JPH06176777A - Fuel cell power generation system - Google Patents

Abstract

PURPOSE:To stably control a fuel cell in a compact form, and to utilize high grade exhaust heat by connection supplying cell cooling water of a system to a heat utilizing unit outside of the cell, while the water is sealed and separated from the outside. CONSTITUTION:The separate flow of cell cooling water to an outside utilization unit 7a is controlled by adjusting the opening of control valves 9A, 9B, 9C, so that the temperature of a thermometer 10 at a point of confluence does not fall to a level of no more than a predetermined value. A cooler 4 is utilized when the temperature 10 is higher than the predetermined value. Since the cooling water is sealed in a system and a unit 7a without being released to atmospheric pressure, and is thus separated from the outside, the high grade water quality can be maintained once the two systems are flushed well. Since the quantity of heat of the cooling water is directly fed to the heat utilization unit outside, a steam generator is omitted, and compactness can be achieved for the entire system design.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a fuel cell power generation system for supplying both electric power and heat.

[0002]

2. Description of the Related Art A fuel cell power generation system includes a fuel cell body, a reformer for producing hydrogen gas from a fuel such as city gas or propane gas, an inverter device for converting direct current into alternating current, operation of the fuel cell body and hydrogen. A heat exchanger for maintaining the temperature of the working gas at a temperature suitable for generation, a cooling device for cooling the heat generation of the battery main body, a separator for separating the two-phase flow battery cooling water into reforming steam and battery cooling water Is a power generation system that converts the chemical energy of fuel such as city gas and propane gas into electric energy.

However, it is well accepted that the fuel cell power generation system is a highly efficient power generation system and has an excellent potential for heat utilization. Recently, in order to cope with environmental problems and to further exert the usefulness of a fuel cell power generation system, there has been a strong demand for its usefulness as a system for supplying electricity and heat, a so-called cogeneration system.

However, the conventional fuel cell power generation system is not necessarily satisfactory in that it effectively recovers exhaust heat and supplies high-quality heat energy (the high-quality heat energy here is referred to as "high-quality heat energy"). Is 160
Heat that has a high temperature drop such as steam above ℃). As an example of high-quality exhaust heat recovery in a conventional fuel cell power generation system, a heat recovery system in which high-temperature steam is directly taken out from a cell cooling water system is known.

FIG. 4 is a system diagram of a conventional example of a heat recovery system for directly taking out high temperature steam. In the figure, the fuel cell body 1
Includes a fuel electrode 1A, an air electrode 1B, and a battery cooling plate 1C that absorbs heat generated during power generation. The cooling water flowing through the battery cooling plate 1C is heated by the heat generated by the power generation of the battery main body 1 to become a two-phase flow of steam and water, and the water separated by the steam / water separator 2 at the downstream side is cooled by the primary cooling water system. It is sent again to the battery cooling plate 1C of the battery body 1 through the cooler 4 which cools the battery inlet temperature by the water circulation pump 3.

To cool the cooler 4, a suitable cold / hot fluid may be used on the secondary side 4A thereof. The heat carried away by the low-temperature refrigerant on the secondary side of the cooler 4 is generally recovered as low-grade heat energy.

The steam separated by the steam separator 2 is sent to a fuel reforming system (not shown) through the control valve 5 and used for reforming the main raw fuel. The surplus steam is supplied to the absorption type refrigerator 7b installed in the secondary cooling system through the control valve 6, and after driving the refrigerator 7b, the steam becomes condensed water, which is collected in the condensed water tank 12 and supplied by the water supply pump. 8 is sent to the inlet of the cooling water circulation pump 3 via the water treatment device 13. One end of the condensed water tank 12 is open to the atmospheric pressure.

