JP2005203361A - Fuel cell system, and its operating method, program, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system and its operation method in which the fuel cell system can surely keep the whole region of an MEA in steam saturation. <P>SOLUTION: The fuel cell system is provided with a stack 1 having a gas distribution means for introducing a reactant gas into the electrode of each unit cell, gas supply sections 2 and 3 for supplying the reactant gas to the stack 1, gas humidifying sections 4 and 5 disposed between the gas supplying member 2 and the electrode entrance of the gas distribution means for humidifying the reactant gas, and a controller for controlling the amount of steam contained in the reactant gas supplied to at least one of the electrodes to be larger than the amount of the saturated steam at a temperature at the entrance of at least one of the electrodes of the gas distribution means. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell system and an operation method thereof.

  A polymer electrolyte fuel cell is produced by exposing a fuel gas to one side of a polymer electrolyte membrane and an oxidant gas such as air to the other and synthesizing water by a chemical reaction via an ion exchange membrane. The basic principle is to extract reaction energy electrically.

  The basic power generation element of this fuel cell includes a polymer electrolyte membrane that selectively transports hydrogen ions, and a pair of carbon powders that are formed on both sides of the polymer electrolyte membrane and that carry a platinum group metal catalyst and that have carbon powder as a main component. A catalyst layer (an anode catalyst layer and a cathode catalyst layer) is provided. In addition, a gas diffusion electrode mainly composed of carbon fibers having both air permeability and electronic conductivity located between the pair of catalyst layers is provided. The polymer electrolyte membrane, the pair of catalyst layers, and the gas diffusion electrode are collectively referred to as an electrolyte membrane-electrode assembly. Hereinafter, the electrolyte membrane-electrode assembly is referred to as MEA (membrane-electrode-assembly).

  In addition, this fuel cell includes a sealing gasket disposed around the electrode of the MEA so as to sandwich the polymer electrolyte membrane. These MEA-gasket assemblies are sandwiched and fastened by an anode separator (conductive bipolar plate) in which a fuel gas channel is formed and a cathode separator in which an oxidant gas channel is formed. The anode separator is electrically connected to the cathode separator through an external circuit.

  In this system, when a fuel gas (usually hydrogen gas) is supplied to the anode separator and an oxidant gas (usually air) is supplied to the cathode separator, the following chemical reaction occurs.

  That is, the fuel gas passes through the anode gas diffusion electrode, reaches the anode catalyst layer, and dissociates into protons and electrons in the anode catalyst layer. At this time, the dissociated electrons are collected by the anode separator via the anode gas diffusion electrode. One proton is transported by the ion exchange membrane and moves to the cathode catalyst layer.

  In the cathode catalyst layer, this proton, the oxidant gas that has passed through the cathode gas diffusion electrode and reached the cathode catalyst layer, moved to the cathode separator through the external connection circuit, and then supplied to the catalyst layer via the cathode gas diffusion electrode A catalytic reaction occurs with the generated electrons, and water is generated.

  The principle of operation of the polymer electrolyte fuel cell is to electrically extract the energy difference when hydrogen is combined with oxygen to become water by the above series of reactions.

  Here, since the ion exchange membrane has a stable proton transport ability in a sufficiently wet state, water is required for the operation of this battery. This water is usually supplied simultaneously with the reaction gas by humidifying the hydrogen and air supplied to the cell. In addition, in order to perform the above reaction satisfactorily, a temperature of at least 60 ° C. is necessary. In practice, the fuel cell is often operated at 60 ° C. to 80 ° C.

  The electromotive force of the unit cell composed of the MEA and the separator depends on the output current density, but it is about 0.6 to 0.8 V in the normal usage range. This stacked battery is called a stack.

  In addition, the fuel cell generates heat simultaneously with power generation. However, since the heat generation density of the stack is larger than that of a single cell, a cooling water flow path is usually provided for every 1 to 3 cells to force water cooling (ethylene glycol). Etc.) and maintain the battery in a good temperature state. Therefore, three types of fluids, fuel gas, oxidant gas, and water, are supplied and discharged in the stack, and the separator has a pair of manifolds (a plurality of cases depending on the case) for each of the three types of fluids (common through holes). Is provided. Each of these fluids is connected to the grooves of the respective separators from the manifold, and is branched to each cell and the water cooling unit.

  For example, in the case of fuel gas, it is branched from the fuel gas supply manifold to the fuel gas flow path of the anode separator, and is consumed along with the cell reaction in the MEA in the process of flowing through the flow path, and surplus fuel gas is discarded to the fuel gas exhaust manifold. Is done. These cells (battery parts) and cooling parts are stacked one after the other, and the stacked body is sandwiched between end plates via current collector plates and insulating plates, and fixed from both ends with fastening bolts. It is the structure of a fuel cell.

  The fuel cell system refers to the entire apparatus for operating the stack to extract electric power. In this system, the stack is driven directly by hydrogen reforming available fuel such as LPG and LNG gasoline by steam reforming. The fuel gas supply system that supplies the stack to the stack, the oxidizing gas supply system that humidifies the air sent from the blower and supplies the stack, the cooling water system that supplies the circulating cooling water to the stack, and the electrical load that loads the power It is a system.

  The humidification necessary for the fuel gas is usually provided by water added to the fuel by the steam reforming method. In addition, in order to effectively use the generated water discharged from the stack, the humidification of air is usually performed by exchanging the cathode exhaust gas (wet air) with the supply air sent from the blower to obtain the desired humidification amount. It is. However, when the water added in the reforming reaction is insufficient with respect to the battery operating conditions, and when the water obtained by total heat exchange is insufficient with respect to the battery operating conditions, the stack cooling wastewater is placed downstream of these. A membrane humidifier is provided as a water source and heat source. Membrane humidification and total heat exchange are usually performed through a humidified membrane that allows water to easily permeate but does not allow gas to permeate. The ion exchange membrane (perfluorosulfonic acid membrane) used in the stack is this. It is suitable for use and is commonly used.

  Patent Document 1 is the most typical prior example of desirable operating conditions of the polymer electrolyte fuel cell and means for realizing the same. This point is listed below as the first prior art.

  A fuel cell is a device that generates water by electrochemically reacting hydrogen and oxygen to extract the potential difference as electric power. The generated water causes flooding of the catalyst layer (a phenomenon in which power generation is stopped when the catalyst layer is blocked with water and gas permeation is hindered), so this exclusion is extremely important for stable operation of the battery.

  The most effective method for eliminating the water produced at the cathode is to keep the fuel gas or oxidant gas at a water vapor amount below the saturation dew point. That is, by maintaining the amount of water vapor below the saturation dew point in the oxidant gas, the generated water evaporates into the oxidant gas, leaving room for discharge from the cell simultaneously with the excess oxidant gas. Also, since the ion exchange membrane easily permeates water, by keeping the fuel gas at a water vapor pressure below the saturation dew point, the water produced at the cathode reversely diffuses through the ion exchange membrane and then transpires into the fuel gas. The excess fuel gas can be discharged at the same time.

  A specific means for realizing the above operating condition is to give a pressure loss (pressure drop) between the gas suction part and the gas discharge part. In other words, since the water absorption capacity of gas increases as the pressure decreases, the water pressure generated in the cell in succession for the first time can be effectively eliminated by making the gas pressure lower as it goes to the discharge section. Is possible. Such pressure drop includes (a) an orifice provided in the suction portion, (b) an extension of the channel length, (c) a change in the channel cross-sectional area, (d) an increase in the friction coefficient of at least a part of the inner surface of the channel, (E) The flow rate of the hydrogen gas in the flow path is embodied by setting it substantially higher than the amount of hydrogen gas converted into cations at the anode. The gist of Patent Document 1 has been described above.

    However, the present inventor has a fatal defect in the above operating conditions particularly in applications where rated operation is performed at a low current density in order to emphasize the power generation efficiency of the stack (particularly in low-level cogeneration systems). I found That is, if both the fuel gas and the oxidant gas do not maintain the saturated water vapor amount for all the parts in the cell, the ion exchange membrane is damaged over time at the portion where the saturated water vapor amount is not maintained, and the fuel cell It means that the life cannot be maintained.

  An example of a fuel cell system that can eliminate the fatal defect of the first prior art and can maintain the life of the fuel cell will be described below as a second prior art.

  A second conventional fuel cell power generation system includes a polymer electrolyte fuel cell having a stack in which unit cells are stacked, an anode gas supply unit that supplies fuel gas to the polymer electrolyte fuel cell, and an oxidant gas. A cathode gas supply unit for supplying the gas. The anode gas supply unit has a reformer for reforming the fuel gas precursor to a hydrogen-rich fuel gas.

  Between the second prior art polymer electrolyte fuel cell and the anode gas supply unit, an anode gas humidification unit for humidifying the anode gas is installed. Further, a cathode gas humidification unit for humidifying the cathode gas is installed between the polymer electrolyte fuel cell and the cathode gas supply unit. These anode gas humidification section and cathode gas humidification section are based on a total heat exchanger for supplying the anode gas and cathode gas with exhaust heat and moisture of the anode and cathode exhaust gas discharged from the polymer electrolyte fuel cell. If necessary, a membrane humidifier using the stack cooling wastewater as a heat source and a water source is attached.

In the fuel cell power generation system of the second prior art having the above-described configuration, the temperature of the humidifying unit is maintained at a predetermined temperature based on the operating temperature of the stack, and the dew points of the anode gas and the cathode gas are adjusted. As a result, condensation occurs inside the stack. As a result, the solid polymer electrolyte membrane in the MEA contains necessary and sufficient moisture. That is, according to the fuel cell power generation system of the second prior art, flooding of the catalyst layer can be avoided and sufficient water can be contained in the solid polymer electrolyte membrane.

Thus, by using the fuel cell power generation system of the second prior art, the solid polymer electrolyte membrane can contain a sufficient amount of moisture, so that low current density is particularly important in order to emphasize the power generation efficiency of the stack. It is possible to solve the problem that the life of the fuel cell cannot be maintained in applications (especially low-level cogeneration systems) that are rated for operation.
JP-T 6-504403

  As described above, the fuel cell power generation system according to the second prior art is a fuel cell even in applications (especially low-level cogeneration systems) that are rated and operated at a low current density in order to emphasize the power generation efficiency of the stack. It is possible to solve the problem that the life of the product cannot be maintained. However, the fuel cell power generation system according to the second prior art causes the solid polymer electrolyte membrane to contain necessary and sufficient moisture when the fuel cell system is in an unbalanced state that is unavoidable in operation, that is, when starting and stopping and when the load fluctuates. As a result, the fuel cell cannot be protected.

    That is, in the second prior art humidification system (anode gas humidification unit and cathode gas humidification unit), the humidification heat source is primarily discharged from the reforming reaction water and secondarily from the stack at the anode. Waste anode gas (hereinafter referred to as “off gas”) and stack cooling wastewater, and at the cathode, primarily waste exhaust gas (hereinafter referred to as “off air”) discharged from the stack, and secondarily as stack cooling wastewater.

