JP3695309B2 - Polymer electrolyte fuel cell system and operation method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polymer electrolyte fuel cell system that generates power using a polymer electrolyte fuel cell.
[0002]
[Prior art]
Hereinafter, a conventional polymer electrolyte fuel cell system will be described with reference to the drawings.
[0003]
FIG. 6 is a block diagram of a conventional polymer electrolyte fuel cell system. Pure water cooling water is supplied to a polymer electrolyte fuel cell 1 from a cooling water tank 2 through a cooling water channel 3 by a cooling water pump 4. The pure water cooling water that has passed through the fuel cell 1 constitutes a cooling water circulation system that returns to the cooling water tank 2 after being cooled by a heat exchanger 5 such as a radiator.
[0004]
At this time, conductive ions are dissolved in the pure water cooling water from the heat exchanger 5 that cools the cooling water, and if the conductive ions increase, there is a problem that a short circuit occurs in the fuel cell 1 and the power generation amount decreases. Therefore, it is necessary to remove conductive ions from the cooling water. For this reason, an ion removal filter 6 using an ion exchange resin for removing conductive ions dissolved from the heat exchanger 5 in the middle of the cooling water channel 3. Is provided.
[0005]
In addition, by installing the ion removal filter 6 on the cooling water channel 3, when the fuel cell 1 requires a large amount of cooling water in a high load operation, the pressure loss of the cooling water in the ion removal filter 6 increases. Therefore, the bypass path 7 for reducing the pressure loss is provided, and when using a small amount of cooling water that does not affect the pressure loss of the ion removal filter 6 in low load operation, the ion removal filter is used. 6 is provided on the bypass passage 7 with a flow rate control valve 8 through which pure water cooling water can be actively passed.
[0006]
[Problems to be solved by the invention]
The polymer electrolyte fuel cell system is usually operated by circulating cooling water at 70 to 80 ° C. Since the cooling water channel 3 of the polymer electrolyte fuel cell system shown in the above conventional example has a hermetic configuration, when the system is operated, the cooling water temperature changes from normal temperature cooling water before operation to high temperature cooling water during power generation. Accordingly, the pressure inside the cooling water tank 2 and the water pressure in the cooling water channel 3 rise. When the system operation is stopped, the cooling water temperature changes from the high-temperature cooling water during power generation to the normal temperature cooling water after the operation is completed, and the pressure inside the cooling water tank 2 and the water pressure in the cooling water channel 3 are lowered accordingly. Therefore, it is necessary to make the structure of the cooling water tank 2 and the cooling water channel 3 that can withstand pressure fluctuation due to temperature change.
[0007]
Further, since the ion removal filter 6 is in the cooling water channel 3, the amount of cooling water passing through the ion removal filter 6 increases as the flow rate of the cooling water increases, and as a result, the pressure loss in the cooling water channel 3 increases. In the conventional example, in order to avoid this, the bypass path 7 and the flow rate adjusting valve 8 are used, but the cost increases due to an increase in the number of parts.
[0008]
In addition, there is a method of increasing the capacity of the cooling water pump 4, but this also increases the power consumption of the auxiliary machine that operates the system as the cost increases, and causes a decrease in the overall efficiency of the system.
[0009]
In addition, most ion exchange resins (particularly anion exchange resins) have a relatively low service temperature, but the temperature of cooling water for cooling the polymer electrolyte fuel cell 1 is about 70 to 80 ° C. . Therefore, the ion exchange resin inside the ion removal filter 6 provided in the cooling water channel 3 is subject to thermal deterioration due to long-term operation under severe conditions in terms of the service temperature, and the life is likely to be shortened. Even when the temperature is good, cooling water of about 70 to 80 ° C. flows in the same manner. This is inefficient and further shortens the life of the ion exchange resin inside the ion removal filter 6.
[0010]
In consideration of the problems of the conventional polymer electrolyte fuel cell system described above, the present invention achieves a high efficiency by extending the life of the ion exchange resin used for maintaining the water quality of the cooling water with a simple structure at a low cost. An object of the present invention is to provide a solid polymer electrolyte fuel cell system and an operation method thereof.
