JP2004172049A - Operation method of power generation system and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To continue power generation by avoiding freezing of product water even when a fuel cell is made started below freezing point. <P>SOLUTION: The power generation system is provided with a fuel cell 1 equipped with an anode and a cathode on either side of a solid polymer electrolyte film and generating power as the anode is supplied with hydrogen and the cathode is supplied with air. When the fuel cell 1 is started or stopped below 0°C, product water produced in accordance with power generation is made antifreeze, by supplying alcohol to an evaporator 3 fitted halfway through an air supply channel 21 and supplying alcohol vapor together with air to the cathode of the fuel cell 1. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a power generation system including a solid polymer electrolyte membrane fuel cell and a method of operating the fuel cell.
[0002]
[Prior art]
A fuel cell mounted on a fuel cell vehicle or the like includes an anode and a cathode on both sides of a solid polymer electrolyte membrane, supplies fuel (eg, hydrogen gas) to the anode, and oxidizer (eg, oxygen or air) to the cathode. And the chemical energy involved in the oxidation-reduction reaction of these reaction gases is directly extracted as electric energy.
In this fuel cell, hydrogen is ionized at the anode and travels through the solid polymer electrolyte, and electrons travel to the cathode through an external load, and react with oxygen to produce water through a series of electrochemical reactions. Energy can be extracted, and power generation involves generation of water.
[0003]
Therefore, if the fuel cell is stopped with the generated water remaining in the fuel cell and the outside temperature is low for a long time, such as below freezing, the remaining generated water freezes and reacts with the reaction gas (fuel and oxidation). Block the flow path and diffusion layer of the agent) and deteriorate the starting performance. In order to cope with this, there is a technique in which generated water in the fuel cell is discharged and then the fuel cell is stopped.
However, even if the generated water is discharged before the fuel cell is stopped, when the fuel cell starts generating power below the freezing point, the generated water newly generated by the power generation freezes and the reaction gas flow path and diffusion layer In some cases, and it becomes difficult to continue power generation.
[0004]
Therefore, conventionally, at the time of starting below the freezing point, after the temperature around the power generation unit of the fuel cell is increased to 0 ° C. or higher, the power generation of the fuel cell is started, and the power generation can be continued.
Here, as a method of heating the fuel cell, a method using an electric heater or a method of supplying heated coolant to the fuel cell is generally adopted. Further, as another heating method, there is a method of causing an exothermic reaction between hydrogen and oxygen on a cathode catalyst or an anode catalyst (for example, see Patent Document 1).
[0005]
As a technique for lowering the freezing point, a technique for preventing freezing of humidified water by mixing a freezing point depressant with humidifying water for humidifying a reaction gas (fuel gas or oxidizing gas) supplied to a fuel cell (for example, And a cooling liquid for cooling a fuel cell, which is mixed with a freezing point depressant to prevent the cooling liquid from freezing (for example, see Patent Document 3). However, these technologies are not technologies for preventing freezing of generated water generated by the fuel cell, and even if these technologies can be used to prevent the humidifying water and the cooling liquid from freezing, they are not freezing. Does not mean that the fuel cell can continue to generate power.
[0006]
[Patent Document 1]
JP 2001-189164 A
[Patent Document 2]
JP 2000-208156 A
[Patent Document 3]
U.S. Pat. No. 6,316,135
[0007]
[Problems to be solved by the invention]
However, if the fuel cell is heated until the temperature around the power generation section of the fuel cell becomes 0 ° C. or higher at the time of starting below the freezing point as in the conventional case, the heat capacity of the fuel cell is large, so a large amount of heat is required, and the heating means is electrically powered. Regardless of whether a heater, a heated cooling liquid, or an exothermic reaction on a catalyst is employed, a long time is required for heating. In particular, when a fuel cell is used as an energy source of a moving body, such as a fuel cell vehicle, there is a problem in that if a long time is required for starting, convenience is lost.
