JPH044572A - Vapor generator of fuel cell power generation system - Google Patents

Abstract

PURPOSE:To prevent drop of the cell output due to increase in leak current by forming the arrangement two divided, i.e., a pressure water sump with a built-in heating means wherein a closed loop circulating line for cooling water is piped around to the fuel cell and a water vapor generating part in heat conductive coupling with the pressure water sump to which a partitioning is provided. CONSTITUTION:The configuration of a water vapor generator according to the present invention consists of two divided parts - i.e., a pressure water sump 18 with built-in heating means 9, wherein a closed loop circulating line 7 for cooling water is piped around to the fuel cell concerned 2, and a water vapor generating part 19 in heat conductive coupling with the pressure water sump 18. Therefore, the reserved water in this pressure water sump 18 circulating to the fuel cell 2 is isolated from the reserved water in the water vapor generating part 19, and eventual application of external turbulence to the system on the vapor generating part 19 side about the pressure or temp. or in the form of purity drop of pure water 8 does not directly influence the system on the pressure water sump 18 side. This allows stable maintenance of the fuel cell at a specified operating temp. while a water 8 with high purity is circulated around to the fuel cell 2. Thereby drop of the cell output due to increase in the leak current can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a water vapor generator for a fuel cell power generation system, which also serves as a cooling water source for a water-cooled fuel cell and is connected to a cooling water circulation line of the fuel cell.

[Prior Art] A pressurized water cooling system has been known as a cooling system for liquid-cooled fuel cells. This cooling method circulates pressurized pure water from the outside through a cooling plate built into the fuel cell cell stack, removes the heat generated by the fuel cell reaction to the outside of the system, and cools the fuel cell at a specified level. It is rated C to maintain an operating temperature of .

In addition, in this case, in a normal fuel cell power generation system 1°,
In order to recover and effectively utilize the heat generated by the fuel cell, a steam generator is connected to the cooling water circulation line of the fuel cell, and water is used as a heat medium, and the steam stored in the steam generator is used for the fuel gas reformer. It is used in steam and other cogeneration systems to improve the thermal efficiency of the entire power generation system.

FIG. 2 is a flow diagram of a fuel cell power generation system centered on the conventional steam generator described above.
2 is a steam reformer that reformes natural gas into hydrogen-rich fuel gas as a raw material; 2 is a fuel cell; 3 is a cooling plate incorporated in the cell stack of fuel cell 2; 4 is a steam generator; A circulation pump 5 is installed between the generator 4 and the cooling plate 3 of the fuel cell 2. A cooling water circulation line 7 including a heat exchanger 6 for heat recovery is piped.

Here, the steam generator 4 is a single pressure tank having a steam generation space in the upper part of the body, and inside the tank there is pure water 8.
The top of the tank is equipped with a steam supply valve 10° for extracting steam 8a to the outside and supplying it into the power generation system, and a pressure regulating valve 11 for controlling the internal pressure of the tank.

Note that 12 is a liquid level gauge in the tank, and 13 is a conductivity gauge for monitoring the purity of pure water 8. The steam generator 4 also includes a pure water treatment device 14. Pure water tank 15. A pure water supply system including a water supply pump 16 is connected.

With this configuration, when the fuel cell 2 is started, the steam generator 4
With pure water 8 at a predetermined water level being supplied to the pump, the pure water is circulated through the cooling plate 3 of the fuel cell 2 by the circulation pump 5 while heating the pure water 8 in the steam generator 4 to raise its temperature by heating the heater. , the temperature of the fuel cell 2 is preheated to a predetermined operating temperature (160 to 170° C. for phosphoric acid fuel cells).

