JP2005038637A - Fuel cell power generating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the system efficiency of a fuel cell power generating apparatus by restraining the lowering of the temperature of a cell-cooling water by preferentially utilizing recovered water as reforming water when supplying water from a recovered water tank to a cell cooling water system tank. <P>SOLUTION: The cell cooling water system tank 55a disposed on a cooling water circulation circuit of the fuel cell 1 is divided into a reforming water tank 55b and a cell-cooling water tank 55c. At the same time, a communication part 55d, through which the water in divided tanks is made to communicate, is formed at least at a part of the respective divided tanks. Water is guided from a recovered water tank 31 to the reforming water tank 55b, and the reforming water for a reforming device 3 is made to be guided from the reforming water tank 55b. Further, the cooling water for the fuel cell 1 is made to reflow into the cell-cooling water tank 55c after being guided out from the cell-cooling water tank 55c and flowing through the fuel cell. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a reformer that steam-reforms a hydrocarbon-based raw fuel gas into a hydrogen-rich gas by a catalyst, and condensate water by condensing steam in exhaust gas such as reformer combustion exhaust gas and fuel cell off-air. The present invention relates to a fuel cell power generator including a recovered water tank to be recovered.
[0002]
[Prior art]
There are various types of fuel cells incorporated in the fuel cell power generator, depending on the type of electrolyte, the type of reforming raw material, and the like. For example, a solid polymer membrane is used as the electrolyte, and the operating temperature is about 80 ° C. A solid polymer electrolyte fuel cell is well known as a relatively low type fuel cell.
[0003]
This solid polymer electrolyte fuel cell is similar to a phosphoric acid fuel cell, for example, in hydrogen and air in a fuel gas obtained by steam reforming a hydrocarbon-based raw fuel such as methane gas (city gas). Oxygen is supplied to the fuel electrode and the air electrode of the fuel cell, respectively, and electricity is generated based on the electrochemical reaction. Further, when reforming raw fuel into fuel gas, a method is adopted in which steam is added to the raw fuel and reforming is promoted by a catalyst in a fuel reformer (the basic system configuration is, for example, Patent Document 1).
[0004]
In order to perform the reforming constantly, it is necessary to constantly replenish the required amount of water vapor, and it is necessary to constantly replenish the water vapor supply device with water corresponding thereto. The water to be used needs to be high-purity water, and ion-exchanged water from which impurities have been removed by an ion-exchange type water treatment device is usually used.
[0005]
On the other hand, in the electrochemical reaction of the fuel cell, power generation product water is generated, and in the fuel reformer, combustion product water is generated with combustion for catalyst heating for performing a steam reforming reaction which is an endothermic reaction constantly. These generated waters have fewer impurities than normal tap water, and if these generated waters are used as raw water, the load on the water treatment device can be reduced. Therefore, a recovery water tank and an exhaust gas cooler are added. A method of recovering these generated waters to obtain supply water for generating reformed steam is usually employed.
[0006]
Further, in the electrochemical reaction of the fuel cell, heat is generated along with the reaction, and a part of the exhaust heat energy is stored as hot water in a hot water storage tank and supplied for hot water supply or heating.
[0007]
FIG. 4 is a system diagram showing an example of a conventional solid polymer electrolyte fuel cell power generation device using city gas as a raw fuel. Compared with that disclosed in Patent Document 1, battery cooling water system equipment and recovered water are shown. A more detailed system configuration is shown by adding devices and the like.
[0008]
In FIG. 4, a fuel cell 1 schematically shown includes a cooling plate 1c having a cooling pipe or a cooling groove (not shown) arranged and stacked each time a plurality of unit cells each having a fuel electrode 1a and an air electrode 1b are stacked. It is comprised by doing.
[0009]
The raw fuel (main component CH ₄ ) is first supplied to the reformer 3 together with the reforming steam, and is reformed to hydrogen and carbon monoxide by the following reaction. As the reforming catalyst, a noble metal catalyst or a nickel catalyst is used.
[0010]
CH ₄ + H ₂ O → 3H ₂ + CO (endothermic reaction)
Thereafter, the reformed gas is supplied to the CO converter 4, and the carbon dioxide in the reformed gas is reduced to about 1% by the following reaction. As the CO conversion catalyst, a noble metal catalyst or a copper-zinc catalyst is used.
[0011]
CO + H ₂ O → H ₂ + CO ₂ (exothermic reaction)
Thereafter, the carbon monoxide in the reformed gas is reduced to about 10 ppm by the following reaction that is further supplied to the CO remover 5 and selectively oxidizes CO with air supplied by a selective oxidation air blower (not shown). It is supplied to the fuel electrode 1a of the fuel cell.
