JP3589175B2 - Fuel cell device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel cell device that supplies fuel and air to a fuel cell, converts chemical energy into electric energy, and generates power.
[0002]
[Prior art]
2. Description of the Related Art In recent years, fuel cell technology that enables clean exhaust and high energy efficiency has attracted attention with respect to environmental problems, in particular, the problem of air pollution caused by vehicle exhaust gas and global warming caused by carbon dioxide. 2. Description of the Related Art A fuel cell is an energy conversion system that supplies hydrogen or a hydrogen-rich reformed gas and air serving as a fuel to a polymer membrane-electrocatalyst composite to cause an electrochemical reaction to convert chemical energy into electric energy. . Among them, a solid polymer electrolyte fuel cell having a particularly high output density has attracted attention as a power source for a mobile body such as an automobile.
[0003]
In a polymer electrolyte membrane fuel cell using a polymer electrolyte membrane as an electrolyte, an electrolyte membrane is composed of an anode electrode (hydrogen electrode) supplied with hydrogen as a fuel and a cathode electrode (air electrode) supplied with air. It is the structure arranged between. When hydrogen is supplied to the hydrogen electrode, it is dissociated into hydrogen ions and electrons, the hydrogen ions pass through the electrolyte membrane, and the electrons generate electric power through an external circuit and move to the air electrode.
[0004]
On the other hand, at the air electrode, oxygen in the supplied air reacts with the hydrogen ions and the electrons to generate water, which is discharged to the outside.
[0005]
The electrolyte membrane as described above functions as an ion conductive electrolyte by being saturated with water, and also has a function of separating hydrogen and oxygen. Conversely, if the water content is insufficient, the ionic resistance will increase, and hydrogen and oxygen will be mixed, making it impossible to generate power as a fuel cell.
[0006]
On the other hand, when the hydrogen ions separated at the hydrogen electrode by the power generation pass through the electrolyte membrane, the water also moves together, so that the hydrogen electrode side tends to dry. Also, when the amount of water vapor contained in the supplied hydrogen or air is small, the electrolyte membrane tends to dry near the respective reaction gas inlets.
[0007]
For this reason, the electrolyte membrane in the polymer electrolyte fuel cell needs to be humidified by supplying water from the outside. As a method of humidifying the electrolyte membrane, a method of collecting and using water generated at an air electrode is described in, for example, JP-A-7-272740 and JP-A-11-185782. This means that the water (moisture contained in the air) generated at the cathode of the fuel cell is cooled and condensed by a condenser, collected and stored in a water storage tank, and water is pumped directly from the water storage tank by a pump. It is used to humidify the gas (hydrogen and air) supplied to the fuel cell and to cool the fuel cell.
[0008]
Such a configuration is also described in SAE paper 2000-01-1061 and SAE paper 98C054.
[0009]
[Problems to be solved by the invention]
By the way, when supplying the water recovered from the air electrode to the humidifier, if the supply amount of water is small, the temperature of the water decreases greatly due to the heat taken from the water by evaporation in the humidifier, and as a result, the fuel The dew point of the gas supplied to the battery decreases, and the output of the fuel cell decreases. Therefore, it is necessary to increase the supply amount of the humidifying water to the humidifier. Further, although the fuel cell has high thermal efficiency, since the heat loss from exhaust gas is small as in the case of an internal combustion engine, it is necessary to increase the supply amount of cooling water even in consideration of cooling the fuel cell.
[0010]
However, if the amount of water pumped from the water storage tank by the pump is large, a vortex is generated near the humidification water outlet of the water storage tank to cause cavitation, and the cavitation concentrates stress only near the humidification water outlet of the water storage tank. Instead, the efficiency of the pump is reduced and the performance of the pump itself is deteriorated.