[0011]
[Means for Solving the Problems]
In order to solve the problems as described above, the present invention provides a polymer electrolyte fuel cell that generates power using fuel gas and oxidant gas, a cooling water tank that stores cooling water for cooling the fuel cell, Fuel side condensing means for cooling exhaust fuel gas discharged from the fuel cell and condensing water vapor contained in the exhaust fuel gas and / or exhaust oxidant gas discharged from the fuel cell to cool the exhaust oxidant gas An oxidant side condensing means for condensing water vapor contained in the fuel, and a condensate water tank opened to the atmosphere for storing condensed water condensed by the fuel side condensing means and / or the oxidant side condensing means. the water discharge passage for discharging excess cooling water in the cooling water tank to the condensed water tank from the water tank is provided, the cooling water tank opened to the atmosphere through the water discharge path, and the condensed water tank A solid polymer electrolyte fuel cell system, characterized in that there.
[0012]
The present invention further includes a water supply path having water supply means for supplying water from the condensed water tank to the cooling water tank, and adjusts the quality of the water supplied to the cooling water tank in the water supply path. A solid polymer fuel cell comprising: a water quality treatment means; and operating the water supply means to supply water having its water quality adjusted by the water treatment means to the cooling water tank through the water supply passage. System.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
(Embodiment 1)
FIG. 1 is a configuration diagram showing a polymer electrolyte fuel cell system according to Embodiment 1 of the present invention. A polymer electrolyte fuel cell 11 that generates power using fuel gas and oxidant gas, a cooling water tank 12 that stores cooling water that cools the fuel cell 11, a cooling water channel 13 that circulates the cooling water, and cooling water A cooling water pump 14 as means for circulating the cooling water to the cooling water passage 13, a heat exchanger 15 for cooling the cooling water, and a fuel side condenser for cooling the exhaust fuel gas discharged from the fuel cell 11 and condensing the water vapor contained therein. 16, the air-side condenser 17 that cools the exhaust air discharged from the fuel cell 11 and condenses the water vapor contained therein, and the water that is condensed by the fuel-side condenser 16 and the air-side condenser 17 is opened to the atmosphere. A condensed water tank 18, a water supply path 20 provided with a water supply pump 19 for sending condensed water to the cooling water tank 12, and a water discharge path 21 for discharging excess cooling water inside the cooling water tank 12. .
[0018]
Next, the operation of the polymer electrolyte fuel cell system in the present embodiment will be described.
[0019]
The fuel gas and oxidant gas supplied to the fuel cell 11 are gas whose temperature and humidity are adjusted. Hydrogen gas may be used as the fuel gas, or a hydrogen-rich fuel gas obtained by steam reforming a hydrocarbon gas such as methane. Further, the oxidant gas may be oxygen gas or a gas containing oxygen such as air.
[0020]
Hydrogen in the fuel gas and oxygen in the oxidant gas are consumed by the electrochemical reaction of the fuel cell 11, and water is generated on the oxidant gas side. The oxidant gas discharged from the fuel cell 11 is led to the oxidant-side condenser 17 and the temperature is lowered by exchanging heat with the outside air, and the water vapor contained in the discharged air is condensed and collected as water in the condensation tank 18. The On the other hand, the exhaust fuel gas discharged from the fuel cell 11 is led to the fuel-side condenser 16 to exchange heat with the outside air, so that the temperature is lowered, and the water vapor contained in the exhaust fuel gas is condensed and recovered as water in the condensation tank 18. Is done.
[0021]
Further, in order to keep the temperature of the fuel cell 11 that generates power constant at 70 ° C. or higher, water is circulated by the cooling water pump 14 through the cooling water passage 13, and the heat generated in the fuel cell 11 in the heat exchanger 15 is externally supplied. To release. When the cooling water in the cooling water tank 12 decreases, the water supply pump 19 in the water supply path 20 is operated to supply the water in the condensed water tank 18 to the cooling water tank 12. Even if water enters excessively at this time, the excess cooling water is discharged to the condensing tank 18 through the water discharge passage 21. Further, since the gas above the cooling water tank 12 is connected to the condensed water tank 18 opened to the atmosphere through the water discharge passage 21, the pressure inside the cooling water tank 12 is always equivalent to the state opened to the atmosphere. .