After the fuel cell 2 starts generating electricity, the heat generated by the fuel cell 2 is radiated and removed by circulating cooling water to the heat exchanger 6 installed in the cooling water circulation line 7, while at the same time generating water vapor. Steam 8a generated in the vessel 4 is supplied to the inlet side of the reformer 1 through the steam supply valve 10 and mixed with natural gas. In addition, the generated water generated in the fuel cell due to the cell reaction is produced by guiding the exhaust air of the air electrode to the condenser 17 to condense it, and then returning the recovered water to the pure water supply system and passing it through the pure water treatment device 14. Purified water is stored in a pure water tank 5, and is supplied to the steam generator through a water supply pump 16 when the water level in the steam generator 4 drops. Note that during operation of the fuel cell 2, the pressure of the steam generator 4, that is, the saturation temperature of steam, is controlled by the valve opening of the pressure regulating valve 11, and the temperature and steam pressure of the pure water 8 are adjusted within a predetermined control range. That's what I do.

[Problem to be solved by the invention]

By the way, the conventional steam generator described above has the following problems.

(1) The temperature of the pure water 8 stored in the steam generator 4 changes depending on the internal pressure of the steam generator, that is, the saturation temperature of the steam 8a, and the temperature of the pure water determines the operating temperature of the fuel cell 2. and affect battery output. Therefore, for example, the start of supply of cold water to the heat recovery heat exchanger 6 installed in the cooling water circulation line 7 in FIG. When a disturbance is applied, the influence of that disturbance appears directly as a change in the cooling water temperature, and the operating temperature of the fuel cell changes.
This in turn causes the battery output to fluctuate. In addition, steam supply valve 1
0. When the opening degree of the pressure regulating valve 11 becomes large and the internal pressure of the steam generator 4 drops rapidly, the suction pressure of the circulation pump 5 in the cooling water circulation line 7 temporarily becomes below the allowable value, and the discharge flow rate decreases significantly. As a result, fuel cell 2
The temperature of the electrode rises abnormally, causing a situation that deteriorates the catalyst layer of the electrode.

(2) The cooling water that circulates through the cooling plate of the fuel cell must be highly purified water (high electrical resistance), and the electrical resistance will decrease if impurities are mixed into the pure water. Then, leakage current that short-circuits between single cells inside the fuel cell,
Alternatively, the leakage current between the battery and ground increases and the battery output decreases.

In view of this, in the configuration of a conventional steam generator, the cooling water circulation line 7 including the heat exchanger 6 for heat recovery, the pure water supply system including the pure water treatment device 14, etc. are all connected to a single pressure vessel. For example, if the piping on the cooling water side inside the heat exchanger 6 corrodes due to dissolved oxygen in the water, creating pinholes, or the purification function of the water purification device 14 deteriorates, This causes the purity of the cooling water that is circulated through the fuel cell to decrease, causing the problem of increased leakage current in the fuel cell.

(3) In the conventional piping system, the heat exchanger 6 for heat recovery is installed in the cooling water circulation line 7 separately from the steam generator 4, so the equipment cost including the piping system and the heat Preventive maintenance to prevent liquid leakage (ordering pinholes) from exchangers costs a lot of money.

The present invention has been made in consideration of the above points, and provides a steam generator for a fuel cell power generation system that can solve the conventional problems described above by improving the structure of the steam generator. With the goal.

[Means to solve the problem]

In order to solve the above problems, the present invention provides a pressurized water reservoir with a built-in heating means, which is connected to a fuel cell with a closed-loop cooling water circulation line, and a water vapor generator that is thermally connected to the pressurized water reservoir. The water vapor generator shall be constructed by dividing into two parts.

Furthermore, in the steam generator having the above configuration, in order to improve heat transfer between the pressurized water reservoir and the steam generation section, the pressurized water reservoir and the steam generation section may be thermally coupled via a heat pipe. In order to simplify the structure of the recovery system, the steam generator having the above structure can be constructed by incorporating a heat exchanger for heat recovery into the steam generation section.