The fuel cell power generation system produces hydrogen gas by chemically reacting fuel gas such as city gas and propane gas with steam in a reformer or the like, and takes out electric power from the electrochemical reaction of the hydrogen gas and air. ing. However, in the power generation system that directly takes out the steam of the steam separator 2 and uses it for exhaust heat, the steam amount required for the absorption refrigerator 7b changes depending on the operating condition of the absorption refrigerator 7b, while the steam separator At the same time, the steam supplied to the reformer is also taken out. Therefore, when the absorption refrigerating machine 7b is in an operating state requiring a large amount of steam, the pressure of steam supplied to the absorption refrigerating machine 7b,
It was difficult to control because the temperature decreased.

Also, the battery cooling water is taken out once,
After opening to atmospheric pressure, it is returned to the cooling system of the cell body again, so substances outside the fuel cell may mix into the cell cooling water, making it difficult to control the quality of the cell cooling water, and a high-performance water treatment device. I needed thirteen.

FIG. 6 is a system diagram of a conventional example by the conventional indirect vapor extraction method. As shown in the figure, a steam generator 11 is provided downstream of the steam / water separator 2 of the battery cooling water system,
High-quality exhaust heat is recovered from this steam generator 11.
9A, 9B and 9C are control valves and 10 is a thermometer.

In this indirect steam extraction method, the exhaust heat recovery steam and the reforming steam are taken out separately, and the steam generator 11 plays the role of a buffer tank. It has the advantage of being stable. Also, since the battery cooling water and the extracted steam are completely isolated,
There is an advantage that a water treatment device equivalent to a fuel cell power generation system that can easily control the water quality of battery cooling water and does not recover high-quality exhaust heat can be used. However, there is a drawback that a lot of space has to be allocated to the steam generator 11, and there is a drawback that the temperature and pressure of the taken-out steam are lowered by the pinch temperature of the steam generator 11.

FIG. 7 is a diagram of an exhaust heat recovery system of a conventional fuel cell power generation facility. In the same figure, in the exhaust heat recovery system of the fuel cell plant 20, the thermal energy recovered in the system is taken out in a vapor state. The absorption refrigerating machine 21 is used as cold heat. When the rated quantity of this refrigerating heat is used, the absorption refrigerating machine 21 is operated to recover the high temperature exhaust heat steam 2 in the system.
The entire heat energy of 2 is converted into cold heat, supplied to the cold heat utilization equipment 24 using the cold heat medium 23, and the waste heat generated in the absorption refrigerator 21 when converting the heat energy into cold heat is generated in the cooling tower 25. Dissipate to atmosphere.

When the demand for cold heat is reduced, for the purpose of balancing the heat balance of the fuel cell plant 20, a high temperature exhaust gas corresponding to the difference between the recovered exhaust heat amount at the time of rated cold heat demand and the actual utilization amount is used. The hot steam 22 is branched to the heat exchanger 27 installed in the system of the cooling tower 25 by using the flow rate control valve 26, and the high temperature exhaust heat steam 22 is cooled by using the heat medium 28 of the cooling tower 25.
By condensing, the thermal energy of the surplus high temperature exhaust heat steam 22 was dissipated to the atmosphere.

As described above, in the conventional exhaust heat recovery system of the fuel cell power generation facility, the cooling tower system of the absorption refrigerator has the heat exchanger for condensing the high temperature exhaust heat steam. Since such a heat exchanger is a steam condenser and tends to be a large-sized device, it has been desired to reduce the size of the device in a city-installed plant or the like where the installation area is strictly required.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and is compact, allows stable control of the fuel cell, and facilitates water quality control of the cell cooling water of the fuel cell. It is an object of the present invention to provide a fuel cell power generation system that does not require a high-capacity water treatment device, is capable of recovering high-quality exhaust heat, and has downsized devices such as heat exchangers. .