[0022]
If the configuration of the polymer electrolyte fuel cell system in the present embodiment is taken, the pressure inside the cooling water tank 12 is always equivalent to the state opened to the atmosphere. Therefore, when the cooling water temperature changes from the normal temperature before the system operation to the high temperature during power generation, the gas above the cooling water tank 12 expands due to the temperature rise, and the cooling water corresponds to the saturated water vapor pressure at that temperature. Evaporate. That is, the gas above the cooling water tank 12 becomes a wet gas containing saturated water vapor. At this time, the pressure inside the cooling water tank 12 is always equivalent to the state in which the air is opened to the atmosphere. This wet gas enters the condensed water tank 18 while radiating heat to the outside air through the water discharge passage 21. Since the water inside the condensed water tank 18 is usually 40 ° C. or lower, the gas inside the condensed water tank is a gas containing saturated water vapor at 40 ° C. or lower. Therefore, the wet gas from the cooling water tank 12 is cooled to about 40 ° C. by the water discharge path 21 and the condensed water tank 18, and the supersaturated water vapor is condensed and collected as water in the condensed water tank 18.
[0023]
During steady operation, the temperature inside the cooling water tank is a constant temperature of 70 ° C. or higher, so the volume of the gas above the cooling water tank 12 does not change, and the cooling water hardly evaporates. Further, when the system operation is stopped, the gas in the cooling water tank 12 shrinks in volume and the water vapor condenses as the cooling water temperature changes from the high-temperature cooling water during power generation to the normal temperature cooling water after the operation ends. At this time, the gas corresponding to the reduced volume flows into the cooling water tank 12 through the water discharge passage 21 from the condensed water tank 18 opened to the atmosphere, so that the pressure inside the cooling water tank 12 was always opened to the atmosphere even when stopped. It is equivalent to the state.
[0024]
That is, by adopting the configuration of the polymer electrolyte fuel cell system shown in the present embodiment, the pressure inside the cooling water tank 12 can always be maintained in a state equivalent to that in the atmosphere, and the cooling water tank 12 and the cooling water channel can be maintained. It is not necessary to make 13 a structure that can withstand pressure fluctuation.
[0025]
In this embodiment, both the fuel side condenser 16 and the oxidant side condenser 17 are provided. However, even if either the fuel side condenser 16 or the oxidant side condenser 17 is provided, it is equivalent. effective.
[0026]
Further, in the present embodiment, the fuel side condenser 16 and the oxidant side condenser 17 have been described as air-cooled heat exchangers that exchange heat with the outside air, but a water-cooled heat exchanger that exchanges heat with water is used. Has the same effect.
[0027]
(Embodiment 2)
FIG. 2 is a configuration diagram showing a polymer electrolyte fuel cell system according to Embodiment 2 of the present invention. However, the same members and functions as those in FIG.
[0028]
The present embodiment is different from the first embodiment shown in FIG. 1 in that an ion removal filter 22 is provided in the water supply path 20.
[0029]
The ion removal filter 22 removes ions contained in water using an ion exchange resin, and adjusts the quality of water supplied to the cooling water tank 12.
[0030]
When the configuration of the polymer electrolyte fuel cell system shown in the present embodiment is adopted, the water quality supplied to the cooling water tank 12 can be adjusted together with the operation shown in the first embodiment. And since condensed water is about 40 degreeC, it becomes possible to use below the durable temperature of an ion exchange resin, and thermal deterioration can be prevented.
[0031]
Further, when the configuration of the polymer electrolyte fuel cell system shown in the present embodiment is adopted, the following operation can also be realized.
[0032]
When the cooling water inside the cooling water tank 12 is not decreasing, the water supply pump 19 is operated. Then, the water whose water quality has been adjusted is supplied to the cooling water tank 12 through the water supply path 20. Accordingly, the excess cooling water is discharged through the water discharge passage 21 and collected in the condensed water tank 18. The water supplied to the cooling water tank 12 has better water quality than the discharged water. Therefore, the quality of the cooling water can be improved.