[0011]
Therefore, an object of the present invention is to prevent the occurrence of cavitation when pumping water from a water storage tank using humidifying water.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 provides a water storage tank for collecting and storing water generated at an air electrode of a fuel cell, and at least a fuel and air supplied to the fuel cell. A humidifier for humidifying one of the humidifiers is provided, the water storage tank and the humidifier are connected by a humidification water supply passage having a humidification water supply pump, and a humidification water return passage having one end connected to the humidifier. The other end is connected to a humidification water supply passage between the water storage tank and the humidification water supply pump, and a condenser for condensing steam discharged from the air electrode between the air electrode of the fuel cell and the water storage tank. The capacitor is disposed above the outlet of the cathode in the fuel cell, while the second water storage tank is disposed below the outlet of the cathode, and the second water storage tank is connected to the cathode. Capacitor It is constituted connected near the cathode outlet between.
[0015]
The invention of claim 2 is the configuration of the invention of claim 1, there is a water watertable second water storage tank configured so as to use as humidification water.
[0016]
The invention of claim 3, in the configuration of the invention of claim 2, there is a structure in which a pump for pumping the water in the second water storage tank to storage tank.
[0017]
A fourth aspect of the present invention, in the configuration of the invention of claim 2, and a second water storage tank, a humidification water supply pump passage that connects the humidifying water supply passage between the water storage tank is provided, opening and closing the passage The opening and closing valve is provided.
[0018]
According to a fifth aspect of the present invention, in the configuration according to any one of the first to fourth aspects, a cooling water supply passage through which cooling water for cooling the fuel cell passes is connected to a humidifier side end of the humidification water supply passage. In addition, a cooling water return passage for cooling water discharged from the fuel cell after cooling is connected to a humidifier side end of the humidification water return passage.
[0019]
【The invention's effect】
According to the first aspect of the present invention, excess water pumped out of the water storage tank by the humidification water supply pump and not used (consumed) for humidification by the humidifier passes through the humidification water return passage and the humidification water supply pump. The water is returned to the tank and this returned water is supplied to the humidifier by the humidification water supply pump together with the water in the water storage tank, so the amount of water to be pumped out of the water storage tank is only the amount used for humidification. The generation of eddy currents near the humidification water outlet of the water storage tank is avoided to prevent cavitation, stress concentration near the humidification water outlet of the water storage tank, reduction in pump efficiency, and deterioration of the performance of the pump itself. Can be prevented.
Further, since the second water storage tank located below the air electrode outlet is provided near the air electrode outlet of the fuel cell, water condensed on the way to the condenser disposed above the air electrode outlet, The water directly discharged from the pole outlet is taken into the second water storage tank, and the backflow of water to the air electrode is avoided, so that the performance of the fuel cell can be prevented from deteriorating.
[0022]
According to the invention of claim 2 can be water taken into the second water storage tank is also effectively used as humidifying water.
[0023]
According to the invention of claim 3 , the water taken in the second water storage tank can be reliably supplied to the water storage tank by the pump.
[0024]
According to the invention of claim 4, the water in the second water storage tank can be pumped out by the humidification water supply pump by opening the on-off valve while the humidification water supply pump is operated. The amount of water drawn from the tank can be further reduced, and the generation of a vortex near the humidification water outlet of the water storage tank can be more reliably prevented.
[0025]
According to the fifth aspect of the present invention, even if excess water pumped out of the water storage tank by the humidification water supply pump and not used for humidification by the humidifier is used for cooling the fuel cell, Is returned between the humidification water supply pump and the water storage tank through the cooling water return passage and the humidification water return passage, and the returned water can be supplied to the humidifier by the humidification water supply pump together with the water in the water storage tank. The amount of water pumped out of the tank is reduced by the amount used for humidification, which prevents eddy currents near the humidification water outlet of the storage tank and prevents cavitation. , Stress deterioration of the pump, and deterioration of the performance of the pump itself can be prevented.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0027]
FIG. 1 is an overall configuration diagram of a fuel cell device according to a first embodiment of the present invention. A high-pressure hydrogen tank 1 in which hydrogen as fuel is stored and a fuel inlet 3ai of a hydrogen electrode 3a of the fuel cell 3 are connected by a fuel supply passage 5. A pressure reducing valve 7, a pressure control valve 9, a circulator 11, and a humidifier 13 are sequentially provided in the fuel supply passage 5 from the hydrogen tank 1 side.