In view of the above, the present invention provides a power generation system and a fuel cell operating method that enable continuation of power generation below freezing point by converting water generated by power generation into antifreeze liquid.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 is a fuel that has an anode and a cathode on both sides of a solid polymer electrolyte membrane, a fuel is supplied to the anode, and an oxidant is supplied to the cathode to generate power. A power generation system including a battery (for example, a fuel cell 1 in an embodiment described later), wherein a chemical substance that lowers the freezing point of water when the fuel cell is started and / or stopped at a temperature of 0 degrees Celsius or less. Is supplied to the cathode.
With this configuration, a chemical substance that lowers the freezing point of water is included in generated water generated by power generation at the time of starting and / or stopping at a temperature of 0 degrees Celsius or less. As a result, the generated water can be prevented from freezing.
[0009]
According to a second aspect of the present invention, there is provided a fuel cell having an anode and a cathode on both sides of a solid polymer electrolyte membrane, wherein fuel is supplied to the anode, and an oxidant is supplied to the cathode to generate power (for example, an embodiment described below). A fuel cell system according to any one of the preceding claims, comprising a fuel cell 1) for supplying an oxidant to the cathode (for example, an air supply channel 21 in an embodiment described later) and a freezing point of water. A freezing point depressant supply unit (for example, an evaporator 3, an injector 6, and an alcohol supply passage 24 in an embodiment described later) for supplying a chemical substance to be supplied to the oxidant supply passage. System.
With this configuration, when the generated water generated by the power generation is likely to freeze, a chemical substance that lowers the freezing point of the water can be supplied to the cathode of the fuel cell. Chemicals that lower the freezing point of the water can be included, lowering the freezing point of the generated water and preventing freezing of the generated water.
[0010]
According to a third aspect of the present invention, in the second aspect, the freezing point depressant supply means includes an evaporator (e.g., an evaporator 3 in an embodiment described later) for evaporating the chemical substance. The chemical substance evaporated by the evaporator is supplied to an oxidant supply flow path.
With this configuration, it is possible to heat the vicinity of the power generation site by the sensible heat of the vapor of the chemical substance and the condensation heat when the vapor condenses.
[0011]
According to a fourth aspect of the present invention, in the second aspect of the invention, there is provided a removing means for removing the chemical substance remaining in the cathode offgas discharged from the cathode (for example, a catalytic combustor 4 in an embodiment described later). ).
With such a configuration, it becomes possible to remove the freezing point depressing chemical substance remaining in the cathode off-gas.
[0012]
The invention according to claim 5 is the invention according to claim 4, wherein the removing means is a combustion means for burning the chemical substance (for example, a catalytic combustor 4 in an embodiment described later). I do.
With such a configuration, it becomes possible to burn and remove the freezing point depressing chemical substance remaining in the cathode offgas.
[0013]
According to a sixth aspect of the present invention, in the third aspect of the invention, there is provided a combustion means capable of burning the chemical substance remaining in the cathode offgas discharged from the cathode (for example, a catalytic combustor in an embodiment described later). 4), wherein the heat generated by the combustion means is used as a heat source of the evaporator.
With this configuration, the freezing point depressing chemical substance remaining in the cathode offgas can be removed by burning by the combustion means, and the freezing point depressing chemical substance is generated by the heat generated by the combustion means in the evaporator. Can be evaporated, so that the chemical substance can be effectively used.
[0014]
The invention according to claim 7 is the invention according to any one of claims 2 to 6, wherein at least a portion of the cathode offgas discharged from the cathode is returned to the oxidant supply flow passage. (For example, a cathode off-gas circulation channel 25 in an embodiment described later).
With such a configuration, mixing of the freezing point depressing chemical substance and the produced water can be promoted, and the freezing point depressing chemical substance remaining in the cathode offgas can be circulated and reused.
[0015]
The invention according to claim 8 is the invention according to any one of claims 1 to 7, wherein the supply amount of the chemical substance supplied to the cathode is set according to the temperature.
With this configuration, it is possible to reliably supply the cathode with a chemical substance in an amount necessary for preventing the generated water from freezing.