[0033]
Moreover, although the cooling water collect | recovered by the condensed water tank 18 is 70 degreeC or more high temperature, since the condensed water condensed and collect | recovered with the fuel side condenser 16 and the air side condenser 17 is about 40 degreeC, it is ion The water passing through the removal filter 22 does not exceed the service temperature of the ion exchange resin. That is, there is no thermal deterioration of the ion exchange resin, and the water quality of the cooling water can be maintained even during system operation while realizing a long life of the ion removal filter 22.
[0034]
This also makes it possible to always maintain the water quality of the cooling water by operating the water supply pump 19 during system operation.
[0035]
Furthermore, in the configuration of the polymer electrolyte fuel cell system shown in the present embodiment, the ion removal filter 22 is in the water supply path 20. Therefore, it is not necessary to use the bypass 7 and the flow rate adjusting valve 8 as shown in the conventional example, and it is not necessary to increase the capacity of the cooling water pump 4. That is, it is possible to realize a low-cost and high-efficiency polymer electrolyte fuel cell system that does not increase the cost due to the increase in the number of parts or increase the capacity or increase the power consumption of auxiliary equipment.
[0036]
Therefore, by adopting the configuration of the polymer electrolyte fuel cell system shown in the present embodiment, it is possible to maintain the water quality of the cooling water and extend the life of the ion removal filter 22 together with the operation described in the first embodiment. At the same time, the overall efficiency of the system can be improved at low cost.
[0037]
Further, an effective operation method of the polymer electrolyte fuel cell system shown in the present embodiment will be described.
[0038]
This operation method is an operation method in which the water supply pump 19 is operated to maintain the quality of the cooling water at one or both of starting and ending the system operation.
[0039]
Cooling water at the time of system startup is low temperature. Thereby, since there is almost no temperature difference between the water supplied to the cooling water tank 12 and the discharged water, there is almost no heat loss. Further, at the end of the system operation, since there is no heat generation in the fuel cell 11, the amount of heat of the cooling water is reduced by the amount of heat between the supplied water and the discharged water, and the cooling water temperature depends on the amount of heat. Go down. That is, there is an effect that the end time can be shortened because the cooling water and the fuel cell 11 are cooled earlier.
[0040]
This operation method is more effective in a polymer electrolyte fuel cell cogeneration system that recovers heat generated from the fuel cell during power generation and uses it for hot water supply or heating.
[0041]
(Embodiment 3)
FIG. 3 is a block diagram showing a polymer electrolyte fuel cell system according to Embodiment 3 of the present invention. However, the same members and functions as those in FIG.
[0042]
In the polymer electrolyte fuel cell system shown in the present embodiment, there is a control unit 23 that controls the operation of the water supply pump 19, and the control unit 23 includes an operation frequency recording means 24 that counts and records the operation frequency of the system. An operation number reset means 25 for resetting the operation number to an initial state is provided.
[0043]
The number-of-operations storage means 24 re-stores a value n + 1 obtained by adding 1 to the number of operations n after the end of system operation. Further, the operation number reset means 25 changes the operation number n of the operation number storage means 24 to 0 in the initial state after the operation of the water supply pump 19 is completed.
[0044]
Next, the operation of the polymer electrolyte fuel cell system in the present embodiment will be described.
[0045]
The operation number n stored in the operation number storage means 24 is compared with the threshold value n1 of the operation number for operating the water supply pump 19, and when n> n1, a command is issued from the controller 23 to The supply pump 19 is activated. A command for ending the operation of the water supply pump 19 is sent from the control unit 23 to the water supply pump 19 and the operation of the water supply pump 19 is terminated. Set to 0. When n <n1 or n = n1, the water supply pump 19 does not operate.
[0046]
The command issued from the control unit 23 to the water supply pump 19 may be any operable time. Further, the command may be issued a plurality of times. When the command is issued a plurality of times, the operation number reset unit 25 sets the operation number n of the operation number storage unit 24 to 0 in the initial state after the operation and the operation end of the water supply pump 19 by the final command.