    When the load fluctuates, especially when the load is reduced, the temperature of the stack cooling drainage tends to decrease. This is because the calorific value is reduced at a low load and the heat dissipating element is relatively large, and the operating principle of the fuel cell improves the power generation efficiency in the low-load operation, resulting in a decrease in the calorific value. This is a phenomenon caused by the fact that it is difficult to control the amount of cooling water at low load (it is difficult to reduce the flow rate) with a normal rotary pump. Similarly, off-gas and off-air cannot obtain a sufficient amount of heat due to a heat dissipation factor when the load is low. As a result, due to the operating principle of the total heat exchanger or the membrane humidifier, sufficient humidification as described above becomes difficult due to a decrease in water temperature. The same applies to the stop operation.

    In addition, when the load is suddenly increased, the battery immediately requires water in proportion to the load, whereas the thermal element of the humidification system and the fuel supply system has a thermal time constant derived from the heat capacity. Exists, and cannot keep up with this request, so it becomes temporarily in a state of insufficient humidification.

    In particular, when the steam reforming method is used, the reformed gas dew point tends to overshoot at the time of startup. As a result, when the excessively humidified reformed gas is introduced into the fuel cell, the above-mentioned flooding is likely to occur, and when the load is taken as it is, the cell can be destroyed due to inversion.

    Due to these factors, the polymer electrolyte fuel cell system according to the second prior art has a problem that the battery deterioration rate is larger than the continuous rated operation when frequent start / stop and sudden load fluctuations are performed. It was happening.

  An object of the present invention is to provide a fuel cell system, an operation method of the fuel cell system, a program, and a recording medium that can more reliably maintain the entire MEA region in water vapor saturation in consideration of the above-described conventional problems. It is what.

In order to solve the above-described problems, the first aspect of the present invention provides an electrolyte membrane, a pair of gas diffusion electrodes arranged so as to sandwich the electrolyte membrane, and a pair of gas diffusion electrodes sandwiched from outside the pair of gas diffusion electrodes. A stack having a plurality of stacked unit cells, each having a separator formed with a gas channel groove for supplying fuel gas or oxidant gas to each of the gas diffusion electrodes;
A gas supply unit for supplying the gas to the stack;
A gas humidifying unit for humidifying the gas disposed between the gas supply unit and the gas flow channel groove;
The amount of water vapor contained in the gas supplied to the gas flow channel groove is more than the saturated water vapor amount at the temperature of at least one gas flow channel groove inlet portion of the gas diffusion electrode where the gas is first consumed. It is a fuel cell system provided with the control part which controls so that it may increase.

  The second aspect of the present invention is the fuel cell system according to claim 1, wherein the control unit controls the amount of water vapor contained in the gas so that the water vapor contained in the gas does not cause flooding in the electrolyte membrane. .

In the third aspect of the present invention, the control unit is provided between the gas flow channel groove and the gas humidification unit, and adjusts the water vapor amount of the gas supplied to the plurality of stacked unit cells. A buffer mechanism for performing,
The buffer mechanism is
A stockpiling unit that stocks moisture;
A heating unit for heating moisture stored in the storage unit;
A temperature detection unit for detecting the temperature of the stored water;
Supplying the moisture to be re-vaporized and supplied to the at least one electrode by controlling the heating unit so that the temperature of the moisture is kept higher than the temperature at the electrode entrance of the gas flow channel groove The fuel cell system according to claim 1, further comprising a control unit.

According to a fourth aspect of the present invention, there is provided an electrolyte membrane, a pair of gas diffusion electrodes disposed so as to sandwich the electrolyte membrane, and a fuel gas or an oxidation gas disposed between the outside of the pair of gas diffusion electrodes. A stack having a plurality of stacked unit cells having a separator in which a gas flow channel for supplying agent gas to each of the gas diffusion electrodes is formed;
A gas supply unit for supplying the gas to the stack;
A gas humidifying unit for humidifying the gas disposed between the gas supply unit and the gas channel groove;
A fuel cell system comprising: a buffer mechanism unit that is provided between the gas flow channel groove and the gas humidifying unit and adjusts a water vapor amount of the gas supplied to the plurality of stacked unit cells; is there.

Further, the fifth aspect of the present invention is that the buffer mechanism section includes a storage section that stores water,
A heating unit for heating moisture stored in the storage unit;
A temperature detection unit for detecting the temperature of the stored water;
Control the heating unit so that the temperature of the moisture is kept higher than the temperature at the electrode entrance of the gas flow channel groove, and re-vaporize the moisture to supply the moisture to the at least one electrode The fuel cell system according to claim 4, further comprising: a unit.

Further, the sixth aspect of the present invention performs the heat amount control for condensing the water vapor supplied from the gas supply unit beyond the saturated water vapor amount at the internal temperature of the buffer mechanism unit,
The controller is
(1) Waste heat of reformer (2) Heat of fuel gas supplied from reformer to stack (3) Heat obtained by burning fuel (4) Residual exhaust from stack Heat obtained by burning fuel gas
(5) The fuel cell according to claim 5, wherein the condensed water vapor is vaporized by using at least one of heats of waste water of the cooling water discharged from the stack as a heat source. System.

  The seventh aspect of the present invention is the fuel cell system according to claim 6, wherein the heat obtained by burning the fuel or the remaining fuel gas discharged from the stack is obtained from a reformer burner.

  The fuel according to claim 6, wherein the heat obtained by burning the fuel or the remaining fuel gas discharged from the stack is obtained from a dedicated combustor other than a reformer burner. It is a battery system.

  In the ninth aspect of the present invention, the control unit performs heat amount control of the one or more heats to be introduced into the buffer mechanism unit based on a detection signal for detecting the amount of water vapor supplied to the stack. The amount of water vapor contained in the gas supplied to the gas flow channel groove is larger than the saturated water vapor amount at the temperature at the gas flow channel groove inlet portion where the gas is first consumed in the gas diffusion electrode. The fuel cell system according to claim 6, wherein the fuel cell system is controlled.

  The tenth aspect of the present invention is the fuel cell system according to claim 9, wherein the control unit performs heat amount control of the one or more heats by controlling a heat medium amount.

  The eleventh aspect of the present invention is the fuel cell system according to claim 9, wherein the heat amount control of the one or more heats by the control unit includes a combustion amount control of the reformer or a dedicated combustor.

  The twelfth aspect of the present invention is the fuel according to claim 6, wherein the supply of the one or more heats to the control unit is performed by direct conduction of a thermal fluid from a heat source of the heat. It is a battery system.

  Further, in the thirteenth aspect of the present invention, the supply of the one or more heats to the control unit is performed by indirect conduction performed after the heat fluid from the heat source of the heat exchanges heat with the stack cooling drainage. It is a fuel cell system of Claim 6 performed.

  The fourteenth aspect of the present invention is the fuel cell system according to claim 4, wherein a plurality of control constants of the control unit can be set corresponding to a plurality of operation modes.

  Further, the fifteenth aspect of the present invention is the fuel cell system according to claim 4, wherein the control unit learns and controls an optimal control constant in a use situation.

The sixteenth aspect of the present invention includes a gas inlet manifold for supplying the gas to the gas flow channel groove,
5. The fuel cell system according to claim 4, wherein the buffer mechanism portion is disposed in direct connection with the gas inlet manifold.

The seventeenth aspect of the present invention includes a gas inlet manifold for supplying the gas to the gas passage groove,
The fuel cell system according to claim 4, wherein the buffer mechanism is provided in the gas inlet manifold.

  The eighteenth aspect of the present invention is the fuel cell system according to claim 4, wherein the stack and the buffer mechanism are collectively insulated.

According to a nineteenth aspect of the present invention, there is provided an electrolyte membrane, a pair of gas diffusion electrodes disposed so as to sandwich the electrolyte membrane, and a fuel gas or an oxidation gas disposed between the pair of gas diffusion electrodes. A stack having a plurality of stacked unit cells having a separator in which a gas flow channel for supplying agent gas to each of the gas diffusion electrodes is formed;
A gas supply unit for supplying the gas to the stack;
A fuel cell system operating method for operating a fuel cell system comprising a gas humidifying unit for humidifying the gas disposed between the gas supply unit and the gas flow channel groove,
The amount of water vapor contained in the gas supplied to the gas flow channel groove is larger than the saturated water vapor amount at the temperature at the gas flow channel groove inlet portion where the gas is first consumed in the gas diffusion electrode. This is a method for operating a fuel cell system, which includes a control step for performing control as described above.

The twentieth aspect of the present invention is an electrolyte membrane, a pair of gas diffusion electrodes disposed so as to sandwich the electrolyte membrane, and a fuel gas or oxidation gas disposed between the outside of the pair of gas diffusion electrodes. A stack having a plurality of stacked unit cells having a separator in which a gas flow channel for supplying agent gas to each of the gas diffusion electrodes is formed;
A gas supply unit for supplying the gas to the stack;
An operation method of a fuel cell system, comprising a gas humidifying unit for humidifying the gas disposed between the gas supply unit and the gas flow channel groove,
It is an operating method of a fuel cell system provided with the adjustment step which adjusts the amount of water vapor of the gas supplied to the plurality of laminated unit cells between the gas channel groove and the humidification part.

  According to a twenty-first aspect of the present invention, in the fuel cell system according to claim 1, the amount of water vapor contained in the gas supplied to the gas flow channel groove is a place where the gas is first consumed in the gas diffusion electrode. This is a program for causing a computer to function as a control unit that performs control so as to increase the amount of saturated water vapor at the temperature at the gas channel groove inlet.

    The twenty-second aspect of the present invention is a recording medium on which the program according to the twenty-first aspect is recorded, and is a recording medium that can be processed by a computer.

  According to the present invention, it is possible to provide a fuel cell system, a fuel cell system operating method, a program, and a recording medium that can more reliably keep the entire MEA region in water vapor saturation.

    Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a conceptual diagram of the basic configuration of the fuel cell system of the present invention in the first embodiment. The polymer electrolyte fuel cell system according to the first embodiment includes a stack 1 in which unit cells are stacked, an anode gas supply unit 2 that supplies fuel gas to the stack 1, and a cathode gas supply unit 3 that supplies oxidizing gas. And. Between the stack 1 and the anode gas supply unit 2, an anode gas humidification unit 4 for humidifying the anode gas is installed. Further, a cathode gas humidification unit 5 for humidifying the cathode gas is installed between the stack 1 and the cathode gas supply unit 3.

  First, the stack 1 shown in FIG. 1 will be described.