[Effect]

With the above configuration, the pressurized water reservoir functions as a cooling water source for the fuel cell, and the purified water stored here is circulated between the fuel pond and the fuel pond through a closed loop cooling water circulation line. On the other hand, the steam generator functions as a steam separator with a steam generation space inside its tank body, and the steam generated here is supplied to the steam reformer and other cogeneration systems. Make-up water accompanying consumption is directly introduced into the steam generator. Furthermore, the two are isolated from each other so that water cannot mix with each other. Therefore, the pure water in the pressurized water reservoir used as cooling water for the fuel cell is directly affected by disturbances such as sudden pressure and temperature changes in the steam generator, as well as water pollution generated in the steam generator. Water can be circulated between the fuel cell and the fuel cell in a stable manner while maintaining high purity.

Further, the heat pipe arranged between the pressurized water reservoir and the steam generating section functions to transfer heat from the pressurized water reservoir to the steam generating section. Thereby, the recovered heat taken from the fuel cell can be efficiently transferred from the pressurized water reservoir to the steam generating section and removed.

Furthermore, industrial water or other water is passed through the heat exchanger built into the steam generation section from the outside to recover heat.
Effectively used in cogeneration systems, etc. By directly incorporating the heat exchanger for heat recovery into the steam generating section in this way, not only can connecting piping to the heat exchanger be omitted, but also heat loss due to heat radiation from the connecting piping can be eliminated.

〔Example〕

FIG. 1 is a flow diagram of a fuel cell power generation system together with the configuration of a steam generator according to an embodiment of the present invention.
Identical parts corresponding to the figures are given the same reference numerals.

That is, according to the present invention, the steam generator 4 is connected to the pressurized water reservoir section 1.
It is constructed by stacking two independent tanks 8 and 19 vertically, and a plurality of heat pipes 20 for heat transfer are installed across both tanks.

Further, a closed loop cooling water circulation line 7 including a circulation pump 5 is installed between the pressurized water reservoir 18 and the cooling plate 3 of the fuel cell 2 . On the other hand, the steam generating section 19
The steam supply valve 10. In addition to the pressure regulator 11, a heat exchanger 17 for heat recovery is built directly into the tank body. Furthermore, the water supply piping drawn out from the water supply pump 16 of the pure water supply system is connected to the pressurized water reservoir J8. and a branch connection to the steam generating section 19.

Next, the operation of the above configuration will be explained. First, make-up water supplied from the outside to the steam generator 4 is purified into high-purity pure water by the deionized water treatment device 14, and then passed through the water supply valves 22 and 23 by the water supply pump 16 to the pressurized water reservoir 18 and the steam generation section. Supply water to 19. In this case, the pressurized water reservoir 18 is filled with water leaving almost no residual space, and the steam generating section 19 is set to a predetermined water level at which the heat exchanger 17 is submerged, leaving a steam generating space in the upper part of the body. .

Next, when starting up the fuel cell 2, the pure water 8 stored in the pressurized water reservoir 18 is heated and heated by the heater 9, and the pure water 8 is supplied to the fuel cell 2 through the closed loop cooling water circulation line 7 by the circulation pump 5. Water is circulated through the cooling plate 3 of the fuel cell 2 to preheat the fuel cell 2 to a predetermined operating temperature. At the same time, the retained heat of the pure water 8 heated in the pressurized water storage section 18 is transferred to the steam generating section 19 via the partition wall 1 of the tank body and the heat pipe 20.
The heat is transferred to the pure water 8 stored here, and the temperature of the purified water 8 is increased. When the water stored in the steam generating section 19 rises to a saturation temperature corresponding to the pressure set by the pressure regulating valve 11, steam 8a is generated, and the steam is supplied to the reformer and others through the steam supply valve 10.