[0016]
The invention according to claim 9 is the invention according to any one of claims 1 to 8, wherein the chemical substance is at least one of alcohols such as methanol, ethanol, propanol, ethylene glycol, and glycerin. It is characterized by that.
With this configuration, freezing of the generated water can be prevented without adversely affecting the solid polymer electrolyte membrane. Further, a part of the chemical substance composed of alcohols supplied to the cathode causes an oxidation reaction on the cathode catalyst to generate heat, thereby heating the vicinity of the power generation site.
The chemical substance supplied to the cathode may be composed of only one of these alcohols, or may be composed of a mixture of two or more.
[0017]
According to a tenth aspect of the present invention, there is provided a fuel cell having an anode and a cathode on both sides of a solid polymer electrolyte membrane, wherein fuel is supplied to the anode, and an oxidant is supplied to the cathode to generate power (for example, an embodiment described below). In the method of operating the fuel cell 1) according to the aspect, when the generated water generated by the power generation of the fuel cell is likely to be frozen, a chemical substance that lowers the freezing point of water is supplied to the cathode to thereby perform the generation. It is characterized in that the chemical substance is dissolved in water, and the produced water is made into an antifreeze.
With this configuration, it is possible to prevent the generated water from freezing even when the generated water is likely to freeze.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a power generation system and a method of operating a fuel cell according to the present invention will be described with reference to FIGS. 1 to 8.
[First Embodiment]
First, a first embodiment of a power generation system and a method of operating a fuel cell according to the present invention will be described with reference to the drawings of FIGS.
FIG. 1 is a schematic configuration diagram of the power generation system according to the first embodiment.
The fuel cell 1 is a unit fuel cell (unit cell) formed by sandwiching a solid polymer electrolyte membrane made of, for example, a solid polymer ion exchange membrane between an anode and a cathode from both sides and sandwiching a pair of separators from both sides. A stack composed of a plurality of layers is stacked. When hydrogen gas is supplied as fuel to the anode and air containing oxygen is supplied to the cathode, hydrogen ions generated by a catalytic reaction at the anode are converted into a solid polymer electrolyte membrane. , And travels to the cathode, where an electrochemical reaction occurs with oxygen at the cathode to generate power and generate water.
[0019]
Hydrogen gas supplied from a fuel supply device (not shown) is supplied to an anode of the fuel cell 1 through an ejector 11 and a hydrogen supply flow path 12. A portion of the hydrogen gas supplied to the fuel cell 1 is used for power generation, and unreacted hydrogen gas not used for power generation is discharged from the fuel cell 1 as an anode off-gas, and is passed through an anode off-gas circulation channel 13 to an ejector. The fuel is sucked into the fuel cell 11, mixed with fresh hydrogen gas supplied from the fuel supply device, and supplied to the anode of the fuel cell 1 again.
[0020]
The air is pressurized to a predetermined pressure by the compressor 2 and supplied to the cathode of the fuel cell 1 through the evaporator 3 and the air supply passage (oxidant supply passage) 21. After being supplied to the power generation, this air is discharged from the fuel cell 1 as a cathode off-gas, and is discharged through a cathode off-gas discharge passage 22 and a catalytic combustor (combustor, remover) 4. A fuel supply passage 23 that allows the fuel of the catalyst combustor 4 to be supplied is connected to the cathode offgas discharge passage 22 upstream of the catalyst combustor 4. Although the fuel of the catalytic combustor 4 is not particularly limited, it is preferable to use hydrogen as a fuel of the fuel cell 1 or alcohol for lowering the freezing point, which will be described later, because the system configuration becomes easy.
[0021]
The evaporator 3 is connected to an alcohol supply channel 24 that can supply alcohol as a chemical substance that lowers the freezing point of water. The evaporator 3 is connected to the evaporator 3 via an injector nozzle or the like from the alcohol supply channel 24. The supplied alcohol is evaporated, and the alcohol vapor is mixed with the air supplied from the compressor 2. In addition, as the alcohol, one of methanol, ethanol, propanol, ethylene glycol, and glycerin, or a mixture of two or more thereof, which has high solubility in water, can be used.