FIG. 2 shows a side view of the stack 1. In FIG. 2, the stack 1 has a single cell 43 in which a plurality of layers are stacked. The unit cell 43 is the same as that described in the background art. The unit cell 43 includes a MEA 42 having a pair of gas diffusion layers and an electrolyte membrane, a gasket, a separator formed on the surface in contact with the MEA 42 in order to supply fuel gas to the MEA 42, and an oxidizing gas in the MEA 42. The cathode gas flow path has a separator formed on the surface in contact with the MEA 42.
Note that the anode and the cathode constituting the MEA 42 both indicate gas diffusion electrodes having gas diffusibility. More specifically, both the anode and the cathode may be composed of a catalyst layer having gas diffusibility, or may be a laminate in which the above catalyst layer is formed on the gas diffusion layer. Further, the anode and the cathode have a configuration in which one or more other layers (for example, a layer made of a porous material having gas diffusibility, electron conductivity, and water repellency) are disposed between the gas diffusion layer and the catalyst layer. It may be.

    In this Embodiment 1, two types of separators which are examples of the separator of the present invention are used as this separator, and one is a separator 40 having a fuel gas passage 13 and a cooling water passage 18. The other is a separator 41 having an oxidizing gas channel 19 and a cooling water channel 18.

  These two types of separators are arranged so that the fuel gas passage 13 forming surface of the separator 40 and the oxidant gas passage 19 forming surface of the separator 41 face each other with the MEA 42 interposed therebetween. By arranging in this way, the single cells 43 have the cooling portions 44 formed by the cooling water flow paths 18 at both ends thereof. Although not described, gaskets are provided between the MEA 42 and between the separators 40 and 41 and between adjacent unit cells 43.

  FIG. 3A is a plan view of the separator 40 shown in FIG. Moreover, FIG.3 (b) is a top view of the surface on the opposite side to Fig.3 (a) of the separator 40 shown in FIG. FIG. 3C is a side view of the separator 40 shown in FIG. Since the separator 41 shown in FIG. 2 has the same configuration as the separator 40, detailed description thereof is omitted.

  As shown in FIG. 3A, an anode gas inlet manifold 11, an anode gas outlet manifold 12, a cathode gas inlet manifold 14, and a cathode gas outlet manifold 15 are formed around the end when viewed from the plane 40a of the separator 40. ing. A cooling water inlet manifold 16 and a cooling water outlet manifold 17 are also formed. Each of the outlets and the inlet manifold is provided at a point-symmetrical position with respect to the center of the plane of the substantially square separator 40. Further, the anode gas inlet manifold 11 and the cathode gas inlet manifold 14 are provided adjacent to each other in the vicinity of one side of the flat surface 40 a of the separator 40. The anode gas outlet manifold 12 and the cathode gas outlet manifold 15 are provided adjacent to each other in the vicinity of the opposite side. The cooling water inlet manifold 16 and the cooling water outlet manifold 17 are provided on the remaining two sides. The cooling water inlet manifold 16 is provided near the anode gas inlet manifold 11.

  A plurality of parallel grooves constituting the fuel gas flow path 13 are formed in a zigzag manner from the anode gas inlet manifold 11 to the anode gas outlet manifold 12. A plurality of parallel cooling water channel grooves constituting the cooling water channel 18 are formed in a zigzag manner from the cooling water inlet manifold 16 to the cooling water outlet manifold 17 on the opposite surface where the fuel gas channel 13 is formed. ing.

    The stack 1 shown in FIG. 1 has been described above.

    Next, parts other than the stack 1 in FIG. 1 will be described.

    That is, between the anode gas inlet manifold 11 shown in FIGS. 3A and 3B and the anode gas humidifying unit 4 shown in FIG. 1, as shown in FIG. An anode buffer mechanism unit 20 which is an example of the buffer mechanism unit of the present invention for adding water is installed. As shown in FIG. 1, the anode buffer mechanism unit 20 is an anode buffer mechanism reserve which is an example of a reserve unit of the present invention directly connected to the anode gas inlet manifold 11 for storing moisture to be added to the fuel gas. A portion 29 is provided.

  As shown in FIG. 1, the cathode buffer mechanism section 30, which is an example of the buffer mechanism section of the present invention, is also provided between the cathode gas inlet manifold 14 on the cathode side and the cathode gas humidifying section 5, as in the anode side. As shown in FIG. 1, the cathode buffer mechanism unit 30 has a cathode buffer mechanism storage unit 39 which is an example of the storage unit of the present invention.

  The stack 1, the anode buffer mechanism storage unit 29, and the cathode buffer mechanism storage unit 39 have an integrated configuration and are covered with a heat insulating material 10 as shown in FIG. 1.

  In FIG. 1, in the above-described anode buffer mechanism storage unit 29, an anode buffer mechanism heat exchange unit 21 which is an example of the heating unit of the present invention for heating the stored water, and an anode buffer for detecting the level of the stored water A mechanism water level detection unit 22 is installed. Further, an anode buffer mechanism drain port 24 for discharging the water stored in the anode buffer mechanism storage unit 29 is provided. Further, in the anode buffer mechanism, an anode buffer mechanism humidity detector 23 for detecting the amount of water vapor in the buffer mechanism is installed.

  1, in the cathode buffer mechanism storage unit 39, as in the anode buffer mechanism storage unit 29, the cathode buffer mechanism heat exchange unit 31 which is an example of the heating unit of the present invention, and the cathode buffer mechanism water level detection unit 32, a drain port 34, and a cathode buffer mechanism humidity detector 33 are installed.

  In FIG. 1, an anode heating medium flow path 6 is formed from an anode buffer mechanism heating medium supply section 25 installed outside the heat insulating material 10 to an anode buffer mechanism heat exchange section 21, and this anode heating medium flow path 6 is provided with an anode buffer mechanism heating adjustment valve 26 for adjusting the flow rate of the heating medium. Further, the anode buffer mechanism drain port 24 communicates with the outside of the heat insulating material 10, and an anode buffer mechanism drain valve 27 for adjusting the discharge of the stored water is installed. Also, the opening / closing of the anode buffer mechanism drain valve 27 is controlled by the water level of the stored water detected by the anode buffer mechanism water level detection unit 22, and the anode buffer mechanism heating adjustment valve 26 is controlled by the humidity detected by the anode buffer mechanism humidity unit 23. An anode buffer mechanism control unit 28 for controlling the opening and closing of is installed.

  That is, the anode buffer mechanism unit 20 includes an anode buffer mechanism storage unit 29, an anode buffer mechanism heat exchange unit 21, an anode buffer mechanism water level detection unit 22, an anode buffer mechanism humidity detection unit 23, an anode buffer mechanism drain port 24, and an anode buffer mechanism. A heating medium supply unit 25, an anode heating medium flow path 6, an anode buffer mechanism heating adjustment valve 26, an anode buffer mechanism drain valve 27, and an anode buffer mechanism control unit 28 are provided.

  Similarly to the anode side, the cathode buffer mechanism heating medium supply section 35, the cathode heating medium flow path 8, the cathode buffer mechanism heating adjustment valve 36, the cathode buffer mechanism drain valve 37, and the cathode buffer mechanism control are also provided on the cathode side. Part 38 is installed.

      Here, the heating medium supplied from the anode buffer mechanism heating medium supply unit 25 to the anode buffer mechanism heat exchange unit 21 uses at least one of the following (1) to (4) as the stack cooling water from which the heat generated by the stack has been removed. Or the combustion exhaust gas from any one of the heat sources of (1) to (4), and the control of the exchange heat quantity is also from the anode buffer mechanism control unit 28. This is performed by controlling the combustion amount of a reformer or a dedicated burner not shown here. Also, the time constant for the system operation behavior (start / stop, load fluctuation) and its control constant are preset in the control storage medium not shown here corresponding to each operation mode, and controlled by the learning control program during actual operation Set by fine-tuning the constant. The same applies to the cathode side.

(1) Waste heat of the reformer (2) Heat of the hydrogen-rich fuel gas supplied from the reformer to the stack (3) Heat obtained by burning fuel (4) From the stack Heat obtained by burning the residual fuel gas discharged Note that the above 1 (1) to (4) will be described in detail in a third embodiment to be described later.

  The configuration of the anode buffer mechanism 20 and the cathode buffer mechanism 30 shown in FIG. 1 will be specifically described below.

  4 is a configuration perspective view of the stack 1, the anode buffer mechanism unit 20, and the cathode buffer mechanism unit 30 shown in FIG. The anode buffer mechanism reserve unit 29 and the cathode buffer mechanism reserve unit 39 in FIG. 1 are formed by stacking a plurality of buffer mechanism unit separators 50 and 60, as shown in FIG. The plurality of buffer mechanism separators 50 and 60 are stacked on the stack 1, and an end plate 51 is disposed on the opposite side of the stack 1.

  Next, the buffer mechanism section separator 50 will be described in detail.

  FIG. 5A shows a groove forming surface for the buffer mechanism reserve part of the buffer mechanism part separator 50. FIG. 5B shows a heating medium channel groove forming surface of the buffer mechanism separator 50. FIG. 5C is a cross-sectional view taken along the line AA ′ of FIG.

  As shown in FIG. 5A, on one surface 50a of the buffer mechanism separator 50, two anode gas outlet manifolds 52 and a cathode gas outlet manifold 53 are formed side by side in the vicinity of the upper side when viewed from the stacking direction. . Also, an anode gas inlet manifold 54 and a cathode gas inlet manifold 55 are formed side by side in the lower part of each gas outlet manifold and in the vicinity of the lower side of the buffer mechanism separator 50.

  Further, a heating medium inlet manifold 58 and a heating medium outlet manifold 59 are provided in the vicinity of two sides (left and right sides in FIG. 5A) other than where the gas outlet manifolds 52 and 53 and the gas inlet manifolds 54 and 55 are formed. Each is formed on one side. The heating medium inlet manifold 58 and the heating medium outlet manifold 59 are formed at positions that are substantially point symmetric with respect to the center of the substantially square buffer mechanism section separator 50. Further, the coolant inlet manifold 16 and the coolant outlet manifold 17 formed in the separator 40 are also formed in the buffer mechanism separator 50.

  An anode storage water discharge manifold 70 is installed between the cooling water inlet manifold 16 and the heating medium outlet manifold 59 and in the vicinity of the side of the buffer mechanism separator 50. Further, a cathode reserve water discharge manifold 80 is installed between the cooling water outlet manifold 17 and the heating medium inlet manifold 58 and in the vicinity of the side of the buffer mechanism separator 50.

  Also, an anode buffer mechanism storage groove 56 is provided between the anode gas outlet manifold 52 and the anode gas inlet manifold 54, and a cathode buffer mechanism storage groove 57 is provided between the cathode gas outlet manifold 53 and the cathode gas inlet manifold 55. It is formed on the surface 50 a of the buffer mechanism section separator 50.