[0012]
CO + 1 / 2O ₂ → CO ₂ (exothermic reaction)
As described above, when the reforming reaction is performed in the reformer 3, it is necessary to supply water vapor. In the polymer electrolyte fuel cell power generator, the sensible heat of the combustion exhaust gas from the reformer 3 and CO conversion are used as the heat source. In general, the heat of reaction of the vessel 4 and the CO remover 5 is used. Therefore, the reforming water supply line 25 for sequentially flowing the reforming water supplied by the battery cooling water circulation pump 54 through the reactors of the CO converter 4, the CO remover 5, and the steam generator 24 in series is provided. It is configured to receive heat from each of the reactors into steam, mix the steam and raw fuel, and introduce the steam into the reformer 3 from the reforming steam supply line 25. In FIG. 4, the reforming water flow line to the CO converter 4 and the CO remover 5 is omitted.
[0013]
In addition, since each of the reactors performs a chemical reaction using a catalyst, it is necessary to raise the temperature to an appropriate temperature in advance when the fuel cell power generator is started.
Appropriate temperatures for each reactor are as follows. Reformer: 500-700 ° C, CO converter: 200-300 ° C, CO remover: 100-250 ° C.
[0014]
For this reason, the reformer 3 is normally heated by burning the hydrogen supplied from the exhaust hydrogen supply line 19 of the fuel cell with a burner installed in the reformer. The temperature is raised by burning the raw fuel with a burner. In addition, the steam generator 24 is also heated by the combustion exhaust gas from the reformer. On the other hand, the CO transformer 4 and the CO remover 5 are heated by an electric heater (not shown) provided individually. Combustion air is introduced into the burner by a combustion air blower 6. Reference numeral 7 denotes a reaction air blower for supplying reaction air and CO selective oxidation air in a CO remover to the air electrode of the fuel cell main body.
[0015]
Further, the city gas is first introduced into the desulfurizer 2 by the city gas booster 27, and after the sulfur component contained in the city gas is removed, the city gas is introduced into the catalytic reactor of the reformer 3, and the combustion exhaust gas. As a result, the fuel gas is reformed while being supplied with heat, and becomes a hydrogen-rich fuel gas.
[0016]
Next, the cooling water system device 50 and the recovered water system device 30 of the fuel cell in FIG. 4 will be described below. The cooling water system device 50 includes a battery cooling water cooler 51, a cathode offgas cooler 52, an exhaust gas cooler 53 for combustion exhaust gas, a battery cooling water system tank (or pure water tank) 55, a battery cooling water circulation pump 54, and others. Including piping.
[0017]
The fuel cell 1 is operated at about 80 ° C. as described above, cooled by the water flowing from the pure water tank 55 by the battery cooling water circulation pump 54, and removed by the battery cooling water cooler 51. The battery cooling water cooler 51 is supplied with, for example, about 50 ° C. water supplied from a circulating water lead-out line 56 connected to a hot water storage tank (not shown in FIG. 4). Thereafter, the temperature is raised to, for example, about 60 ° C. via the cathode offgas cooler 52 and the exhaust gas cooler 53 for the combustion exhaust gas, and is returned to the hot water storage tank from the circulating water introduction line 57. The pure water tank 55 is provided with a liquid level gauge. When the liquid level reaches the lower limit, recovered water, which will be described later, is intermittently replenished via the water treatment device 35.
[0018]
Next, the recovered water system device 30 will be described. The recovered water system device 30 includes a recovered water tank 31, a recovered water pump 33, a recovered water cooler 34, and the like. Off-air and combustion exhaust gas cooled by the cathode off-gas cooler 52 and the combustion exhaust gas cooler 53 are introduced into the upper part of the recovered water tank 31, and the water content contained in the air and gas is sprinkled in the upper part. By condensing the cooling water from the apparatus, it is condensed and recovered in the lower part of the recovered water tank 31. The recovered water is cooled by the recovered water cooler 34 and introduced into the watering device. A cooling water direct contact type condenser having a packed bed such as a Raschig ring may be provided at the subsequent stage of the watering device.
[0019]
In this case, off-air containing steam and combustion exhaust gas are allowed to flow upward from the lower part of the packed bed (not shown in FIG. 4), while the recovered water at about 40 ° C. cooled by the recovered water cooler 34 is sprinkled from the upper part. Thus, the gas and the cooling water are brought into direct contact with each other in the packed bed portion, and the water and the water vapor in the gas are condensed and recovered, and there is an advantage that the recovery efficiency is improved with a simple structure.