[0047]
Therefore, the structure of the polymer electrolyte fuel cell system shown in the present embodiment is adopted, and the operation of the water supply pump 19 is managed by the number of operations, whereby the water supply pump 19 that operates to maintain the quality of the cooling water is optimally operated. be able to. As a result, it is possible to maintain the optimum water quality of the cooling water and to prolong the life of the ion removal filter 22. That is, it is a solid polymer fuel cell system that can realize a long life of the ion removal filter 22 that maintains the water quality of the cooling water.
[0048]
In the present embodiment, the operation number storage means 24 stores the value n + 1, which is obtained by adding 1 to the operation number n after the end of the system operation. The same effect can be obtained at any time of system operation including termination.
[0049]
(Embodiment 4)
FIG. 4 is a configuration diagram showing a polymer electrolyte fuel cell system according to Embodiment 4 of the present invention. However, the same members and functions as those in FIG.
[0050]
In the polymer electrolyte fuel cell system shown in the present embodiment, there is a control unit 26 for controlling the operation of the water supply pump 19, and the control unit 26 includes an operation time recording means 27 for counting and recording the operation time of the system. An operation time reset means 28 for resetting the operation time to the initial state is provided.
[0051]
The operation time storage means 27 counts the accumulated time of system operation and stores the time again. The operation time resetting means 28 changes the operation time of the operation time storage means 27 to 0 in the initial state after the operation of the water supply pump 19 is completed.
[0052]
Next, the operation of the polymer electrolyte fuel cell system in the present embodiment will be described.
[0053]
The operation time T stored in the operation time storage means 27 is compared with the operation time threshold value T1 for operating the water supply pump 19, and when T> T1, a command is issued from the control unit 26 to The supply pump 19 is activated. A command for ending the operation of the water supply pump 19 is issued from the control unit 26 to the water supply pump 19 and the operation of the water supply pump 19 is terminated. Set to 0. When T <T1 or T = T1, the water supply pump 19 does not operate.
[0054]
The command issued from the control unit 26 to the water supply pump 19 may be any time during which operation is possible. Further, the command may be issued a plurality of times. When the command is issued a plurality of times, the operation time T of the operation time storage means 27 is set to 0 in the initial state by the operation time reset means 28 after the operation / operation of the water supply pump 19 is completed according to the final instruction.
[0055]
Therefore, by taking the configuration of the polymer electrolyte fuel cell system shown in the present embodiment and managing the operation of the water supply pump 19 by the operation time, the water supply pump 19 that operates to maintain the water quality of the cooling water is optimally operated. be able to. As a result, it is possible to maintain the optimum water quality of the cooling water and to prolong the life of the ion removal filter 22. That is, it is a solid polymer fuel cell system that can realize a long life of the ion removal filter 22 that maintains the water quality of the cooling water.
[0056]
(Embodiment 5)
FIG. 5 is a block diagram showing a polymer electrolyte fuel cell system according to Embodiment 5 of the present invention. However, the same members and functions as those in FIG.
[0057]
The polymer electrolyte fuel cell system shown in the present embodiment includes a water quality detector 29 that detects the quality of cooling water circulating in the cooling water channel 13 and a control unit 30 that controls the operation of the water supply pump 19. .
[0058]
Further, the control unit 30 includes a first level value and a second level value. The first level value is a threshold value for operating the water supply pump 19 when the value indicated by the water quality detector 29 is deteriorated from the value. The second level value is a threshold value for stopping the operation of the water supply pump 19 when the value indicated by the water quality detector 29 becomes better than that value during the operation of the water supply pump 19.
[0059]
In this embodiment, a conductivity meter is used as the water quality detector 29 in particular. Further, the conductivity a1 is used as the first level value, and the conductivity a2 is used as the second level value.
[0060]
Next, the operation of the polymer electrolyte fuel cell system in the present embodiment will be described.
[0061]
The electrical conductivity a measured by the water quality detector 29 is compared with the electrical conductivity a1 which is the first level value for operating the water supply pump 19, and when a> a1, an instruction is issued from the control unit 30. The water supply pump 19 is activated. The water supply pump 19 continues to operate until a <a2.