  The anode buffer mechanism reserve portion groove 56 has a water reserve portion groove 56a whose bottom is closed. Further, the anode buffer mechanism reserve portion groove 56 is formed from the anode gas outlet manifold 52 toward the upper portion of the water reserve portion groove 56a and from above the upper portion of the water reserve portion groove 56a. It has a gas inlet groove 56 c that is folded back in the direction and formed into the lower anode gas inlet manifold 54. Further, a water discharge groove 56d is formed from the water storage portion groove 56a to the anode storage water discharge manifold 70. A cathode buffer mechanism reserve groove 57 having the same shape as the anode buffer mechanism reserve groove 56 is also formed between the cathode gas outlet manifold 53 and the cathode gas inlet manifold 55.

  A heating medium flow channel groove 46 is formed on the surface 50b opposite to the surface on which the buffer mechanism storage groove 56 is formed. The heating medium passage groove 46 is formed in a zigzag shape from the heating medium inlet manifold 58 to the heating medium outlet manifold 59.

  The buffer mechanism separator 60 is formed with outlet manifolds, anode and cathode buffer mechanism reserve grooves 56 and 57, and a heating medium channel groove 46 so as to be symmetrical with the buffer mechanism separator 50. Has been. Other than that, the buffer mechanism section separator 60 has the same configuration as the buffer mechanism section separator 50, and thus detailed description of the buffer mechanism section separator 60 is omitted.

  When the buffer mechanism separators 50 and 60 are stacked as shown in FIG. 4, the positions of the manifolds of the buffer mechanism separators 50 and 60 and the separators 40 and 41 shown in FIG. 2 correspond as shown below. .

  That is, the anode gas outlet manifold 52 of the buffer mechanism section separators 50 and 60 shown in FIGS. 5 (a), 5 (b), and 5 (c), and FIGS. 3 (a) and 3 (b). The positions of the separator 40 and the anode gas inlet manifold 11 of the separator 41 coincide with each other when stacked.

    Further, the cathode gas outlet manifold 53 of the buffer mechanism separators 50 and 60 shown in FIGS. 5A, 5B, and 5C, and FIGS. 3A and 3B are shown. Further, the positions of the cathode gas inlet manifolds 14 of the separators 40 and 41 coincide with each other when stacked.

    Further, the anode gas inlet manifold 54 of the buffer mechanism separators 50 and 60 shown in FIGS. 5A, 5B, and 5C, and FIGS. 3A and 3B are shown. The positions of the cathode gas outlet manifold 15 of the separators 40 and 41 coincide with each other at the time of stacking.

    Further, the cathode gas inlet manifold 55 of the buffer mechanism section separators 50 and 60 shown in FIGS. 5A, 5B, and 5C and those shown in FIGS. 3A and 3B. The positions of the anode gas outlet manifold 12 of the separators 40 and 41 coincide with each other at the time of stacking.

  6 is a side sectional view of the buffer mechanism shown in FIG. 1 and the stack 1 shown in FIG. That is, here, the anode side will be described as an example. As shown in FIG. 6, the buffer mechanism separators 50 and 60 shown in FIGS. 5 (a), 5 (b), and 5 (c) are surfaces on which the respective buffer mechanism reserve grooves 56 are formed. Are combined to form the buffer mechanism reserve component 29a. A plurality of buffer mechanism reserve components 29a are formed by alternately stacking the buffer mechanism separators 50 and 60, and the buffer mechanism reserve 29 described in the conceptual diagram of FIG. 1 is configured.

  Further, the heating medium flow path 47 is formed between the buffer mechanism reserve components 29a by combining the formation surfaces of the heating medium flow path grooves 46 of the separator 50 and the separator 60 (see FIG. 5B). Is done. The plurality of heating medium flow paths 47 constitute a heat exchanging section 48 which is an example of the heating section of the present invention. In the conceptual diagram of FIG. 1, the anode heating medium flow path 6 and the cathode heating medium flow path 8 provided separately are shown in FIG. 6, which is a specific example, in the anode buffer mechanism reserve section 29 shown in FIG. This corresponds to the heating medium flow path 47 that heats both the cathode buffer mechanism storage part 39 and the cathode buffer mechanism storage part 39. Further, the anode buffer mechanism heat exchanging portion 21 and the cathode buffer mechanism heat exchanging portion 31 in FIG. 1 also correspond to the heat exchanging portion 48 in FIG.

  Further, as shown in FIG. 6, the buffer mechanism section separator in contact with the stack 1 is a buffer mechanism section end separator 61 in which the anode gas inlet manifold 54 is not formed. In addition, the cooling water inlet / outlet manifolds 16 and 17 of the separators 40 and 41 shown in FIGS. 3A and 3B are provided in the buffer mechanism separators 50, 60, and 61, but the flow paths are formed. Therefore, the buffer mechanism part separators 50, 60, 61 are fed to the stack 1. Also, the heating medium inlet and outlet manifolds 58 and 59 of the buffer mechanism separators 50 and 60 shown in FIGS. 5A and 5B are shown in FIGS. 3A and 3B of the stack 1. The separators 40 and 41 shown are not provided. However, it may be provided when it is desired to pass the heating medium through the stack 1 in the layout.

  In FIG. 6, an end plate 51 is provided on the opposite side of the stack 1 of the stacked buffer mechanism separators 50 and 60.

  As shown in FIG. 4, the end plate 51 has an optically low level sensor via a viewing window 62 at positions corresponding to the anode buffer mechanism reserve unit 29 and the cathode buffer mechanism reserve unit 39 shown in FIG. 63 (corresponding to the anode buffer mechanism water level detection unit 22 shown in FIG. 1) is provided for detecting the level of the stored water. Further, the anode buffer mechanism drain port 24 and the anode buffer mechanism drain valve 27 described in FIG. 1 for discharging the water stored in the anode buffer mechanism storage unit 29 shown in FIG. As shown in FIG. 4, the end plate 51 and the buffer mechanism separators 50 and 60 are installed. In FIG. 4, an anode gas humidity sensor 220 and a cathode gas humidity sensor 221 are embedded in the end plate 51 at positions corresponding to the anode gas outlet manifold 52 and the cathode gas outlet manifold 53 of the buffer mechanism when stacked. It is electrically connected to a control unit (not shown).

  Although not shown, a level sensor 63, a cathode buffer mechanism drain port 34, and a cathode buffer mechanism drain valve 27 are also provided on the cathode side.

  In the conceptual diagram of FIG. 1, the anode buffer mechanism water level detection unit 22 that detects the water level corresponds to the level sensor 63 via the viewing window 62 in the end plate 51 in the specific example of FIG. 4, but is not limited thereto. Not what you want. In short, the anode buffer mechanism water level detection unit 22 only needs to be able to detect the water level stored in the buffer mechanism storage unit. Further, it can be omitted in the auto drain mode as shown in FIG.

  4, the end plate 51 has an anode gas supply pipe 64 and a cathode gas supply pipe 65 at positions corresponding to the anode gas inlet manifold 54 and the cathode gas inlet manifold 55 of the buffer mechanism separators 50 and 60. Yes. Similarly, the end plate 51 includes a cooling water supply pipe 66, a cooling water discharge pipe 67, a heating medium supply pipe 68, and a heating medium discharge pipe 69 at positions corresponding to the inlet / outlet manifolds of the buffer mechanism separators 50 and 60. is set up.

  The operation of the fuel cell system according to Embodiment 1 configured as described above will be described below. The description will be given by taking the anode gas side as an example, but the same applies to the cathode gas side.

  The dew point given to the fuel gas in the anode gas humidifying unit 4 is T1. The temperature in the anode buffer mechanism storage unit 29 is maintained at T2 by adjusting the flow rate of the heating medium by the anode buffer mechanism control unit 28 adjusting the anode buffer mechanism heating adjustment valve 26.

The temperature at the inlet of the fuel gas passage 13 of the MEA 42 is T3.
The fuel gas generated from the anode gas supply unit 2 and given the dew point of T1 by the anode gas humidification unit 4 passes through the anode gas supply pipe 64 of the end plate 51 as shown by the arrow in FIG. Into the anode gas inlet manifold 54 of the partial separators 50, 60.

  Next, a plurality of buffer mechanism reserve components shown in FIG. 6 are provided through the gas inlet groove 56c of the buffer mechanism reserve groove 56 shown in FIG. 5A provided in each buffer mechanism separator 50, 60. It flows into 29a. Since the buffer mechanism section separator 61 in contact with the stack 1 is not provided with the anode gas inlet manifold 54, all the fuel gas flows into the buffer mechanism reserve component 29a. Here, of the water vapor contained in the fuel gas, the water vapor corresponding to the dew point at the internal temperature (T2) of the anode buffer mechanism reserve component 29a is not liquefied in the anode buffer mechanism reserve component 29a. The anode gas outlet manifold 52 shown in FIGS. 5 (a) and 5 (b) supplies the anode gas inlet manifold 11 of the stack 1 shown in FIG.

  Next, it is cooled to T3 at the inlet of the fuel gas passage 13 of the MEA 42. Here, if there is stockpile water in the anode buffer mechanism stockpile 29 and the relationship of T2> T3 is always established, water vapor is saturated with respect to T3 at the gas inflow part of the MEA 42. In order to make water vapor supersaturated with respect to T3, for example, the anode buffer mechanism control unit 28 performs control to adjust the amount of heat supplied from the heat medium so that T2 becomes a certain value higher than T3. At this time, flooding can be avoided if the anode buffer mechanism control unit 28 controls the relationship between T3 and T2 so that T3 + 10> T2 and T2 becomes a certain value higher than T3.

  Further, in this system, if the relationship of T1> T2 is always established, the reserve water is increased while the excess reserve water is supplied from the anode buffer mechanism reserve unit 29 to the anode reserve water discharge manifold 70 shown in FIG. It can be discharged through the anode buffer mechanism drain port 24 and supplied to other auxiliary machines. For example, it is returned to the humidifying units 4 and 5 for reuse, or used as operating water for the reformer.

  In addition, when T1 <T2 is temporarily satisfied in the operation of the system in this system, the shortage will be supplied from the stored water by natural evaporation, and the supply of water vapor to the battery will not be insufficient. From the point of time when the system operation is stabilized and T1> T2, the stored water starts to increase again.

  In the above example, the temperature of the total heat exchanger (not shown) is maintained at 78 ° C. by using an auxiliary heat source to maintain the dew point (T1) of the supply gas at 74 ° C., and this is maintained at 72 ° C. (T2). It is introduced into the maintained anode buffer mechanism reserve 29 and supplied to the gas inlet of the MEA 42 at a battery temperature of 70 ° C. (T3 = about 71 ° C.). Table 1 shows the saturated water vapor amount of water at each temperature.