[0020]
As described above, the recovered water is purified by a water treatment device and used as makeup water. A liquid level gauge is also provided at the bottom of the recovered water tank 31, and when the water in the recovered water tank is insufficient, city water (tap water) is supplied as make-up water. It is purified by.
[0021]
Next, FIG. 2 will be described. FIG. 2 is a system diagram showing an example of a conventional solid polymer electrolyte fuel cell power generator that is substantially similar in function to FIG. 4 but partially different, and is identical to the members shown in FIG. The functional members are assigned the same numbers and their detailed explanation is omitted.
[0022]
2, the main difference from the display in FIG. 4 is that in the cooling water circulation circuit of the fuel cell 1 including the battery cooling water system tank (or pure water tank) 55, the fuel cell cooling, which is not shown in FIG. The flow of reforming water to the CO remover 5 and the CO transformer 4, which is not shown in FIG. 4, as well as the three-way control valve 67 and the battery cooling water bypass line 60 a for adjusting the water inlet temperature. This is the point where a line is provided. In FIG. 2, the reforming water can generate steam in each of the coolers 5a and 4a of the CO remover 5 and the CO converter 4, and the steam generator 24 provided in the system diagram of FIG. 4 is omitted. ing.
[0023]
In FIG. 2, the battery cooling water cooler 51, the cathode offgas cooler 52, and the exhaust gas cooler 53 are shown in a distributed manner, unlike FIG. 4, but as in FIG. Are connected to a circulating water lead-out line 56 and a circulating water introduction line 57 that communicate with the circulating water.
[0024]
Next, an example of the conventional system shown in FIG. 3 will be described. The system shown in FIG. 3 shows an example of the system shown in FIG. 2 that focuses on the temperature adjustment of the battery cooling water. For convenience of explanation, some of the members are added or omitted. In FIG. 3, members having the same functions as those shown in FIG.
[0025]
In FIG. 3, the range indicated by the alternate long and short dash line 20 indicates the inside of the package of the polymer electrolyte fuel cell power generator. There are many devices inside the package 20 other than those shown in the figure, but they are omitted here.
[0026]
Reference numeral 1 denotes a fuel cell. As described above, the generated heat is supplied to the external hot water tank 70 by the battery cooling water cooler 51. At this time, the flow rate of the battery cooling water passing through the battery cooling water cooler 51 is appropriately adjusted so that the temperature detected by the battery cooling water temperature detector 66 becomes a temperature at which the fuel cell 1 can be stably operated by the three-way control valve 67. It is adjusting. The heat supplied to the outside by the battery coolant cooler 51 is stored in the hot water tank 70 by the hot water tank circulating water sent out by the hot water tank circulating water pump 69.
[0027]
When the hot water tank circulating water temperature detector 68 detects that the temperature level of the hot water tank 70 has reached a certain value or more, the hot water tank circulating water cooler 71 is activated and the battery cooling water temperature control of the fuel cell power generator is normal. It is controlled so that it can be performed. Note that the hot water tank circulating water is led out from the lower part of the hot water tank 70, heated by the battery cooling water cooler 51, and then supplied to the upper part of the hot water tank. This is considered as high as possible in the user hot water supply 76 using the hot water in the hot water tank, considering the temperature distribution of the hot water in the hot water tank 70 due to natural convection, that is, the temperature level of the upper layer in the hot water tank 70 is high. This is to supply a level of temperature.
[0028]
On the other hand, during the startup process until the fuel cell power generation device generates power, the battery cooling provided in the battery cooling water system tank 55 is used to raise the temperature of the fuel cell 1 to a predetermined temperature in preparation for the start of power generation. The battery cooling water is heated by the water heating heater 64. At this time, the flow path of the battery cooling water is set so as to bypass the battery cooling water cooler 51 by the three-way control valve 67 so as not to miss the heat of the battery cooling water that has been heated.
[0029]
In FIG. 3, 60 is a battery cooling water circulation circuit, 60 a is a battery cooling water bypass line, 80 is a hot water circulation circuit inside the hot water tank, and 77 is used to maintain the liquid level of the hot water tank 70 within a predetermined range. The on-off valve of city water supplied according to the amount of hot water used at the user hot water supply port 76 is shown.
[0030]
[Patent Document 1]
JP 2002-124288 A (page 2-3, FIG. 4)
[0031]
[Problems to be solved by the invention]
Incidentally, the conventional fuel cell power generator as shown in FIGS. 2 to 4 has the following problems.