In this embodiment, the evaporator 3 and the alcohol supply channel 24 constitute freezing point depressant supply means.
[0022]
The catalytic combustor 4 is a heat source of the evaporator 3, catalytically burns the fuel supplied from the fuel supply channel 23 to the cathode off-gas, and supplies generated heat to the evaporator 3 as a heat source. Further, when alcohol remains in the cathode off-gas discharged from the fuel cell 1, the remaining alcohol is also catalytically burned in the catalytic combustor 4, so that the alcohol for freezing point lowering is removed from the cathode off-gas. Can be. Accordingly, the catalytic combustor 4 has both a function as a heat source of the evaporator 3 and a function as a remover for removing alcohol for freezing point lowering remaining in the cathode offgas.
[0023]
In the power generation system configured as described above, when the generated water generated by the power generation is likely to be frozen, for example, when the fuel cell 1 is started at a temperature below freezing (0 degrees Celsius or less) or when the fuel cell 1 is When the operation is stopped, a predetermined amount of alcohol is supplied to the evaporator 3 from the alcohol supply flow path 24, and a predetermined amount of fuel is supplied to the cathode offgas from the fuel supply flow path 23 (hereinafter, this processing is referred to as “antifreeze liquefaction”). Processing)).
[0024]
The fuel supplied to the cathode off-gas from the fuel supply channel 23 is catalytically combusted in the catalytic combustor 4, and the heat generated thereby is supplied to the evaporator 3, and supplied to the evaporator 3 from the alcohol supply channel 24. The alcohol evaporates. The alcohol evaporated in the evaporator 3 becomes alcohol vapor, is mixed with air pumped from the compressor 2, is supplied to the cathode of the fuel cell 1 through the air supply passage 21 together with the air, and is used for power generation. . The generated water is generated at the time of the power generation, but since the generated water contains alcohol, the freezing point of the generated water is lowered, and the generated water is lyophilized. As a result, freezing of the generated water is prevented.
[0025]
Therefore, if the antifreeze liquefaction process is executed immediately before the fuel cell 1 is stopped in a sub-zero temperature state, the generated water generated by the power generation is liquefied and prevented from freezing, and the fuel cell 1 is stopped when the fuel cell 1 is stopped. Even if the generated water remains, the remaining generated water does not freeze. As a result, it is possible to prevent the passage of the reaction gas (hydrogen or air) or the diffusion layer in the fuel cell 1 due to the freezing of the generated water from being blocked, and to improve the startability when the fuel cell 1 is started next time. I do.
[0026]
If the antifreeze liquefaction process is performed when the fuel cell 1 is started at a temperature below the freezing point, the generated water generated by the power generation after the start is liquefied and prevented from freezing. The blockage of the reaction gas flow path and the diffusion layer in the fuel cell 1 does not occur, and power generation can be continued.
In addition, a part of the alcohol supplied to the cathode causes an oxidation reaction on the cathode catalyst to generate heat and heat the vicinity of the power generation part, so that a low-temperature start time can be reduced.
In addition, since the alcohol supplied to the cathode is steam, the vicinity of the power generation portion of the fuel cell 1 can be heated by the sensible heat of the steam and the heat of condensation when the steam is condensed. The starting time can be reduced.
[0027]
The alcohol does not adversely affect the solid polymer electrolyte membrane of the fuel cell 1 and does not impair the power generation performance and the life.
Further, even when a part of the alcohol remains in the cathode off-gas discharged from the fuel cell 1, the remaining alcohol is catalytically burned in the catalytic combustor 4. Can be. In addition, since the heat obtained by burning the remaining alcohol is used as a part of the heat source of the evaporator 3, the alcohol supplied to the evaporator 3 can be effectively used.
In addition, the heat generated in the catalytic combustor 4 can heat the cooling water supplied to the fuel cell 1 or heat the hydrogen and air supplied to the fuel cell 1. The warm-up of the fuel cell 1 can be accelerated, and the low-temperature start time can be further reduced.