[0016]

In order to achieve the above object, the first aspect of the present invention provides a battery cell comprising a fuel electrode, an air electrode and an electrolyte, and a plurality of the battery cells are laminated and cooled. A fuel cell body in which a cooling plate that circulates a medium to absorb heat generated from the cell body is arranged between the stacks, a primary cooling system that circulates through the cell cooling plate, and a primary cooling system In a fuel cell power generation system including a gas-liquid separator that separates a cooling medium provided into a gas phase and a liquid phase, and a pump that circulates the cooling medium separated by the gas-liquid separator, the cooling medium of the primary cooling system The cooling medium in the liquid phase portion is connected to a heat utilization device outside the fuel cell.
According to claim 2 of the present invention, a fuel cell for generating power by introducing a fuel gas rich in hydrogen into the anode and air into the cathode, and thermal energy obtained in a vapor state from the working fluid in the plant. In a fuel cell power generation system that has an absorption chiller that converts heat into cold heat and a cold heat utilization system that consumes the cold heat obtained by this absorption chiller, the exhaust heat of the absorption chiller is dissipated to the atmosphere when using the cold heat. It is characterized in that it is configured to dissipate the surplus of the cooling heat energy of the cooling heat medium to the outside of the system to the cooling equipment such as a cooling tower or when the demand for the cooling heat is reduced.

[0017]

According to the first aspect of the present invention, the cell cooling water (primary system cooling water) of the fuel cell power generation system is sealed from the outside and is connected to the heat utilization equipment outside the fuel cell in an isolated state. Since it is configured, it is compact and can use high-quality waste heat. Further, in claim 2, since the equipment of the cooling tower at the time of utilizing cold energy is configured to be dissipated outside the system when the demand for cold energy is reduced, steady operation is possible without increasing the installation area of the plant. .

[0018]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a system diagram of an embodiment of the present invention. In the figure, control valves 9A, 9 are provided on the downstream side of the cooling water circulation pump 3.
B and 9C are provided, and a part (or all) of the battery cooling water
Is taken out of the fuel cell power generation system. The battery cooling water taken out to the outside is connected to the external heat utilization device 7a.
The battery cooling water is sealed and isolated from the outside, and the battery cooling water does not flow out to the outside and only the amount of heat is transferred to the external heat utilization device 7a.

In this fuel cell power generation system, the cell cooling water is the control valves 9A, 9A on the downstream side of the cooling water circulation pump 3.
A part (or all) of the cell cooling water is taken out from the fuel cell power generation system by B and 9C, and the heat amount is utilized by the external heat utilization device 7a. The cell cooling water, which has lost its heat and has decreased in temperature, returns to the fuel cell body again and joins with the cell cooling water of the fuel cell body. During this time, the battery cooling water is in a closed loop and is not opened to atmospheric pressure.

Next, the operation of this embodiment will be described.
In the present embodiment, by adjusting the opening degree of the control valves 9A, 9B, 9C, the split flow rate of the battery cooling water to the external heat utilization device 7a is controlled, and the temperature of the confluence (the temperature of the thermometer 10) is a predetermined battery. The temperature is controlled so that it does not drop below the inlet temperature. The cooler 4 is used when the temperature at the confluence is higher than a predetermined battery inlet temperature. Further, in the present embodiment, the battery cooling water is not released to the atmospheric pressure, is sealed in the two systems of the battery power generation system and the external heat utilization device 7a, and is isolated from other external environment. Therefore, after well flushing the battery cooling water system of the battery power generation system and the external heat utilization device 7a, the water quality of the battery cooling water can be kept high.

Further, in the conventional fuel cell power generation system,
While the heat quantity of the battery cooling water is once converted into steam and heat exchange is performed between the steam and the external heat utilizing equipment, in the present embodiment, the heat quantity of the battery cooling water is directly transferred to the external heat utilizing equipment. We are supplying. By combining the fuel cell body and the external heat utilization device in a complex manner, the steam generator is eliminated, and a compact design as a whole is possible.