[0032]
As shown in FIG. 2 described above, the cooling water circulation circuit of the fuel cell is provided with a battery cooling water system tank 55, and water is supplied from the recovered water tank 31 to the battery cooling water system tank 55, and from the battery cooling water system tank 55, The cooling water is supplied to the fuel cell 1 and the reforming water is supplied to the reformer 3.
[0033]
Usually, the water temperature in the battery cooling water system tank 55 is about 82 ° C., and the water temperature in the recovered water tank 31 is about 55 ° C., so that it is supplied when water is supplied from the recovered water tank 31 to the battery cooling water system tank 55. Although a part of the water is mixed in the tank and used as reforming water, there is a problem that the water temperature in the battery cooling water system tank 55 is lowered by the mixing.
[0034]
Therefore, in order to favorably cool the fuel cell and perform stable operation of the fuel cell, it is necessary to heat the cell cooling water heater 64 shown in FIG. 3 in order to compensate for the temperature drop. This causes a problem that the system efficiency is lowered.
[0035]
The present invention has been made in view of the above problems, and the object of the present invention is to preferentially use recovered water as reforming water when water is supplied from the recovered water tank to the battery cooling water system tank. Thus, it is intended to suppress the temperature drop of the battery cooling water and thereby improve the system efficiency of the fuel cell power generator.
[0036]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, in the present invention, a reformer having a reforming catalyst layer for steam reforming a hydrocarbon-based raw fuel, and a burner for heating the reforming catalyst with combustion exhaust gas, A fuel cell which generates electricity by an electrochemical reaction between fuel gas obtained by steam reforming and air and is cooled by cooling water in a circulation circuit, water vapor contained in the fuel cell off-air, and the burner A recovery water tank that condenses water vapor in the combustion exhaust gas in the fuel cell to recover the condensed water, and a battery cooling water system tank provided in the cooling water circulation circuit of the fuel cell, and water is supplied from the recovery water tank to the battery cooling water system tank. A fuel cell power generator configured to supply cooling water to the fuel cell from the battery cooling water system tank and to supply reforming water to the reformer. The battery cooling water system tank is divided into a reforming water tank and a battery cooling water tank, and at least a part thereof is provided with a communication part that allows the water in both of the divided tanks to communicate with each other. Water is introduced from the water tank to the reforming water tank, the reforming water to the reformer is led out from the reforming water tank, and the cooling water to the fuel cell is the battery cooling water. It is assumed that the battery is led out from the fuel tank and passed through the fuel cell, and then returned to the battery cooling water tank for introduction (claim 1).
[0037]
With the above configuration, when water is supplied from the recovered water tank to the battery cooling water system tank, the recovered water is introduced into the reforming water tank so that it can be preferentially used as the reforming water. Therefore, the temperature drop of the battery cooling water is suppressed, and the system efficiency of the fuel cell power generator can be improved.
[0038]
As an embodiment of the invention of claim 1, the inventions of claims 2 to 3 below are preferable. That is, in the fuel cell power generator according to claim 1, the communication part is provided at the bottom of the two tanks, and the water introduction and discharge parts of the two tanks are opposed to the communication part in the two tanks. It is assumed that it is provided on the side to be used (invention of claim 2).
[0039]
Furthermore, in the fuel cell power generator according to claim 1 or 2, the battery cooling water tank is provided with a battery cooling water heating heater (invention of claim 3). The heater for raising the temperature of the battery cooling water can be provided in another place in the cooling water circulation circuit of the fuel cell, but communicates with the reforming water tank into which recovered water having a temperature lower than the battery cooling water temperature is introduced. It is reasonable to provide it in the battery cooling water tank provided.
[0040]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the present invention will be described below with reference to the drawings.
[0041]
FIG. 1 is a schematic system diagram of a fuel cell power generator according to an embodiment of the present invention, and a part of the system on the left side of the system diagram shown in FIG. 2 is omitted.
[0042]
The difference between FIG. 1 and FIG. 2 is that in FIG. 1, as described above, the battery cooling water tank 55a is divided into the reforming water tank 55b and the battery cooling water tank 55c, and the divided Further, a communication portion 55d for communicating the water in both tanks is provided, water is introduced from the recovered water tank 31 to the reforming water tank 55b, and the reforming water to the reformer 3 is the reforming water tank 55b. Further, the cooling water to the fuel cell 1 is led out from the battery cooling water tank 55c and flows into the fuel cell, and then returns to the battery cooling water tank 55c. Is a point.
[0043]
The communication portion 55d is provided at the bottom of the two tanks, and the water introduction and discharge portions of both tanks are provided on the side facing the communication portion 55d in both tanks. Further, the battery cooling water tank 55c includes a battery cooling water heating heater 64.