[0028]
The alcohol addition amount required in the antifreeze liquefaction process described above can be determined as follows.
The amount of generated water nw (mol / s) generated by power generation is calculated from the following equation based on the relationship with the extraction current I (A).
nw = I / 2 / F Expression (1)
In the equation (1), F is a Faraday constant.
Further, the takeout current has a correlation with the temperature of the fuel cell 1 and is determined by the characteristics of the fuel cell 1 to be used. FIG. 2 is a diagram showing an example of the relationship between the temperature of the fuel cell and the current that can be taken out.
[0029]
Therefore, assuming that the concentration of alcohol that does not freeze to a predetermined temperature is x (wt%) and the molecular weight of water is Mw, the required addition amount mm (g / s) is calculated from the following equation.
mm = Mw · nw · x / (100−x) (2)
The alcohol concentration that does not freeze is a concentration unique to the alcohol, which differs depending on the temperature and the type of the alcohol.
Therefore, when the type of alcohol is determined and the predetermined temperature at which the alcohol is not frozen is determined, a map for calculating the alcohol addition amount from the take-out current as shown in FIG. 3 can be created based on the equation (2). In the map of FIG. 3, the required addition amount is the addition amount calculated based on the equation (2), and the actual addition amount is the actually added amount, and the actual added amount is the required addition amount. Set slightly larger than.
[0030]
When the antifreeze liquefaction process is performed at the time of starting the fuel cell 1, as described above, a retrievable current is obtained from the temperature of the fuel cell 1 at the time of starting, and the actual addition amount of alcohol is determined based on the retrievable current. Ask.
On the other hand, when the antifreeze liquefaction process is executed when the fuel cell 1 is stopped, it is necessary to calculate the alcohol addition amount in advance based on the tendency of the temperature and current of the fuel cell 1 after the fuel cell 1 starts to change with time. Alternatively, a map created based on the measured data of the change with time is searched to determine the alcohol addition amount.
The map created based on the measured data of the temperature and current of the fuel cell 1 over time after the fuel cell 1 is started will be described in detail below.
[0031]
FIG. 4 shows a time-dependent change in the temperature and the current after the start when the temperature at the start of the fuel cell 1 is a certain temperature t of 0 ° C. or less. It has been experimentally confirmed that there is a similar tendency.
Therefore, a large number of temperatures at the time of starting are set, and changes over time of the temperature and the current as shown in FIG. 4 are obtained. For each of the temperatures at the time of starting, the integrated current value until the temperature reaches 0 degrees Celsius (FIG. 4, a map showing the relationship between the starting temperature and the current integrated value as shown in FIG. 5 is created.
Therefore, if the integrated current value is obtained by searching the map shown in FIG. 5 from the predicted starting temperature, the required addition amount can be calculated from the above equations (1) and (2).
[0032]
Next, antifreeze liquefaction control in this embodiment will be described with reference to the flowchart of FIG.
The antifreeze liquefaction control routine shown in the flowchart of FIG. 6 is executed by the ECU (not shown) at regular intervals.
First, in step S101, it is determined whether the operation mode of the fuel cell 1 is the start mode.
If the determination result in step S101 is “YES” (start mode), the process proceeds to step S102, and it is determined whether the temperature is lower than the first predetermined value t1. The temperature in this case can be any one of air temperature, water temperature, and fuel cell temperature, and the first predetermined value t1 is 0 degree Celsius or less.
If the determination result in step S102 is “NO” (temperature ≧ predetermined value t1), it is not necessary to perform the antifreeze liquefaction process, and thus the execution of this routine is temporarily terminated.
[0033]
If the determination result in step S102 is “YES” (temperature <first predetermined value t1), the process proceeds to step S103, and the alcohol addition amount (injection amount) according to the temperature is obtained by calculation or map search.
Next, proceeding to step S104, alcohol is injected into the evaporator 3 by the amount of alcohol added obtained in step S103.
Further, the process proceeds to step S105, a current corresponding to the temperature is taken out of the fuel cell 1, and the execution of this routine is temporarily terminated.