[0062]
During the operation of the water supply pump 19, the conductivity a measured by the water quality detector 29 is compared with the conductivity a2 which is the second level value for stopping the operation of the water supply pump 19, and a < At a2, a command is issued from the control unit 30, and the operation of the water supply pump 19 is stopped. The water supply pump 19 continues to stop until a> a1 again.
[0063]
Note that the command issued from the control unit 30 to the water supply pump 19 may be any operable time.
[0064]
Therefore, the structure of the polymer electrolyte fuel cell system shown in the present embodiment is adopted, and the operation of the water supply pump 19 is managed by the quality of the cooling water, so that the water supply pump 19 that operates to maintain the quality of the cooling water is optimal. Can be operated. As a result, it is possible to maintain the optimum water quality of the cooling water and to prolong the life of the ion removal filter 22. That is, it is a solid polymer fuel cell system that can realize a long life of the ion removal filter 22 that maintains the water quality of the cooling water.
[0065]
In this embodiment, conductivity measurement using a conductivity meter has been described as a cooling water quality detection method in particular, but the same effect can be obtained even if the water quality of the cooling water is controlled using pH. .
[0066]
【The invention's effect】
As is apparent from the above description, the present invention can be realized by providing a polymer electrolyte fuel cell system capable of always maintaining the pressure of the cooling water channel in a state equivalent to that in the atmosphere.
[0067]
Also, to maintain the water quality of the cooling water, to prevent the thermal deterioration of the ion removal filter and to extend the life, and to provide a solid polymer fuel cell system with low overall cost and high system efficiency. Can be realized.
[0068]
In addition, it is possible to provide a polymer electrolyte fuel cell system with less heat loss and shorter end time by operating the water supply means at the start or end of system operation. it can.
[0069]
Furthermore, by controlling the operation of the water supply means based on the number of operations or operation time or the quality of the cooling water, it is possible to maintain the optimum cooling water quality and extend the life of the ion removal filter. Providing a system can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a polymer electrolyte fuel cell system according to Embodiment 1 of the present invention. FIG. 2 is a block diagram showing a polymer electrolyte fuel cell system according to Embodiment 2 of the present invention. FIG. 4 is a block diagram showing a polymer electrolyte fuel cell system according to Embodiment 3 of the present invention. FIG. 4 is a block diagram showing a polymer electrolyte fuel cell system according to Embodiment 4 of the present invention. FIG. 6 is a block diagram showing a conventional polymer electrolyte fuel cell system in Embodiment 5. FIG. 6 is a block diagram showing a conventional polymer electrolyte fuel cell system.
DESCRIPTION OF SYMBOLS 11 Fuel cell 12 Cooling water tank 13 Cooling water path 14 Cooling water pump 15 Heat exchanger 22 Ion removal filter 16 Fuel side condenser 17 Air side condenser 18 Condensed water tank 19 Water supply pump 20 Water supply path 21 Water discharge path 23, 26, 30 Control unit 24 Operation number storage means 25 Operation number reset means 27 Operation time storage means 28 Operation time reset means 29 Water quality detector

Claims (2)

A fuel cell of the polymer electrolyte for generating electric power using a fuel gas and an oxidant gas, and cooling water tank to store the cooling water for cooling the fuel cell, the exhaust fuel gas is cooled to be discharged from the fuel cell an oxidant side condensing means for condensing the water vapor contained exhaust oxidant gas discharged from the fuel side condensing means and / or said fuel cell to condense the water vapor in the cooled exhaust oxidant gas contained in the exhaust fuel gas, A condensate water tank opened to the atmosphere for storing condensed water condensed by the fuel side condensing means and / or the oxidant side condensing means, and an excess of the cooling water tank from the cooling water tank to the condensed water tank the water discharge passage for discharging the cooling water is provided, the cooling water tank polymer electrolyte fuel cell characterized by being open to the atmosphere through the water discharge path, and the condensed water tank Stem. A water supply path having water supply means for supplying water from the condensed water tank to the cooling water tank, and provided with water quality processing means for adjusting the quality of water supplied to the cooling water tank in the water supply path; polymer electrolyte fuel cell system according to claim 1, wherein the supplying water conditioning water in the water treatment means to the cooling water tank through the water supply passage by operating the water supply means .

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