[0044]
According to the above configuration, when water (for example, 55 ° C.) is supplied from the recovered water tank 31 to the battery cooling water system tank 55a, the recovered water is introduced into the reforming water tank 55b, and the reforming water tank 55b. From below, the reforming water is passed through the CO remover 5 and the respective coolers 5a and 4a of the CO converter, so that the recovered water has priority with little mixing with the battery cooling water (for example, 81 ° C.). It is used as reforming water. Therefore, the temperature drop of the battery cooling water is suppressed, and the system efficiency of the fuel cell power generator can be improved. Further, when the temperature of the battery cooling water is lowered to a predetermined temperature due to some mixing, the battery cooling water heating heater 64 can be turned on to immediately heat the battery cooling water.
[0045]
【The invention's effect】
As described above, according to the present invention, a reformer having a reforming catalyst layer for steam reforming a hydrocarbon-based raw fuel, a burner for heating the reforming catalyst with combustion exhaust gas, and the steam reforming process. A fuel cell that generates electricity by an electrochemical reaction between the fuel gas and air obtained in this way and cools with cooling water in the circulation circuit, and water vapor contained in the off-air of the fuel cell and combustion exhaust gas in the burner A recovery water tank that condenses the water vapor and recovers the condensed water, and a battery cooling water system tank provided in the cooling water circulation circuit of the fuel cell, and supplies water from the recovery water tank to the battery cooling water system tank, In the fuel cell power generator configured to supply cooling water to the fuel cell from the battery cooling water system tank and supply reforming water to the reformer, the battery cooling water system tank The tank is divided into a reforming water tank and a battery cooling water tank, and at least a part thereof is provided with a communication portion that allows the water in the two divided tanks to communicate with each other. Water is introduced into the reforming water tank, the reforming water to the reformer is led out from the reforming water tank, and the cooling water to the fuel cell is supplied from the battery cooling water tank. Since it was derived and passed through the fuel cell, it was configured to be refluxed and introduced into the battery cooling water tank.
When water is supplied from the recovered water tank to the battery cooling water system tank, the recovered water can be used preferentially as reforming water to suppress the temperature drop of the battery cooling water, thereby improving the system efficiency of the fuel cell power generator. Improvements can be made.
[Brief description of the drawings]
FIG. 1 is a schematic system diagram of a fuel cell power generator according to an embodiment of the present invention. FIG. 2 is a schematic system diagram of an example of a conventional fuel cell power generator. FIG. FIG. 4 is a schematic system diagram showing an example of a conventional fuel cell power generator. FIG. 4 is a schematic system diagram showing an example of a fuel cell power generator different from the conventional FIG.
1: fuel cell, 3: reformer, 4: CO converter, 5: CO remover, 31: recovered water tank, 55, 55a: battery cooling water tank, 55b: reforming water tank, 55c: battery cooling water Tank, 55d: communication part, 64: heater for battery cooling water temperature rising.

Claims (3)

A reformer having a reforming catalyst layer for steam reforming a hydrocarbon-based raw fuel, a burner for heating the reforming catalyst with combustion exhaust gas, and a fuel gas obtained by steam reforming and air Condensed water is recovered by condensing the water vapor contained in the fuel cell off-air and the water vapor contained in the combustion exhaust gas in the burner, which is generated by electrochemical reaction and cooled by the cooling water in the circulation circuit. A recovered water tank, and a battery cooling water system tank provided in a cooling water circulation circuit of the fuel cell, supplying water from the recovered water tank to the battery cooling water system tank, and from the battery cooling water system tank to a fuel cell In the fuel cell power generator configured to supply cooling water to the reformer and to supply reforming water to the reformer,
The battery cooling water system tank is divided into a reforming water tank and a battery cooling water tank, and at least a part thereof is provided with a communication part that allows water in the divided tanks to communicate with each other.
Water is introduced from the recovered water tank to the reforming water tank, the reforming water to the reformer is led out from the reforming water tank, and the cooling water to the fuel cell is the battery. A fuel cell power generator, wherein the fuel cell power generator is configured to be led out from the cooling water tank and flowed to the fuel cell and then to be recirculated and introduced into the battery cooling water tank. 2. The fuel cell power generation device according to claim 1, wherein the communication portion is provided at a bottom portion of the two tanks, and a water introduction / extraction portion of the two tanks is a side of the two tanks facing the communication portion. A fuel cell power generator provided in the above. 3. The fuel cell power generator according to claim 1, wherein the battery cooling water tank includes a battery cooling water heating heater. 4.

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