[0034]
On the other hand, if the determination result in step S101 is “NO” (other than the start mode), the process proceeds to step S106, and it is determined whether the operation mode of the fuel cell 1 is the stop mode.
If the determination result in step S106 is "NO" (other than the stop mode), it is not necessary to perform the antifreeze liquefaction process, and thus the execution of this routine is temporarily terminated.
If the determination result in step S106 is “YES” (stop mode), the process proceeds to step S107, and it is determined whether the temperature of the fuel cell 1 is lower than a second predetermined value t2. Note that the temperature in this case is the same as the temperature in step S102, and the second predetermined value t2 is 0 degree Celsius or less.
[0035]
Further, the magnitude relationship between the threshold value t1 in step S102 and the threshold value t2 in step S107 is not particularly limited, and any setting of t1 = t2, t1> t2, and t1 <t2 can be considered. Further, the temperature detection location to be compared with the threshold value t1 in step S102 may be different from the temperature detection location to be compared with the threshold value t2 in step S107. For example, the temperature to be compared with the threshold value t1 in step S102 is “engine temperature” detected by the temperature sensor attached to the fuel cell 1, and the temperature to be compared with the threshold value t2 in step S107 is The “intake air temperature” detected by the attached temperature sensor may be used.
[0036]
If the determination result in step S107 is “NO” (temperature ≧ predetermined value t2), it is not necessary to perform the antifreeze liquefaction process, and thus the execution of this routine is temporarily terminated.
If the result of the determination in step S107 is “YES” (temperature <second predetermined value), the process proceeds to step S108, and the alcohol addition amount (injection amount) according to the temperature is obtained by calculation or map search.
Next, proceeding to step S109, alcohol is injected into the evaporator 3 by the amount of alcohol added obtained in step S108.
Further, the process proceeds to step S110, in which the power generation system is stopped, and the execution of this routine is temporarily terminated.
[0037]
In this embodiment, the antifreeze liquefaction process is executed under both the start and stop of the fuel cell 1 under a predetermined temperature condition. However, the antifreeze liquefaction process is executed only in one of the cases. It is also possible. For example, when a process of discharging all generated water in the system when the power generation system is stopped is performed, the purpose is achieved by omitting the antifreeze liquefaction process at the time of the stop and executing the antifreeze liquefaction process only at the start. be able to. When the antifreeze liquefaction process is executed when the fuel cell 1 is stopped, and the alcohol addition amount required at the time of starting can be retained in the fuel cell 1 or the air supply passage 21, the antifreeze solution at the time of starting is The conversion process can be omitted.
[0038]
[Second embodiment]
FIG. 7 is a schematic configuration diagram of a power generation system according to the second embodiment.
The difference between the power generation system of the second embodiment and that of the first embodiment is that at least a part of the cathode offgas is discharged from the cathode offgas discharge passage 22 upstream of the connection with the fuel supply passage 23. Is provided in a cathode off-gas circulation flow path 25 that returns the air to the air supply flow path 21 upstream of the evaporator 3, and only the circulation pump 5 is provided in the cathode off-gas circulation flow path 25.
Other configurations are the same as those of the first embodiment, and therefore, the same reference numerals are given to the same aspects, and description thereof will be omitted.
[0039]
The system according to the second embodiment has the following operation in addition to the operation of the system according to the first embodiment.
In the second embodiment, by operating the circulation pump 5 during the execution of the antifreeze liquefaction process, a part or all of the cathode off-gas before the fuel of the catalytic combustor 4 is supplied is removed from the evaporator 3. The water is returned to the air supply flow path 21 upstream of the evaporator 3, thereby returning the generated water contained in the cathode offgas to the evaporator 3.
By doing so, the mixing of the alcohol and the produced water can be promoted, so that the freezing point drop of the produced water can be further promoted. In addition, when alcohol supplied for the purpose of lowering the freezing point remains in the cathode off-gas, the remaining alcohol can be circulated and reused for lowering the freezing point. The amount can be reduced.
[0040]
[Third Embodiment]
FIG. 8 is a schematic configuration diagram of a power generation system according to the third embodiment.