    In this way, the amount of water vapor supplied from the water vapor supply system is basically controlled to be excessive with respect to the amount required for battery operation. , Stock the part of MEA that is not immediately effective in preventing drying. The stocked water is re-vaporized with a heat source at or above the battery temperature to give a water vapor volume above the saturated water vapor volume at the battery temperature. Thereafter, control is performed to cool and saturate at the temperature of the gas inflow portion of the MEA 42 in the stack manifold (oversaturation with respect to the battery temperature that can be detected in this portion), that is, adjustment control (buffering). I do.

  As described above, by supplying a gas containing water vapor that is higher than the saturated water vapor amount at the temperature of the gas inflow portion of the MEA, the supply gas can maintain the saturated water vapor amount more reliably in all parts of the MEA.

  In addition, by providing a buffer mechanism, there is a control factor such as a temporary decrease in the supply capacity of the gas humidifiers 4 and 5 with respect to the required amount of the battery, and there is an increase in power load. In the situation where the steam supply capacity of the gas humidifier does not catch up with the amount of water vapor in terms of response speed (time lag), the water stored inside can be vaporized to compensate for this deficiency, and buffering or adjustment can be performed .

  Further, by providing a buffer mechanism stocking part directly connected to the gas inlet manifold and performing thermal insulation at a time, it is possible to prevent a decrease in gas temperature. That is, the reaction gas condensed in the pipes from the gas humidifying units 4 and 5 to the stack 1 and having a substantial reduced water vapor amount is returned to the dew point above the battery temperature again, and is consumed by the battery without condensation again. The layout can be taken.

  For this reason, it is possible to provide a fuel cell system or a method for operating the fuel cell system that can perform stable operation with a longer life even in applications (particularly, stationary cogeneration systems) that are rated at low current density.

(Embodiment 2)
FIG. 7 is a conceptual diagram of the fuel cell system according to the second embodiment. As shown in FIG. 7, the fuel cell system according to the second embodiment has the same basic configuration as that of the first embodiment, but the anode buffer mechanism and the cathode buffer mechanism are provided in the anode and cathode gas inlet manifolds. Different points. Therefore, the difference between the second embodiment and the first embodiment will be mainly described. In addition, the same number is attached | subjected to the component same as Embodiment 1. FIG.

  FIG. 8A is a configuration perspective view of the stack 1 (FIG. 7) of the fuel cell system according to the second embodiment. As shown in FIG. 8A, the fuel cell system according to the second embodiment includes anode and cathode gas inlet manifolds 71 and 81 having a shape different from that of the anode and cathode gas inlet manifolds 11 and 14 according to the first embodiment. ing. Further, unlike the first embodiment, the end plate 90 is directly stacked on the stack 1 without providing the buffer mechanism section separator.

  FIG. 8B is an enlarged perspective view of the cathode gas inlet manifold 81. FIG. 8C is an enlarged plan view of the cathode gas inlet manifold 81 as viewed from the end plate 90 in the stack 1 direction. As shown in FIG. 8C, the right side 81a at the bottom of the cathode gas inlet manifold 81 protrudes into the cathode gas inlet manifold 81, and the left side 81b is an example of a storage unit according to the present invention that can store water. The cathode buffer mechanism reserve part 82 is. A cathode buffer mechanism heat exchanging unit 83 which is an example of the heating unit of the present invention having the cathode buffer mechanism heating medium flow path 84 is installed at the bottom of the cathode buffer mechanism storage unit 82. An oxidant gas flow channel groove 86, which is a groove for the oxidant gas flow channel 19, is formed from the right side 81 a of the cathode gas inlet manifold 81. Further, the cathode gas inlet manifold 81 provided in the end plate 51 does not penetrate the end plate 90, and the end plate 90 is disposed above the cathode gas inlet manifold 81 as shown in FIG. A cathode gas supply pipe 91 is provided. 8A, the end plate 90 has an anode gas humidity sensor 220 and a cathode gas humidity sensor 221 for detecting the humidity in the anode gas inlet manifold 71 and the cathode gas inlet manifold 81, respectively. ing.

  As described above, the cathode buffer mechanism 30 in the first embodiment includes the cathode buffer mechanism storage unit 82 and the cathode buffer mechanism heat exchange unit 83 provided in the cathode gas inlet manifold 81 in the second embodiment. This corresponds to the cathode buffer mechanism 85 having the same.

  Similarly to the cathode side, the anode gas inlet manifold 71 is provided with an anode buffer mechanism reserve portion 72 which is an example of a reserve portion of the present invention on the right side of the bottom, and a groove of the fuel gas flow path 13 is formed from the left side of the bottom portion. Yes. Similarly to the cathode side described above, an anode buffer mechanism heat exchange unit 73 which is an example of the heating unit of the present invention having the anode buffer mechanism heating medium flow path 74 is installed at the bottom of the anode buffer mechanism storage unit 72.

  As described above, the anode buffer mechanism unit 20 in the first embodiment includes the anode buffer mechanism storage unit 72 and the anode buffer mechanism heat exchange unit 73 provided in the anode gas inlet manifold 71 in the second embodiment. This corresponds to the anode buffer mechanism portion 75 having the above-described structure. The end plate 90 is provided with an anode gas supply pipe 92 joined to the upper part of the anode gas inlet manifold 71.

  Further, the end plate 90 has an anode viewing window 93 and a cathode viewing window 94 for detecting the water level stored in the anode and cathode buffer mechanism reserves 72 and 82 as in the first embodiment. Although not shown, optical level sensors are respectively installed in the viewing windows 93 and 94. Further, the end plate 90 has a cooling water supply pipe 95 at a position corresponding to the cooling water inlet manifold 16 of the stack 1 and a cooling water discharge pipe 96 at a position corresponding to the cooling water outlet manifold 17.

  The anode gas inlet manifold 71, the cathode gas inlet manifold 81, and the cooling water inlet manifold 16 are all located in the upper part of the stack 1, but in this stack, the temperature is increased toward the upper part by flowing all the fluid vertically downward. It is designed to be low (because each fluid is heated by the heat generated by the stack 1 as it flows downward, the temperature at the bottom is higher than the top).

  In the fuel cell system according to the second embodiment, the cooling water discharge pipe 96 is provided with a branch valve 97, and the cooling water branched by the branch valve 97 is supplied to the anode buffer mechanism heating medium channel 74 and the cathode. The buffer mechanism is configured to flow into the heating medium flow path 84.

  An external heat exchanger 98 is installed between the branch valve 97 and the anode buffer mechanism heating medium flow paths 74 and 84 to replenish heat drawn from a heat source other than the stack 1 when the cooling water temperature is insufficient. Yes.

  In the conceptual diagram of FIG. 7, the anode buffer mechanism water level detection unit 22 that detects the water level corresponds to a level sensor in the specific example of FIG. 8 via the viewing windows 93 and 94 in the end plate 90. It is not limited. In short, the anode buffer mechanism water level detection unit 22 only needs to be able to detect the water level stored in the buffer mechanism storage unit.

  In addition, the heating medium supply unit that supplies the heating medium to the heating medium flow paths 74 and 84 is illustrated separately from the anode buffer mechanism heating medium supply unit 25 and the cathode buffer mechanism heating medium supply unit 35 in FIG. In FIG. 8A, since there is one flow path for supplying the heating medium to the heating medium supply units 84 and 94, it is not necessary to separately install the heating medium supply unit.

  The operation of the fuel cell system according to the second embodiment having the above configuration will be described below. The cathode side will be described, but the same applies to the anode side.

  The oxidant gas supplied from the cathode gas supply unit 3 and humidified by the cathode gas humidification unit 5 flows into the cathode gas inlet manifold 81 from the cathode gas supply pipe 91.

Next, a portion lower than the dew point in the cathode gas inlet manifold 81 flows into the oxidant gas flow channel groove 86.
The amount of water vapor in the cathode gas inlet manifold 81 is constantly monitored by the cathode gas humidity sensor 221, and the amount of water vapor is always higher than the saturated water vapor amount at T3 (temperature of the oxidant gas flow path inlet of the MEA 42). When the heat is supplied to the buffer mechanism heat exchanging unit 83 and the stored water is vaporized, the dew point is always higher than the temperature of the unit cell 43 at the time of branching to the unit cell 43 from here.

  Compared with the first embodiment, the second embodiment is advantageous in that the distribution of water vapor is evenly performed by each cell even when the number of stacked layers is increased to obtain a high voltage and the stack length is increased. It has many points.

  Further, the second embodiment is superior to the first embodiment in that water vapor is more evenly distributed to each unit cell. That is, in the form shown in the first embodiment, the distances from the buffer mechanism units 20 and 30 to the individual cells 43 (the actual pipe length) are unequal, especially due to condensation in the manifold during multi-stage stacking. The amount of water vapor is insufficient in the part far from the buffer mechanism. In the second embodiment, since the water is stored in the gas manifold, the pipe length is uniform and the shortest.

  Further, in the first embodiment, there is a packaging problem that when the number of stacked layers of the stack 1 increases, the number of stacked layers of the buffer mechanism section separators 50 and 60 must be increased accordingly. Then, since a certain area of the gas manifold is used as a storage space, the amount of stored water is automatically proportional to the number of stacked layers, so this problem does not occur.

  Further, the control unit of the present invention corresponds to the anode buffer mechanism control unit 28 and the cathode buffer mechanism control unit 38 in the first and second embodiments, and controls the revaporization amount of water stored in the storage unit. . As for the means for controlling the re-vaporization amount, feedback control may be performed using a humidity sensor as described above, or the same control may be performed by detecting the absolute amount of vaporized water at the water level. In short, the heating part is controlled so that the temperature of the water provided in the storage part is kept higher than the temperature of the electrolyte membrane at the inlet of the gas flow channel groove, and the water is re-vaporized and stacked. What is necessary is just a control part to supply to the single cell.

  Further, the buffer mechanism unit of the present invention corresponds to the anode buffer mechanism unit 20 and the cathode buffer mechanism unit 30 in the first embodiment, and the anode buffer mechanism unit 75 and the cathode buffer mechanism unit 85 in the second embodiment. Although it is provided on both sides of the anode side and the cathode side, only one of them may be installed. In this case, compared with the conventional fuel cell system, stable operation can be performed with a longer life. However, in order to prevent the MEA from drying, it is more preferable to provide buffer mechanisms on both the anode and cathode sides. preferable.

  Further, the configuration of the buffer mechanism described in the first and second embodiments is not limited. In any case, this buffer mechanism adjusts the water vapor amount of the reaction gas supplied to a plurality of single cells, and even has a function (buffering) that constantly supplies a water vapor amount equal to or higher than the saturated water vapor amount at the battery temperature. do it. Further, as described above, the heating medium may be used after the battery cooling wastewater is once subjected to heat exchange with a heat source other than the battery, and the combustion exhaust gas from the heat source other than the battery is directly used as the anode buffer mechanism heating medium channel 74 and the cathode. The stored water may be heated directly in the manifold by drawing into the buffer mechanism heating medium flow path 84.