On the other hand, when the fuel cell 2 is operating, the heat exchanger 1 for heat recovery
Industrial water is passed from the outside to 7, and heat is recovered by a cogeneration system (not shown) or the like. As a result, the heat generated by the fuel cell 2 is removed from the fuel cell using the flowing water of the cooling water circulation line 7 as a heat medium, and further
8 to a steam generator 19 via a heat pipe 20, etc.
After the heat is transferred to the side, the heat is recovered by the heat exchanger 17 and effectively used in a cogeneration system or the like. In addition, the water produced by the cell reaction of the fuel cell 2 is collected as condensate in a water recovery device 24, purified to pure water, and then stored in a pure water tank 15.
Extraction of steam 8a (steam supply valve 1)
0. If the liquid level in the steam generating section 19 falls below the standard water level due to the amount extracted from the pressure regulating valve 11, the water supply pump 16
The heat exchanger 21 provided in the pressurized water reservoir section 18. Water supply valve 2
3, pure water is supplied to the steam generating section 19. The water stored in the pressurized water reservoir 18 is simply circulated through the closed-loop cooling water circulation line 7 between the cooling plate 3 of the fuel cell 2 and the amount of water does not decrease. There is no need to replenish pure water during fuel cell operation, except when cleaning the inside of the tank.

In addition, although the steam generator of the illustrated embodiment is shown as having a pressurized water reservoir and a steam generating section each constructed of independent tanks, one tank is separated by a middle partition between the steam generating section at the end and the pressurized water at the bottom. It is also possible to configure it by partitioning it into a reservoir section.

[Effect of the invention] The steam generator of the fuel cell power generation system according to the present invention has the following features:
Since it is configured as described above, the following effects are achieved.

(1) The steam generator is connected to a pressurized water reservoir with a built-in heating means and a closed-loop cooling water circulation line piped between it and the fuel cell. By configuring the pressurized water reservoir and the steam generator that are thermally coupled to each other, the water stored in the pressurized water reservoir and the water vapor generated in the steam generator can be circulated between the fuel cell and the water vapor. are isolated from each other and do not mix, so even if disturbances such as pressure, temperature, and deterioration in the purity of pure water are applied to the system on the steam generation side, the effects of these disturbances will not be directly affected by the system on the pressurized water reservoir side. It never reaches. Therefore, while highly purified water is circulated between the fuel cell and the fuel cell, the fuel cell can be stably maintained at a predetermined operating temperature and operated at high output.

(2) By adopting a heat pipe with high heat transfer efficiency as a heat transfer means between the pressurized water reservoir and the steam generation section,
High heat conductivity can be ensured between the pressurized water reservoir and the steam generator.

(3) In addition, by incorporating a heat exchanger for heat recovery into the steam generation section, the piping system can be simplified, and
Heat loss in the piping system can also be reduced and heat recovery efficiency can be improved.

[Brief explanation of drawings]

FIG. 1 is a flow diagram of a fuel cell power generation system shown together with a steam generator according to an embodiment of the present invention, and FIG. 2 is a flow diagram of a fuel cell power generation system including a steam generator of a conventional configuration. In the figure, 'L: tampering device, 2: fuel cell, 3: cooling plate, 4: steam generator, 5: cooling water circulation pump, 7;
Cooling water circulation line, 8: Pure water, 8a: Steam, 9: Pure water heater, 17: Heat recovery heat exchanger, 18: Pressurized water reservoir, 19. Steam generation part, 20: heat pipe. Guryo＼ ,″i

Claims (1)

[Scope of Claims] 1) A steam generator connected to a cooling water circulation line of a water-cooled fuel cell, comprising a pressurized water reservoir with a built-in heating means and a closed loop cooling water circulation line connected to the fuel cell; 1. A steam generator for a fuel cell power generation system, characterized in that the steam generator is divided into two parts, and a steam generating part is thermally connected to a pressurized water reservoir by partitioning the water vapor generating part. 2) The steam generator for a fuel cell power generation system according to claim 1, wherein the pressurized water reservoir and the steam generation section are thermally coupled via a heat pipe. 3) The steam generator for a fuel cell power generation system according to claim 1, wherein a heat exchanger for heat recovery is incorporated in the steam generation section.