The difference between the power generation system of the third embodiment and that of the first embodiment is that the fuel cell 1 does not include the evaporator 3 and uses the alcohol for freezing point lowering supplied from the alcohol supply channel 24 to the fuel cell 1. The point is that the injector 6 directly injects the air into the air supply channel 21 near the cathode inlet. In this embodiment, the injector 6 and the alcohol supply flow path 24 constitute a freezing point depressant supply means.
Other configurations are the same as those of the first embodiment, and therefore, the same reference numerals are given to the same aspects, and description thereof will be omitted.
[0041]
According to the power generation system of the third embodiment as well, the antifreeze liquefaction process is executed immediately before the fuel cell 1 is stopped in a sub-zero temperature state, so that the generated water generated by power generation is antifreeze and prevented from freezing. Therefore, even when the operation of the fuel cell 1 is stopped, it is possible to prevent the passage of the reaction gas (hydrogen or air) or the diffusion layer in the fuel cell 1 from being blocked, and to start the fuel cell 1 the next time the fuel cell 1 is started. Performance can be improved.
[0042]
Also, by executing the antifreeze liquefaction process when the fuel cell 1 is started at a temperature below the freezing point, it is possible to antifreeze the generated water generated by the power generation after the start and prevent freezing. Blockage of the flow path and the diffusion layer does not occur, and power generation can be continued.
In addition, a part of the alcohol supplied to the cathode causes an oxidation reaction on the cathode catalyst to generate heat and heat the vicinity of the power generation part, so that a low-temperature start time can be reduced.
[0043]
[Other embodiments]
Note that the present invention is not limited to the above-described embodiment.
For example, in the above-described embodiment, the catalytic combustor is used as the heat source of the evaporator for evaporating the alcohol. However, the heat source may be a combustor that does not use a catalyst, or an electric heater or the like instead of the combustor. It is also possible to use.
[0044]
【The invention's effect】
As described above, according to the first aspect of the present invention, the chemical substance that lowers the freezing point of water is included in the generated water generated by power generation at the time of starting and / or stopping at a temperature of 0 degrees Celsius or less. Therefore, the freezing point of the produced water is lowered, and the freezing of the produced water can be prevented, so that an excellent effect that power generation can be continued even when the fuel cell is started below the freezing point is exhibited.
[0045]
According to the second aspect of the present invention, when there is a possibility that generated water generated by power generation may freeze, a chemical substance that lowers the freezing point of water can be supplied to the cathode of the fuel cell. Chemicals that lower the freezing point of water can be included in the water, and the freezing point of the generated water can be lowered to prevent freezing of the generated water.Therefore, power can be generated even when the fuel cell is started below the freezing point. An excellent effect of being able to continue is exhibited.
[0046]
According to the third aspect of the present invention, the vicinity of the power generation site can be heated by the sensible heat of the vapor of the chemical substance and the heat of condensation when the vapor condenses, so that the low-temperature start-up time can be shortened. effective.
According to the invention according to claim 4, there is an effect that a chemical substance having a freezing point drop remaining in the cathode offgas can be removed.
According to the fifth aspect of the present invention, there is an effect that the chemical substance having a lower freezing point remaining in the cathode off-gas can be burned and removed.
[0047]
According to the invention according to claim 6, the chemical substance having a freezing point depression remaining in the cathode off-gas can be removed by burning by the combustion means, and the freezing point depression by the heat generated by the combustion means in the evaporator. Since the chemical substance can be evaporated, there is an effect that the chemical substance can be effectively used.
According to the seventh aspect of the present invention, since the mixing of the freezing point lowering chemical substance and the generated water can be promoted, there is an effect that the freezing point lowering of the generated water can be further promoted. In addition, since the chemical substance having a lower freezing point remaining in the cathode off-gas can be circulated and reused, there is also an effect that the consumption of the chemical substance can be reduced.
[0048]
According to the invention of claim 8, since the chemical substance in an amount necessary for preventing freezing of the generated water can be reliably supplied to the cathode, the power generation of the fuel cell below the freezing point can be reliably continued. There is.