(Embodiment 3)
In the third embodiment, a heat supply unit that supplies heat to the buffer mechanism storage unit, which is used in common with the first and second embodiments, will be described.

As a heat supply means to the buffer mechanism storage unit that is commonly used in both the first and second embodiments, a fluid having a temperature higher than T3 (temperature at the gas inlet of the MEA) is buffered through the heating medium flow path. A method of introducing heat into the mechanism and exchanging heat with the stored water in the buffer mechanism is simple and reliable. In an actual fuel cell system, there are the following options as heat sources other than battery exhaust heat.
(1) Waste heat of the fuel reformer that the anode gas supply unit 2 has.
(2) A method of introducing humidified hydrogen gas (temperature of about 150 degrees) supplied from the fuel reformer.
(3) A method of burning the fuel itself for this purpose.
(4) Method of combusting off-gas (excess hydrogen gas remaining at the anode) for this purpose The above options will be described below. The description will be made by taking the first embodiment as an example, but the same applies to the second embodiment.

  (1) is a method of heating the heating medium using this waste heat as a heat source because it is necessary to heat the anode gas supply unit 2 when reforming from fuel gas to hydrogen-rich gas. . FIG. 9 is a schematic diagram of the fuel cell system according to the third embodiment (1). In addition, the same number is attached | subjected about the structure same as Embodiment 1 shown in FIG.

  As shown in FIG. 9, the anode heating medium flow path 6 and the cathode heating medium flow path 8 constitute a flow path to the reformer of the anode gas supply unit 2. In addition, the anode heating medium flow path 6 and the cathode heating medium flow path 8 merge before the reformer, and the heating medium is heated by the waste heat of the reformer. The heated heating medium branches into the anode heating medium flow path 6 and the cathode heating medium flow path 8 and is supplied to the anode buffer mechanism reserve section 29 and the cathode buffer mechanism reserve section 39.

  (2) is a method in which the heat of the humidified hydrogen gas supplied from the fuel reformer of the anode gas supply unit 2 to the stack 1 is used as a heat source and introduced into the anode heating medium channel 6 and the cathode heating medium channel 8. It is. FIG. 10 is a schematic diagram of the fuel cell system in (2) of the third embodiment. As shown in FIG. 10, a heat exchanger 138 is installed in the humidified fuel gas passage. An anode heating medium channel 6 and a cathode heating medium channel 8 are installed in the heat exchanger 138. The anode heating medium flow path 6 and the cathode heating medium flow path 8 merge before the heat exchanger 138, and the heating medium is heated by heat transfer from the humidified fuel gas in the heat exchanger 138. . The heated heating medium branches into the anode heating medium flow path 6 and the cathode heating medium flow path 8 and is supplied to the anode buffer mechanism reserve section 29 and the cathode buffer mechanism reserve section 39.

  (3) is a method of burning another fuel in order to heat the heating medium introduced into the heating medium flow path. FIG. 11 is a schematic diagram of the fuel cell system according to (3) of the third embodiment. As shown in FIG. 11, the difference from the above (2) of the fuel cell system (3) is that the heat exchanger 138 is not installed and the heating medium is heated by burning other fuel. The heating unit 139 is installed. The heating medium heated by the heating unit 139 is supplied to the anode buffer mechanism reserve unit 29 and the cathode buffer mechanism reserve unit 39 as in (2) above.

  (4) is a method of burning surplus fuel gas on the anode side in order to heat the heating medium introduced into the heating medium flow path. FIG. 12 is a schematic diagram of the fuel cell system according to (4) of the third embodiment. As shown in FIG. 12, the fuel cell system of (4) differs from the above (3) in that the heating unit 139 is not installed, and the fuel gas combustion that heats the heating medium by burning surplus fuel gas The heating unit 140 is installed. In this fuel cell system, a flow path for supplying unused surplus fuel gas to the fuel gas combustion heating unit 140 in the stack 1 is installed, and surplus fuel gas is burned by the fuel gas combustion heating unit 140. As a result, the heating medium is heated.

  In order to perform the above (3) and (4), a dedicated burner for burning these raw fuel or off gas may be provided, or this role is imposed on the reformer burner driven by raw fuel or off gas. It is also possible to make it. That is, for example, the reformer combustion exhaust gas is constantly introduced into the buffer mechanism, and when the dew point is insufficient, in addition to the combustion amount necessary for the normal reforming reaction, the combustion amount necessary for additional humidification is given to the reformer burner. This purpose can be achieved by performing such control.

  The heat from these heat sources is exchanged with the cooling water discharged from the stack 1 at one end and introduced into the buffer mechanism, or directly introduced into the buffer mechanism. Hereinafter, a specific example in which heat from the heat source is once exchanged with cooling water discharged from the stack 1 and introduced into the buffer mechanism, and heat from the heat source is directly introduced into the buffer mechanism. A specific example will be described.

  FIG. 13 is a schematic diagram of the fuel cell system of the third embodiment. Of the fuel cell system of the first embodiment, the anode buffer mechanism heating medium supply unit 25 and the cathode buffer mechanism heating medium supply unit 35 of FIG. It is the figure which showed the part in detail. FIG. 13 is a specific example in the case where the heat from the heat source is directly introduced into the buffer mechanism. In FIG. 13, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In FIG. 13, a heat medium carrying heat from the heat sources (1) to (4) is introduced into the anode buffer mechanism heating medium supply unit 25 via the heat medium introduction pipe 205. Then, the anode buffer mechanism heating medium supply unit 25 supplies the introduced heat medium directly to the anode buffer mechanism heat exchange unit 21 via the anode heating medium flow path 6. Then, the heat medium exchanged with the anode reserve water in the anode buffer mechanism heat exchange unit 21 returns to the anode buffer mechanism heating medium supply unit 25 via the anode heating medium flow path 6, and the anode buffer mechanism heating medium supply unit 25 is discharged via a heat medium discharge pipe 206.

  Similarly, in FIG. 13, a heat medium carrying heat from the heat sources (1) to (4) is introduced into the cathode buffer mechanism heating medium supply unit 35 via the heat medium introduction pipe 210. The cathode buffer mechanism heating medium supply unit 35 supplies the introduced heat medium directly to the cathode buffer mechanism heat exchange unit 31 via the cathode heating medium flow path 8. Then, the heat medium exchanged with the cathode reserve water in the cathode buffer mechanism heat exchanging section 31 returns to the cathode buffer mechanism heating medium supply section 35 via the cathode heating medium flow path 8, and the cathode buffer mechanism heating medium supply section. 35 is discharged via a heat medium discharge pipe 211.

  As described above, in the fuel cell system of FIG. 13, the heat medium carrying the heat from the heat sources (1) to (4) directly enters the cathode buffer mechanism heat exchange unit 31 and the anode buffer mechanism heat exchange unit 21. This is done by conducting.

  FIG. 14 is a schematic diagram of the fuel cell system of the third embodiment. Of the fuel cell system of the first embodiment, the anode buffer mechanism heating medium supply unit 25 and the cathode buffer mechanism heating medium supply unit 35 of FIG. It is the figure which showed the part in detail. FIG. 14 is a specific example in the case where the heat from the heat source is once heat-exchanged with the cooling water discharged from the stack 1 and introduced into the buffer mechanism. 14, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In FIG. 14, the cooling water from the stack 1 is introduced into the anode buffer mechanism heating medium supply unit 25 via the cooling water introduction pipe 201, and the heat medium carrying the heat from the heat source is introduced into the anode medium. It is introduced via the pipe 205. Then, in the heat exchanger 204 of the anode buffer mechanism heating medium supply unit 25, heat exchange between the introduced cooling water from the stack 1 and the introduced heat medium is performed, and the cooling water from the stack 1 is heated. The The anode buffer mechanism heating medium supply unit 25 supplies the cooling water heated in the heat exchanger 204 to the anode buffer mechanism heat exchange unit 21 via the anode heating medium flow path 6. The cooling water of the stack 1 that has exchanged heat with the anode buffer reserve water in the anode buffer mechanism heat exchange unit 21 returns to the anode buffer mechanism heating medium supply unit 25 via the anode heating medium flow path 6, and further heats the anode buffer mechanism. It is discharged from the medium supply unit 25 via the cooling water discharge pipe 206. On the other hand, the heat medium subjected to heat exchange in the heat exchanger 204 is discharged from the heat medium discharge pipe 202 via the heat medium amount adjustment valve 203.

  Similarly, in FIG. 14, the cooling water from the stack 1 is introduced into the cathode buffer mechanism heating medium supply unit 35 via the cooling water introduction pipe 207, and the heat medium carrying the heat from the heat source is received. It is introduced via the heat medium introduction pipe 211. Then, in the heat exchanger 210 of the cathode buffer mechanism heating medium supply unit 35, heat exchange between the introduced cooling water from the stack 1 and the introduced heat medium is performed, and the cooling water from the stack 1 is heated. The The cathode buffer mechanism heating medium supply unit 35 supplies the cooling water heated in the heat exchanger 204 to the cathode buffer mechanism heat exchange unit 31 via the cathode heating medium flow path 8. The cooling water of the stack 1 that has exchanged heat with the cathode buffer storage water in the cathode buffer mechanism heat exchanging section 31 returns to the cathode buffer mechanism heating medium supply section 35 via the cathode heating medium flow path 8 and further heats the cathode buffer mechanism. It is discharged from the medium supply unit 35 via the cooling water discharge pipe 212. On the other hand, the heat medium subjected to heat exchange in the heat exchanger 210 is discharged from the heat medium discharge pipe 208 via the heat medium amount adjustment valve 209.

  As described above, in the fuel cell system of FIG. 14, the supply of heat from the heat sources (1) to (4) to the anode buffer mechanism heat exchange unit 21 and the cathode buffer mechanism heat exchange unit 31 carries the heat. This is performed by indirect conduction performed after heat exchange between the heat medium and the cooling water of the stack 1.

  FIG. 15 is a schematic diagram of the fuel cell system of the third embodiment, corresponding to the fuel cell system of the second embodiment, and the anode buffer mechanism heating medium supply unit 25 and the cathode buffer mechanism heating medium supply of FIG. It is the figure which showed the part of the part 35 in detail. FIG. 15 is a specific example in the case where the heat from the heat source is directly introduced into the buffer mechanism. 15, the same parts as those in FIG. 7 are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 16 is a perspective view of the configuration of the stack 1 of the fuel cell system of FIG. The fuel cell system of Embodiment 2 is provided with an external heat exchanger 98 and a branch valve 97 as shown in FIG. As shown in FIG. 16, the fuel cell system of FIG. 15 is provided with a heat medium introduction pipe 205 and a heat medium introduction pipe 210 in place of the external heat exchanger 98, the branch valve 97, and the like. In other respects, FIG. 16 is the same as FIG.