[0028]
The pressure reducing valve 7 reduces the pressure of the hydrogen supplied from the hydrogen tank 1 to a predetermined pressure. The pressure control valve 9 controls the pressure of hydrogen reduced by the pressure reducing valve 7 to a desired pressure corresponding to the operating conditions of the fuel cell device under the control of a control unit (not shown) such as a microcomputer. The circulator 11 is connected to the other end of the fuel recirculation passage 15, one end of which is connected to the fuel outlet 3 ao of the hydrogen electrode 3 a in the fuel cell 3, and removes excess hydrogen that cannot contribute to power generation in the fuel cell 3. Then, the fuel is returned to the fuel supply passage 5 through the fuel recirculation passage 15. The humidifier 13 humidifies hydrogen supplied to the fuel cell 3 and air described later to a desired humidity (approximately 100% relative humidity).
[0029]
On the other hand, the air inlet 3bi of the air electrode 3b of the fuel cell 3 and the compressor 17 are connected by an air supply passage 19. The filter 21 and the humidifier 13 are sequentially provided in the air supply passage 19 from the compressor 17 side. The filter 21 removes dust in the cooled air.
[0030]
A capacitor 25 is connected to the other end of the air discharge passage 23, one end of which is connected to an air outlet 3bo serving as an outlet of the air electrode 3b in the fuel cell 3. The cooling water inlet passage 29 and the cooling water outlet passage 31 are respectively connected to the condenser 25, and the cooling water is supplied to the condenser 25 from a cooling system (not shown). In the condenser 25, the steam component in the water (steam component and liquid component) generated by the reaction at the air electrode 3b and the excess steam component due to the air consumption at the air electrode 3b are cooled / cooled by the cooling water. The condensed liquid is liquefied and introduced into the separator 33.
[0031]
The vertical position of the condenser 25 is higher than the air outlet 3bo of the air electrode 3b of the fuel cell 3 because it is necessary to install the separator 33 below the condenser 25 and the water storage tank 39 below the separator 33.
[0032]
In the separator 33, the condensed water is separated from the air, and the air is adjusted to a desired pressure according to the operating conditions by a pressure regulating valve 37 provided in the air discharge passage 35 and controlled by the control unit (not shown). At the same time, the pressure difference between the hydrogen electrode 3a and the air electrode 3b in the fuel cell 3 is adjusted to be within a predetermined range. On the other hand, the water separated from the air by the separator 33 is collected in the water storage tank 39.
[0033]
The water storage tank 39 and the humidifier 13 are connected by a humidification water supply passage 43 provided with a humidification water supply pump 41, and the other end of the humidification water return passage 45 connected to the humidifier 13 at one end is connected to the water storage tank 39. The humidification water supply pump 43 is connected to a humidification water supply passage 43a. Further, the humidifier 13 and the fuel cell 3 are connected by a cooling water supply passage 47 and a cooling water return passage 49, respectively. That is, the water in the water storage tank 39 is pumped out by the humidification water supply pump 41 and humidifies the hydrogen and the air by reaching the humidifier 13, and further reaches the fuel cell 3 through the cooling water supply passage 47 and reaches the fuel cell 3. After cooling the cooling water 3, the cooling water is returned to the humidification water supply passage 43 a via the cooling water return passage 49, the humidifier 13, and the humidification water return passage 45.
[0034]
According to the above-described configuration, the humidifier 13 is pumped up from the water storage tank 39 by the humidification water supply pump 41 and reaches the humidifier 13. Through the humidification water supply pump 43, the water is returned to the humidification water supply passage 43a on the downstream side of the water storage tank 39, and the returned water and the water in the water storage tank 39 corresponding to the amount consumed by the humidifier 13. It is supplied to the humidifier 13.