According to the ninth aspect of the present invention, there is an effect that freezing of generated water can be prevented without adversely affecting the solid polymer electrolyte membrane. In addition, since a part of the chemical substance composed of alcohols supplied to the cathode causes an oxidation reaction on the cathode catalyst to generate heat and heat the vicinity of the power generation site, there is also an effect of shortening the low-temperature start-up time.
[0049]
According to the tenth aspect, even when the generated water is likely to freeze, the generated water can be prevented from freezing, so that the low-temperature startability of the fuel cell is improved, and the fuel cell is started below the freezing point. An excellent effect that power generation can be continued even when the power is turned on is exhibited. .
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a power generation system according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a relationship between a fuel cell temperature and a current that can be taken out.
FIG. 3 is a map showing a relationship between a take-out current and an alcohol addition amount.
FIG. 4 is a diagram showing changes over time in temperature and current after starting a fuel cell.
FIG. 5 is a map showing a relationship between a starting temperature of a fuel cell and an integrated current value.
FIG. 6 is a flowchart showing antifreeze liquefaction control in the first embodiment.
FIG. 7 is a schematic configuration diagram of a power generation system according to a second embodiment of the present invention.
FIG. 8 is a schematic configuration diagram of a power generation system according to a third embodiment of the present invention.
[Explanation of symbols]
1 fuel cell
3 Evaporator (freezing point depressant supply means)
4 catalytic burners (burners, removers)
6. Injector (freezing point depressant supply means)
21 Air supply channel (oxidant supply channel)
24 Alcohol supply channel (freezing point depressant supply means)
25 Cathode off-gas circulation channel

Claims (10)

A power generation system comprising a fuel cell having an anode and a cathode on both sides of a solid polymer electrolyte membrane, fuel is supplied to the anode, and an oxidant is supplied to the cathode to generate power,
When the fuel cell is started and / or stopped at a temperature of 0 degrees Celsius or less, a chemical substance that lowers the freezing point of water is supplied to the cathode. A power generation system comprising a fuel cell having an anode and a cathode on both sides of a solid polymer electrolyte membrane, fuel is supplied to the anode, and an oxidant is supplied to the cathode to generate power,
An oxidant supply channel for supplying an oxidant to the cathode,
Freezing point depressant supply means for supplying a chemical substance that lowers the freezing point of water to the oxidant supply flow path,
A power generation system comprising: The power generation apparatus according to claim 2, wherein the freezing point depressant supply means includes an evaporator for evaporating the chemical substance, and supplies the chemical substance evaporated by the evaporator to an oxidant supply flow path. system. The power generation system according to claim 2, further comprising a removal unit configured to remove the chemical substance remaining in the cathode offgas discharged from the cathode. The power generation system according to claim 4, wherein the removal unit is a combustion unit that burns the chemical substance. 4. The method according to claim 3, further comprising a combustion unit capable of burning the chemical substance remaining in the cathode off-gas discharged from the cathode, wherein heat generated by the combustion unit is used as a heat source of the evaporator. Power generation system. The power generation system according to any one of claims 2 to 6, further comprising a cathode off-gas circulation flow path that returns at least a part of the cathode off-gas discharged from the cathode to the oxidant supply flow path. The power generation system according to any one of claims 1 to 7, wherein a supply amount of the chemical substance supplied to the cathode is set according to a temperature. The power generation system according to any one of claims 1 to 8, wherein the chemical substance comprises at least one of alcohols such as methanol, ethanol, propanol, ethylene glycol, and glycerin. A method for operating a fuel cell, comprising an anode and a cathode on both sides of a solid polymer electrolyte membrane, a fuel being supplied to the anode, an oxidant being supplied to the cathode, and power generation.
When the generated water generated by the power generation of the fuel cell is likely to freeze, a chemical substance that lowers the freezing point of water is supplied to the cathode to dissolve the chemical substance in the generated water, A method for operating a fuel cell, wherein the fuel cell is made into an antifreeze.

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