  In FIG. 15, a heat medium carrying heat from the heat sources (1) to (4) is introduced into the anode buffer mechanism heating medium supply unit 25 via the heat medium introduction pipe 205. Then, the anode buffer mechanism heating medium supply unit 25 supplies the introduced heat medium directly to the anode buffer mechanism heat exchange unit 21 via the anode heating medium flow path 6. Then, the heat medium exchanged with the anode reserve water in the anode buffer mechanism heat exchange unit 21 returns to the anode buffer mechanism heating medium supply unit 25 via the anode heating medium flow path 6, and the anode buffer mechanism heating medium supply unit 25 is discharged via a heat medium discharge pipe 206.

  Similarly, in FIG. 15, a heat medium carrying heat from the heat sources (1) to (4) is introduced into the cathode buffer mechanism heating medium supply unit 35 via the heat medium introduction pipe 210. The cathode buffer mechanism heating medium supply unit 35 supplies the introduced heat medium directly to the cathode buffer mechanism heat exchange unit via the cathode heating medium flow path 8. Then, the heat medium that has exchanged heat with the cathode reserve water in the cathode buffer mechanism heat exchange section returns to the cathode buffer mechanism heating medium supply section 35 via the cathode heating medium flow path 8, and the cathode buffer mechanism heating medium supply section 35. Is discharged via a heat medium discharge pipe 211.

  As described above, in the fuel cell system of FIG. 15, the heat medium carrying the heat from the heat sources (1) to (4) is directly conducted to the cathode buffer mechanism heat exchange unit and the anode buffer mechanism heat exchange unit 21. Is done.

  FIG. 17 shows the fuel cell system according to the second embodiment, and is a diagram showing in more detail the portions of the anode buffer mechanism heating medium supply unit 25 and the cathode buffer mechanism heating medium supply unit 35 of FIG. FIG. 17 is a specific example in the case where the heat from the above heat source is once heat exchanged with the cooling water discharged from the stack 1 and introduced into the buffer mechanism. In FIG. 17, the same parts as those in FIG.

  In FIG. 17, the heat exchanger 204 of the anode buffer mechanism heating medium supply unit 25 and the heat exchanger 210 of the cathode buffer mechanism heating medium supply unit 35 correspond to the external heat exchanger 98 shown in FIG. .

  In FIG. 17, the cooling water from the stack 1 is introduced into the anode buffer mechanism heating medium supply unit 25 via the cooling water introduction pipe 201, and the heat medium carrying the heat from the heat source is introduced into the heat medium. It is introduced via the pipe 205. Then, in the heat exchanger 204 of the anode buffer mechanism heating medium supply unit 25, heat exchange between the introduced cooling water from the stack 1 and the introduced heat medium is performed, and the cooling water from the stack 1 is heated. The The anode buffer mechanism heating medium supply unit 25 supplies the cooling water heated in the heat exchanger 204 to the anode buffer mechanism heat exchange unit 21 via the anode heating medium flow path 6. The cooling water of the stack 1 that has exchanged heat with the anode buffer reserve water in the anode buffer mechanism heat exchange unit 21 returns to the anode buffer mechanism heating medium supply unit 25 via the anode heating medium flow path 6, and further heats the anode buffer mechanism. It is discharged from the medium supply unit 25 via the cooling water discharge pipe 206. On the other hand, the heat medium subjected to heat exchange in the heat exchanger 204 is discharged from the heat medium discharge pipe 202 via the heat medium amount adjustment valve 203.

  Similarly, in FIG. 17, the cooling water from the stack 1 is introduced into the cathode buffer mechanism heating medium supply unit 35 via the cooling water introduction pipe 207, and the heat medium carrying the heat from the heat source is provided. It is introduced via the heat medium introduction pipe 211. Then, in the heat exchanger 210 of the cathode buffer mechanism heating medium supply unit 35, heat exchange between the introduced cooling water from the stack 1 and the introduced heat medium is performed, and the cooling water from the stack 1 is heated. The The cathode buffer mechanism heating medium supply unit 35 supplies the cooling water heated in the heat exchanger 210 to the cathode buffer mechanism heat exchange unit via the cathode heating medium flow path 8. The cooling water of the stack 1 that has exchanged heat with the cathode buffer storage water in the cathode buffer mechanism heat exchange section returns to the cathode buffer mechanism heating medium supply section 35 via the cathode heating medium flow path 8, and further, the cathode buffer mechanism heating medium. It is discharged from the supply unit 35 via the cooling water discharge pipe 212. On the other hand, the heat medium subjected to heat exchange in the heat exchanger 210 is discharged from the heat medium discharge pipe 208 via the heat medium amount adjustment valve 209.

  As described above, in the fuel cell system of FIG. 17, the heat supply from the heat sources (1) to (4) to the anode buffer mechanism heat exchange unit 21 and the cathode buffer mechanism heat exchange unit carries the heat. This is performed by indirect conduction performed after heat exchange between the heat medium and the cooling water of the stack 1.

  As described above, a specific example in which the heat from the heat source is once heat-exchanged with the cooling water discharged from the stack 1 and introduced into the buffer mechanism, and the heat from the heat source is directly introduced into the buffer mechanism. A specific example has been described.

  In addition, each means in Embodiment 1-3 is not limited as long as the function is made the same.

  Hereinafter, the fuel cell system according to the first to third embodiments will be described more specifically with reference to examples. In addition, this invention is not limited to a following example.

(Example 1)
In Example 1, the fuel cell system described in Embodiment 1 is used. In addition, the buffer mechanism part separators 50 and 60 shown in FIG. 4 of the fuel cell system in the first embodiment were used by stacking an appropriate number of stages according to the required amount of water in the stack. The appropriate number of stages means that when the amount of water vapor supplied from the gas humidification system is reduced to 70% of the rated value from the state in which the stored water level is a specified value, from the verification experiment of the operating status of the applicant's fuel cell system. Although the shortage is based on the water capacity that can be supplied from the stockpiled water for 15 minutes continuously, it is not always necessary to observe this, and it is not limited.

  The stored water level is monitored by an optical level sensor 63 via a viewing window 62 provided on the end plate 51. Whenever the specified water level is reached, the anode buffer mechanism drain port connected to the level gauge of the end plate 51 24, the anode buffer mechanism drain valve 27 was opened and discharged for a certain period of time, and used as the operating water for the reformer of the fuel gas supply unit 2. The cathode side was also used as the operating water for the reformer.

The buffer mechanism separators 50 and 61 are made of the same glassy carbon (manufactured by Tokai Carbon Co., Ltd.) as the stack separators 40 and 41. Although not shown in the figure, the buffer mechanism separators 50 and 61 are insulated from each other through an end plate and an insulating plate. The stack electromotive force was conducted to the current collector plate. The basic specifications of stack 1 are as follows: electrode area 200 square centimeters, current density 0.2 A / square centimeter, number of stacked stages 45, fuel utilization rate (Uf) 75%, air utilization rate (Uo) 50% The initial operation voltage was about 0.74 V and the rated output was 1.32 KW. Under rated operating conditions, operation required approximately 20LM of SRG (CO ₂ concentration 23%) and 53LM of air on a dry basis. The flow path specifications of this stack are completely parallel flow, the cooling water flow path is provided approximately along the reaction gas flow path, and the rated cooling water volume is 1.8 L / min. When the water temperature was 60 ° C, a drainage temperature of about 69 degrees was obtained.

The reformer was operated at a reformer temperature of 630 ° C and S / C (steam / carbon ratio) of 3.0, and the actual measured gas dew point was 63 ° ± 2 ° during rated operation. It could exceed 70 degrees due to excessive evaporation of internal reserve water. Therefore, this fuel supply system does not require additional humidification of the anode gas, and no special anode gas humidifier is provided. Air supplied from a blower was used as the cathode gas. This is a membrane that uses a total heat exchanger with a total membrane area of 5000 cm ² (humidified membrane Nafion 112 DuPont) to humidify to 57 degrees of dew point by total heat exchange with off-air, and then uses the stack cooling wastewater as the water source and heat source. the membrane humidifier total area 1000 cm ^2, was used being humidified to a dew point of 63 degrees. The dew points of the anode gas and the cathode gas are monitored by an anode gas dew point meter and a cathode gas dew point meter, and this control fixed point is set to 62 degrees.

    The buffer mechanism was stacked in series in the stack and then thermally insulated, and when there was no additional heat supply, it was kept at the same temperature as the stack by stack heat dissipation. The reformer burner waste gas was directly used as the heat medium required for additional humidification. The reformer burner is basically an assist combustion mode in which the degassed off-gas is used as fuel, but the raw material city gas (13A) is used as auxiliary fuel. The raw fuel (13A) consumption during rated driving was about 4LM, and at this time, it was possible to operate independently with off-gas (hydrogen amount about 3LM) with almost no excess or deficiency. Combustion control of the heterogeneous reformer burner is a subprogram that can control the combustion amount by feeding back signals from the anode gas dew point meter in the buffer mechanism and the cathode gas dew point system to the optimum combustion control program for the reforming reaction itself. Made by the built-in remodeling program. As a result, when the dew point of the reaction gas decreased with respect to the control fixed point, the input amount of 13A as auxiliary fuel increased, and the burner waste heat could be increased directly.

Under the rated operating conditions described above, every time the supply dew point drops from the fixed point of 62 degrees, additional humidification of 0.25 g / min at the anode and 0.65 g / min at the cathode is required. Multiplied by approximately 0.55 Kcal / g) to calculate 0.14 kcal / min and 0.35 Kcal / min, respectively. Since the combustion heat of 13A is 11000Kcal / m ³ , the raw fuel flow rate required to raise the supply gas dew point once is at the anode (0.14 / 11000) * 1000 = 0.0127LM = 13ccm, at the cathode (0.35 / 11000) * 1000 = 0.0318LM = 32ccm, and the total was calculated to be about 1% of the rated raw fuel consumption.

    In the fuel cell humidification system having the above-described system, the stack drainage temperature can be lowered by increasing the stack cooling water amount, and the water vapor supply amount from the cathode hot water humidifier can be arbitrarily reduced. When the supply dew point from the cathode hot water humidifier is reduced to 60 ° C by this method (the amount of cooling water at this time is 2.6 LM, the stack discharge water temperature is 66.5 degrees). Although the dew point was insufficient, the measured value of the increase in raw fuel at this time was 130 ccm, which was approximately twice the calculated value (32 * 2 = 64 CCM). That is, the increase in the raw fuel flow rate is uniquely used for the reforming reaction to increase the amount of supplied hydrogen, and this increase is not consumed in the stack under constant current control but becomes off-gas, and finally burned by the burner. This combustion exhaust gas is introduced into the buffer mechanism section described above and becomes an additional heat source. In addition to the loss of reforming efficiency (about 80%), all of the heat radiation loss from pipe heat dissipation, buffer mechanism, etc. Including, the thermal efficiency for additional humidification was calculated to be about 50%. In this way, it was possible to compensate for several degrees of depletion of the supply gas by assist combustion of several percent to 10% of the rated raw fuel consumption.