[0035]
For this reason, the amount of water pumped up from the water storage tank 39 by the humidification water supply pump 41 is reduced by the amount consumed by the humidifier 13, and as a result, vortex generation near the humidification water outlet of the water storage tank 39 occurs. This avoids the occurrence of cavitation, thereby preventing stress concentration in the vicinity of the humidification water outlet of the water storage tank 39, reduction in efficiency of the humidification water supply pump 41, and deterioration of the performance of the humidification water supply pump 41 itself.
[0036]
Further, by adjusting the pressure of the air separated from the water by the separator 33 by the pressure adjusting valve 37, a predetermined air pressure can be given to the water storage tank 39, so that the head of the humidification water supply pump 41 can be reduced. In addition, the pressure difference between the hydrogen electrode 3a and the air electrode 3b in the fuel cell 3 can be suppressed to a predetermined range, which can contribute to improving the performance of the fuel cell 3.
[0037]
FIG. 2 is an overall configuration diagram of a fuel cell device according to a second embodiment of the present invention, in which a cooling system for the fuel cell 3 is different from a humidifying water supply system for the humidifier 13 in a cooling water introduction passage. This is an example in which a fuel cell 51 and a cooling water discharge passage 53 are connected to the fuel cell 3 respectively. Other configurations are the same as those in FIG. Therefore, in this case, the water pumped by the humidification water supply pump 41 reaches the humidifier 13 via the humidification water supply passage 43, and then passes through the humidification water return passage 45 to the water storage tank 39 and the humidification water supply pump 41. Is returned to the humidification water supply passage 43a.
[0038]
In the example of FIG. 2 as well, the water flowing out of the humidifier 13 is returned to the humidification water supply passage 43a between the water storage tank 39 and the humidification water supply pump 41. The amount of water to be pumped is reduced by the amount consumed by the humidifier 13, and vortex generation near the humidification water outlet of the water storage tank 39 is avoided, cavitation is prevented, and humidification water in the water storage tank 39 is prevented. It is possible to prevent stress concentration near the outlet, decrease in efficiency of the humidification water supply pump 41, and deterioration of performance of the humidification water supply pump 41 itself.
[0039]
FIG. 3 is an overall configuration diagram of a fuel cell device according to a third embodiment of the present invention. In FIG. 3, an air discharge passage 23 connected to an air outlet 3bo of an air electrode 3b in the fuel cell 3 is different from the example of FIG. A second water storage tank 55 is connected via a recovery passage 57 near the air outlet 3bo. The second water storage tank 55 is located below the air outlet 3bo of the air electrode 3b in the fuel cell 3, and is provided with a liquid level sensor 59 for detecting the liquid level of the collected water.
[0040]
The second water storage tank 55 and the water storage tank 39 are connected by a discharge passage 61. The discharge passage 61 is provided with a pump 63 for supplying water in the second water storage tank 55 to the water storage tank 39 by pressure. Other configurations are the same as those in FIG.
[0041]
FIG. 4 is an explanatory diagram showing a vertical positional relationship among the air outlet 3bo of the air electrode 3b, the condenser 25, and the second water storage tank 55 in the example of FIG. That is, the condenser 25 is disposed above the air outlet 3bo, and the second water storage tank 55 is disposed below the air outlet 3bo.
[0042]
In the example of FIG. 3 described above, as shown in FIG. 4, the steam S flowing out of the air outlet 3bo of the air electrode 3b toward the condenser 25 disposed above the air electrode 3b flows in the air discharge passage 23 in the middle. The condensed water L1 and the water L2 discharged from the air outlet 3bo are collected in the second water storage tank 55 disposed below the air outlet 3bo. Therefore, it is possible to avoid a phenomenon that water flows backward toward the air outlet 3bo toward the air discharge passage 23, prevent water from accumulating in the fuel electrode 3a and the air electrode 3b, and prevent performance deterioration as a fuel cell. it can.
[0043]
The water collected in the second water storage tank 55 is pumped to the water storage tank 39 by driving the pump 63 so that the liquid level is maintained in a predetermined range by the liquid level sensor 59, and is used as humidifying water.