FIG. 2 is a system diagram of another embodiment of the present invention. In the figure, control valves 9A, 9B and 9C are provided on the downstream side of the cooling water circulation pump 3, and a part (or all) of the cell cooling water is taken out from the fuel cell power generation system. The battery cooling water taken out to the outside is introduced into the refrigerator regenerator 14 that evaporates the refrigerant solution 15 of the absorption refrigerator such as sodium bromide or lithium bromide liquid.
The cell cooling water cooled by the regenerator 14 of the absorption chiller 7b returns to the fuel cell body again, merges with the cell cooling water of the fuel cell body, and is introduced into the inlet of the cooling plate 1C of the cell body 1. . A control valve 9A, 9B, 9C, a thermometer 10 for measuring the temperature after joining, and a cooler 4 are provided in the battery cooling water system. Even in this cooling water system, the battery cooling water is not opened to the atmospheric pressure and is sealed and isolated from the outside.

In this embodiment, a part (or all) of the cell cooling water is taken out of the fuel cell power generation system by the control valves 9A, 9B and 9C on the downstream side of the cooling water circulation pump 3 to perform absorption refrigeration. Refrigerant solution 15 of machine 7b
The refrigerant 16 of the absorption refrigerator, such as sodium bromide or lithium bromide liquid, is evaporated and concentrated and regenerated. The cell cooling water cooled by the regenerator 14 of the absorption chiller 7b returns to the fuel cell body again and joins with the cell cooling water of the fuel cell body.

Also in this embodiment, by adjusting the opening degree of the control valves 9A, 9B, 9C, the branching flow rate of the battery cooling water to the absorption refrigerator side is controlled, and the temperature at the confluence point (temperature of the thermometer 10) is controlled. The temperature is controlled so as not to drop below a predetermined battery inlet temperature. The cooler 4 is used when the temperature at the confluence is higher than a predetermined battery inlet temperature. Regenerator 1 of absorption refrigerator 7b
4 plays the role of a buffer tank, which enables stable control of the fuel cell power generation system. In addition, the battery cooling water is not released to atmospheric pressure, and the battery cooling water system is sealed in the two systems, the battery power generation system and the absorption refrigerator, and is in a state of being isolated from the outside world. Therefore, after thoroughly flushing the battery power generation system and the battery cooling water system of the absorption chiller, the water quality of the battery cooling water can be kept high.

FIG. 3 is a system diagram of still another embodiment of the present invention. As shown in the figure, the same effect can be obtained by controlling the split flow rate of the battery cooling water by using the three-way valve 9D instead of the control valves 9A and 9C. Further, the effect is the same even if another heat utilization device is used instead of the absorption refrigerator.

FIG. 4 is a system diagram of another embodiment of the present invention. As shown in the figure, when the rated amount of cold heat is used, the heat energy of the high temperature exhaust heat steam 22 extracted from the fuel cell plant 20 is converted into cold heat in the absorption refrigerator 21 and the cold heat medium 23 is used. And is supplied to the cold heat utilization equipment 24. The high-temperature exhaust heat steam 22 converts its thermal energy into cold heat via the absorption refrigerator 21.
Returned condensed water 29 is returned to the fuel cell plant 20.

When the demand for cold heat is reduced, the absorption chiller 21 is supplied with the high-temperature exhaust heat steam 22 corresponding to the cold heat demand rating. From the absorption refrigerator 21, a cold heat medium 23 having a temperature and a flow rate corresponding to the cold heat demand rating is obtained, but since the cold heat demand on the cold heat utilization equipment 24 side is reduced, a surplus of cold heat is generated. The flow path of the cold heat medium 23 corresponding to the excess cold heat is changed by the flow rate control valve 26 and is sent to the heat exchanger 30. Cold heat is absorption refrigerator 21
The temperature of the heat medium 28 is increased by removing the heat of the heat medium 28 sent from the heat exchanger 28, mixed with the return cold heat medium 23 from the cold heat utilization facility 24, and returned to the absorption refrigerator 21 again.

