of heat generated during power generation is recovered by the recovered water cooler 43. At this time, the automatic adjustment valve 62 plays the same role as the pressure adjustment valve 51 in the first and second embodiments. That is, the pressure of the water vapor separator 21 is monitored by the pressure gauge 28, and when the pressure becomes higher than the set value, the opening degree of the automatic adjustment valve 62 is increased to increase the flow rate of the cooling water sent to the produced water collector 41. When the pressure becomes lower than the set value, the automatic adjustment valve 62
The pressure of the steam separator 21 is adjusted by lowering the opening degree of and reducing the flow rate of the cooling water sent to the produced water recovery device 41. The system of this embodiment also has an advantage that the device to be incorporated is simplified and is inexpensive.

[0029]

According to the present invention, (1) cooling water is supplied to the fuel cell main body and steam is supplied to the fuel reformer, and the two-phase flow cooling exhaust water heated and discharged in the fuel cell main body is introduced. A water vapor separator for separating steam into water and a reaction water discharged from the air electrode of the fuel cell main body, and a produced water collector for collecting water contained in the combustion exhaust gas discharged from the fuel reformer. In a fuel cell power generation device having a makeup water pipe for supplying the generated water of the generated water collector to the steam separator, the steam separator and the generated water collector are connected via a valve, When the operation of the fuel cell power generator is stopped, the cooling water in the water vapor separator is supplied to the produced water collector to be cooled by opening and closing the valve, and then to the water vapor separator by the makeup water pipe. Inside the steam separator by returning Since the method of adjusting the temperature of the cooling water is adopted, the cooling water in the water vapor separator can be quickly cooled to 100 ° C. or less, and the fuel cell main body is surely cooled to the temperature at the time of stopped storage. I can do it now.

(2) Further, the valve is an automatic opening / closing valve provided in parallel with the throttle mechanism of the blowdown pipe for supplying the cooling water of the steam separator to the produced water recovery device, or the valve is A large amount of cooling water is provided by using the automatic adjustment valve provided in the blowdown pipe, and when the operation of the fuel cell power generator is stopped, the automatic opening / closing valve is opened or the opening of the automatic adjustment valve is increased. Since the cooling water is circulated between the water vapor separator and the produced water recovery device, the cooling water can be quickly cooled to 100 ° C. or less, and the fuel cell main body can be reliably brought to the temperature at the time of stop storage. You can now cool.

[Brief description of drawings]

FIG. 1 is a basic system diagram of a gas system and a cooling water system used in a first embodiment of a method for adjusting a cooling water temperature of a fuel cell power generator according to the present invention.

FIG. 2 is a basic system diagram of a gas system and a cooling water system used in a second embodiment of the method for adjusting the cooling water temperature of the fuel cell power generator according to the present invention.

FIG. 3 is a basic system diagram of a gas system and a cooling water system used in a third embodiment of the method for adjusting the cooling water temperature of the fuel cell power generator according to the present invention.

FIG. 4 is a basic system diagram of a gas system and a cooling water system showing a first conventional example of this type of fuel cell power generator.

FIG. 5 is a basic system diagram of a gas system and a cooling water system showing a second conventional example of this type of fuel cell power generator.

[Explanation of symbols]

 1 Fuel Cell Main Body 4 Cooling Plate 7 Fuel Reformer 9 Ejector Pump 10 Steam Supply Circuit 15 Reactive Air Discharge Circuit 18 Combustion Gas Discharge Circuit 19 Gas Exhaust Circuit 20 Cooling Water Circulation Circuit 21 Steam Separator 25 Heat Medium Circulation Circuit 41 Heated Water Recovery Circuit Device 43 Collected water cooler 46 Make-up water pump 47 Water treatment device 48 Make-up water pipe 49 Throttling mechanism 50 Blow-down pipe 51 Pressure adjusting valve 52 Steam condenser 53 Condensed water tank 61 Automatic opening / closing valve 62 Automatic adjusting valve

Claims (3)

[Claims] 1. Steam for supplying cooling water to a fuel cell main body and steam to a fuel reformer and introducing cooling exhaust water of a two-phase flow heated and discharged in the fuel cell main body to separate steam and water. A separator and a produced water collector that collects water contained in the reaction exhaust air discharged from the air electrode of the fuel cell body and the combustion exhaust gas discharged from the fuel reformer, and the generated water collector is generated. In a fuel cell power generator having a makeup water pipe for supplying water to the water vapor separator, the water vapor separator and the produced water collector are connected via a valve to stop the operation of the fuel cell power generator. At this time, by opening and closing the valve, the cooling water in the steam separator is supplied to the generated water recovery unit to be cooled, and the cooling water in the steam separator is returned to the steam separator by the makeup water pipe. Adjust the temperature of the cooling water Method of adjusting the cooling water temperature of the fuel cell power plant according to claim and. 2. An automatic valve provided in parallel with a throttling mechanism of a blowdown pipe for supplying cooling water from the steam separator to the produced water collector to maintain the water quality in the steam separator. An on-off valve.
A method for adjusting a cooling water temperature of a fuel cell power generator according to the description. 3. The valve is an automatic control valve provided in a blowdown pipe for supplying cooling water from the steam separator to the produced water recovery device in order to maintain the water quality in the steam separator. The method for adjusting the cooling water temperature of a fuel cell power generator according to claim 1.