[0044]
FIG. 5 is an overall configuration diagram of a fuel cell device according to a fourth embodiment of the present invention. An on-off valve 65 is provided instead of the pump 63 in FIG. 3, and the discharge passage 61 is connected to the water storage tank 39 and the humidifying water. It is connected to a humidification water supply passage 43a between the supply pump 41 and the humidification water supply passage 43a. Other configurations are the same as those in FIG.
[0045]
When the humidification water supply pump 41 is operated, the upstream side thereof has a negative pressure. Therefore, when the on-off valve 65 is opened in this state, the water in the second water storage tank 55 is released from the water storage tank 39 by the suction force due to the negative pressure. It is supplied downstream. The on / off control of the on-off valve 55 is performed by the control unit (not shown) so that the amount of water in the second water storage tank 55 is detected by the liquid level sensor 59 and falls within a predetermined range.
[0046]
In this case, by using an on-off valve 65 instead of the pump 63 in FIG. 3, the cost can be reduced by that much, and the amount of water pumped from the water storage tank 39 by the humidification water supply pump 41. However, the amount of water consumed by the humidifier 13 is subtracted from the amount supplied from the second water storage tank 55, and the amount is further reduced, so that the generation of a vortex near the humidification water outlet of the water storage tank 39 is more reliably avoided. This can reliably prevent stress concentration near the humidification water outlet of the water storage tank 39, decrease in efficiency of the humidification water supply pump 41, and deterioration of performance of the humidification water supply pump 41 itself.
[0047]
In the examples of FIGS. 3 and 5, the cooling system for the fuel cell 3 is provided separately from the humidifying water supply system. However, as in the example of FIG. A configuration in which system piping is connected may be employed.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a fuel cell device according to a first embodiment of the present invention.
FIG. 2 is an overall configuration diagram of a fuel cell device according to a second embodiment of the present invention.
FIG. 3 is an overall configuration diagram of a fuel cell device according to a third embodiment of the present invention.
FIG. 4 is an explanatory diagram showing a vertical positional relationship among an air outlet of a cathode of a fuel cell, a condenser, and a second water storage tank in the embodiment of FIG. 3;
FIG. 5 is an overall configuration diagram of a fuel cell device according to a fourth embodiment of the present invention.
[Explanation of symbols]
3 fuel cell 3b air electrode 3bo air outlet 13 humidifier 25 condenser 33 separator 37 pressure regulating valve 39 storage tank 41 humidification water supply pump 43, 43a humidification water supply passage 45 humidification water return passage 47 cooling water supply passage 49 cooling water return passage 55 second water storage tank 61 discharge passage 63 pump 65 on-off valve

Claims (5)

A water storage tank for collecting and storing water generated at the air electrode of the fuel cell is provided, and a humidifier for humidifying at least one of fuel and air supplied to the fuel cell is provided. The humidifier is connected to a humidification water supply passage provided with a humidification water supply pump, and the other end of the humidification water return passage, one end of which is connected to the humidifier, is connected between the water storage tank and the humidification water supply pump. Connected to the humidification water supply passage, and provided between the air electrode of the fuel cell and the water storage tank, a condenser for condensing the vapor discharged from the air electrode. The second water storage tank is disposed below the outlet of the air electrode while being disposed above, and the second water storage tank is connected near the air electrode outlet between the air electrode and the condenser. Features and That the fuel cell device. 2. The fuel cell device according to claim 1, wherein the water stored in the second water storage tank is used as humidification water. 3. The fuel cell device according to claim 2, further comprising a pump for pumping water in the second water storage tank to the water storage tank. 3. The humidification water supply passage between the second water storage tank and the humidification water supply pump and the water storage tank is provided with a passage for connecting the humidification water supply passage, and an on-off valve for opening and closing this passage is provided. Fuel cell device. The cooling water supply passage through which the cooling water for cooling the fuel cell passes is connected to the humidifier side end of the humidification water supply passage, and the cooling water return passage for the cooling water discharged from the fuel cell after cooling is connected to the humidification water supply passage. The fuel cell device according to any one of claims 1 to 4, wherein the fuel cell device is connected to a humidifier-side end of the return passage.

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