Here, the flow rate distribution between the cold heat medium 23 sent to the heat exchanger 30 and the amount sent to the cold heat utilization equipment 24 is
The mixed temperature of the returning cooling heat medium 23 from the heat exchanger 30 and the returning cooling heat medium 23 from the cooling heat utilization equipment 24 is measured by using the temperature measuring means 31 such as a thermocouple, and the signal is measured by the controller 3
In step 2, calculation / judgment is performed, and the opening degree of the flow rate control valve 26 is controlled to control the allocation of the cold heat medium 23 to the cold heat utilization equipment 24 and the heat exchanger 30.

[0029]

As described above, according to the first aspect of the present invention.
According to this, it is possible to provide a compact and low-cost fuel cell power generation system using high-grade exhaust heat, which does not require a steam generator or a large-capacity water treatment device. Further, according to claim 2 of the present invention, by installing a heat exchanger using a liquid for both the high temperature side fluid and the low temperature side fluid without installing a heat exchanger for condensing the high temperature exhaust heat steam, Even when the demand for cold heat is reduced, the plant can be operated steadily with almost no increase in the installation area of the plant.When the cold heat demand is reduced, the heat generated during operation of the absorption chiller is released to the atmosphere. It is possible to reduce the load on the equipment such as the cooling tower to be discharged. In the case of a cooling tower, it is possible to reduce the power consumption by incorporating control such as partially stopping the fan as the load decreases.

[Brief description of drawings]

FIG. 1 is a system diagram of an embodiment of the present invention.

FIG. 2 is a system diagram of another embodiment of the present invention.

FIG. 3 is a system diagram of still another embodiment of the present invention.

FIG. 4 is a system diagram of another embodiment of the present invention.

FIG. 5 is a system diagram of a conventional direct vapor extraction system.

FIG. 6 is a system diagram of a conventional indirect vapor extraction system.

FIG. 7 is a system diagram of an exhaust heat recovery system of a conventional fuel cell system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Battery main body, 1A ... Fuel electrode, 1B ... Air electrode, 1C ... Cooling plate, 2 ... Steam separator, 3 ... Cooling water circulation pump, 4 ... Cooler, 5, 6 ... Control valve, 7a ... Utilization of external heat Equipment, 7b ...
Absorption refrigerator, 8 ... Water supply pump, 9A, 9B, 9C ... Control valve, 10 ... Thermometer, 11 ... Steam generator, 12 ... Condensed water tank, 13 ... Water treatment device, 14 ... Refrigerator regenerator, 20
... Fuel cell plant, 21 ... Absorption refrigerator, 22 ... High temperature exhaust heat steam, 23 ... Cold heat medium, 24 ... Cold heat utilization equipment, 25
... cooling tower, 26 ... flow control valve, 27 ... heat exchanger (condenser), 30 ... heat exchanger, 31 ... temperature measuring means, 32 ...
Controller.

Claims (2)

[Claims] 1. A battery cell comprising a fuel electrode, an air electrode, and an electrolyte, and a plurality of layers of the battery cell, and a cooling plate for circulating a cooling medium to absorb heat generated from the battery body. A fuel cell body, a primary cooling system that circulates through the cell cooling plate, a gas-liquid separator that separates a cooling medium provided in the primary cooling system into a gas phase and a liquid phase, and In a fuel cell power generation system including a pump that circulates a cooling medium separated by a gas-liquid separator, the cooling medium in the liquid phase portion of the cooling medium of the primary cooling system is connected to a heat utilization device outside the fuel cell. And fuel cell power generation system. 2. A fuel gas rich in hydrogen is supplied to the anode,
A fuel cell that introduces air into the cathode to generate electricity, an absorption refrigerator that converts the heat energy obtained from the working fluid in the plant in the form of steam into cold heat, and the cold heat obtained by this absorption refrigerator In a fuel cell power generation system having a consuming cold heat utilization system, when the cold heat is used, it becomes a cooling device such as a cooling tower for dissipating the exhaust heat of the absorption chiller to the atmosphere, or when the demand for the cold heat is reduced. A fuel cell power generation system, characterized in that a surplus of cold energy of a cold heat medium is dissipated to the outside of the system.