    In the above system, the time constant from the refueling of the raw fuel to the increase of the dew point of the supply gas is approximately 2.5 minutes unless special control is performed. When the PID setting and PID automatic decision subroutine was added to the above-mentioned subprogram and rewritten, this time was shortened to about 1 minute, and more agile dew point compensation was possible.

    The conventional fuel cell system of the system diagram shown in FIG. 6 and the fuel cell system of Example 1 having the system shown in FIG. 1 and having the buffer mechanism of the form shown in FIG. 3 were comparatively operated.

  FIG. 18 shows a stack life characteristic comparison chart (change in cell average voltage) in the rated operation at this time. According to this test result, the system in the present Example 1 had still better life characteristics than the conventional product of the applicant of the present application. The reason for this is that, as described above, the reaction gas that has condensed in the piping and the substantial amount of water vapor has returned to the dew point above the battery temperature again at a distance that does not give the piping length for condensation on the stack 1. , The effect that the MEA 42 can be prevented from being dried substantially, and the aspect in which the total heat exchanger capacity is reduced mainly due to factors of the surrounding environment (the humidification capacity of the total heat exchanger is dependent on the ambient temperature) Thus, the buffering effect on the stack 1 was inferred when the internal temperature of the system decreased (that is, it was dependent on the outside air temperature).

  Further, FIG. 19 shows that both fuel cell systems were repeatedly operated for 4 hours at a current density of 0.2 A / square centimeter and 4 hours for a weak operation at 0.1 A / square centimeter (TDR = turndown ratio 50%). 1 shows the life characteristics when subjected to a load fluctuation endurance test of 8 hours per cycle. As is clear from this, there was a greater gap in the durability of both than the rated life test.

  In order to analyze this phenomenon, the total amount of water supplied from the anode gas humidifying unit 4 (measured value by dew point measurement) and the stored water level of the anode buffer mechanism storage unit 29 are measured, and the total amount of water required by the stack ( Plotted together with the calculated value from the battery reaction equation). FIG. 20 shows the result.

  From this plot, while the battery demands water immediately according to the load during the load increase phase, it takes time for the reformer to reach thermal equilibrium. Obviously not. For this reason, in the conventional example, when there is no buffer, it is clear that the stack is operated in a dry state during this period. On the other hand, when the buffer is provided, it is clear from the behavior of the water level that the necessary amount from the stored water is replenished to the stack during this period. It was understood that the difference between the two in the load-fluctuating life characteristics was the accumulation of the life deterioration due to the drying operation when the load increased.

(Example 2)
In Example 2, the fuel cell system described in Embodiment 2 is used. The operating conditions of the fuel cell system of Example 2 are shown below.

  The rated operating conditions are current density 0.2A / square centimeter MEA, fuel utilization rate (Uf) 75%, air utilization rate (Uo) 40%, the cooling water temperature flowing into the stack 1 is 70 degrees, and the cooling water is stuck The temperature in the branch valve 97 located at the portion discharged from 1 was monitored, and the flow rate was controlled so that it became 75 degrees. The flow rate at this time was about 3.5 liters / minute per 1 KW of stack output. there were.

  This branch valve 97 has a role of controlling the amount of cooling water flowing through the anode and cathode side heating medium flow paths 74 and 84 so that the stored water becomes a constant temperature. In the experiment of the second embodiment, the stored water is stored. The anode and cathode buffer mechanism control units 28 and 38 were controlled so that the water temperature was maintained at 72 degrees. In addition, an external heat exchanger 97 is provided in the heating medium passages 74 and 84 so that heat drawn from a heat source other than the stack can be replenished when the cooling water temperature is insufficient. It was possible to keep the stored water at 72 degrees without using it.

  The anode and cathode side heating medium channels 74 and 84 were formed by covering a SUS316L pipe (outer diameter 6.35 mm, wall thickness 1 mm) with a PFA tube and heat shrinking, and bending it. The material of this part requires special attention as described above in the case of a metal pipe because the fuel cell particularly dislikes heavy metal contamination, especially in the anode in a reducing atmosphere.

The fuel cell systems of Example 1 and Example 2 were assembled in the following three stacking stages, and the rated durability test was performed.
50 layers (stack length 300mm, rated 1.3kW)
100 layers (600mm, 2.6KW)
200-layer stack (1200mm, 5.2KW)
The result in Example 1 is shown in FIG. 21, and the result in Example 2 is shown in FIG. As is clear from this, in Example 2, compared with Example 1, particularly good results were obtained when the stack length was long.

  In order to verify the reason, the stack after 200-layer stacking and 1500 hours of operation is disassembled and counted from the buffer mechanism 20 and 30 side (in the second embodiment, counted from the end plate 90 side). Stage, 50th stage, 100th stage, 150th stage, 200th stage unit cell (the applicant's stack is composed of a single stage cell (single cell) as a subassembly and stacking them. The voltage under the above rated operating conditions was checked). The results are shown in Table 2.

  From this result, it has been found that in the first embodiment, the deterioration of the cell progresses as the latter stage, but in the second embodiment, no clear tendency is shown, and the deterioration is not promoted as compared with the first embodiment. As described above, this is understood as a problem of the distance from the water vapor supply unit, and in this example 2, an improvement was seen with respect to the example 1 in this respect.

  Using the fuel cell system of Example 2 as a comparative control, each load is equalized in the order of 0.05A → 0.2A → 0.4A (rated) → 0.8A → 0.4A → 0.2A → 0.05A. A load fluctuation endurance test was conducted over time. The graph of FIG. 23 shows the battery average voltage of each of Examples 1 and 2 when the load change is repeated, and the thick line shows the temporal average value. Using this temporal average value, the durability of Example 1 and Example 2 were compared. The present Example 2 was still improved compared to the Example 1, and the superiority of the present Example that the followability of the supplied water amount to the load was improved over the entire stack could be confirmed.

  The program of the present invention is a program for causing a computer to execute the functions of the control unit of the fuel cell system of the present invention described above, and is a program that operates in cooperation with the computer.

  The recording medium of the present invention is a recording medium carrying a program for causing a computer to execute all or part of the functions of the control unit of the above-described fuel cell system of the present invention. The recorded program executes the function in cooperation with the computer.

  Moreover, the function of the said control part of this invention means all or one part function.

  Further, one usage form of the program of the present invention may be an aspect in which the program is recorded on a computer-readable recording medium and operates in cooperation with the computer.

  Further, one usage form of the program of the present invention may be an aspect in which the program is transmitted through a transmission medium, read by a computer, and operated in cooperation with the computer.

  The recording medium includes a ROM and the like, and the transmission medium includes a transmission medium such as the Internet, light, radio waves, sound waves, and the like.

  The computer of the present invention described above is not limited to pure hardware such as a CPU, but may include firmware, an OS, and peripheral devices.

  As described above, the configuration of the present invention may be realized by software or hardware.

  The fuel cell system according to the present invention, the operation method thereof, and the like have the effect of more reliably maintaining the entire MEA region in water vapor saturation, and are useful as a home cogeneration fuel cell system and the like.

1 is a conceptual diagram of a fuel cell system according to a first embodiment of the present invention. 1 is a side view of a stack of a fuel cell system according to a first embodiment of the present invention. (A) Plan view of the separator of the fuel cell system according to the first embodiment of the present invention (b) Plan view of the separator of the fuel cell system according to the first embodiment of the present invention (c) Embodiment according to the present invention 1 is a side view of the separator of the fuel cell system in FIG. 1 is a configuration perspective view of a fuel cell system according to a first embodiment of the present invention. (A) Plan view of the buffer mechanism section separator of the fuel cell system according to the first embodiment of the present invention (b) Plan view of the buffer mechanism section separator of the fuel cell system according to the first embodiment of the present invention (c) 1 is a side view of a buffer mechanism separator of a fuel cell system according to a first embodiment of the invention. 1 is a side configuration diagram of a fuel cell system according to Embodiment 1 of the present invention. Conceptual diagram of a fuel cell system according to Embodiment 2 of the present invention. (A) Configuration perspective view of the fuel cell system according to the second embodiment of the present invention (b) Enlarged perspective view of the main part of the fuel cell system according to the second embodiment of the present invention (c) Embodiment according to the present invention 2 is an enlarged side view of the main part of the fuel cell system in FIG. Schematic of the fuel cell system in Embodiment 3 concerning this invention Schematic of the fuel cell system in Embodiment 3 concerning this invention Schematic of the fuel cell system in Embodiment 3 concerning this invention Schematic of the fuel cell system in Embodiment 3 concerning this invention Schematic of the fuel cell system in Embodiment 3 concerning this invention Schematic of the fuel cell system in Embodiment 3 concerning this invention Schematic of the fuel cell system according to Embodiment 3 of the present invention. FIG. 15 is a perspective view of the stack structure of the fuel cell system of FIG. 15 according to the third embodiment of the present invention. Schematic of the fuel cell system in Embodiment 3 concerning this invention The figure which shows the graph of the lifetime characteristic in the rated continuous operation of Example 1 concerning this invention and the conventional fuel cell system. The figure which shows the graph of the load fluctuation operation lifetime characteristic of the fuel cell system in Example 1 concerning this invention, and the conventional fuel cell system. The figure which shows the graph of the water balance at the time of the load change driving | operation of the fuel cell system in Example 1 concerning this invention. The figure which shows the graph of the stage number dependence of the lifetime characteristic comparison in the rated continuous operation of the fuel cell system in Example 1 concerning this invention. The figure which shows the graph of the stage number dependence of the lifetime characteristic comparison in the rated continuous operation of the fuel cell system in Example 2 concerning this invention. The figure which shows the graph of the load fluctuation operation lifetime characteristic of the fuel cell system in Example 2 and Example 3 concerning this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stack 2 Anode gas supply part 3 Cathode gas supply part 4 Anode gas humidification part 5 Cathode gas humidification part 6 Anode heating medium flow path 8 Cathode heating medium flow path 10 Heat insulating material 20 Anode buffer mechanism part 21 Anode buffer mechanism heat exchange part 22 Anode buffer mechanism water level detection unit 23 Anode buffer mechanism humidity detection unit 24 Drain port 25 Anode buffer mechanism heating medium supply unit 26 Anode buffer mechanism heating adjustment valve 27 Anode buffer mechanism drain valve 28 Anode buffer mechanism control unit 29 Anode buffer mechanism storage unit 30 Cathode buffer mechanism section 31 Cathode buffer mechanism heat exchange section 32 Cathode buffer mechanism water level detection section 33 Cathode buffer mechanism humidity detection section 34 Drain port 35 Cathode buffer mechanism heating medium supply section 6 cathode buffer mechanism heating adjusting valve 37 cathode buffer mechanism drain valve 38 cathode buffer mechanism control unit 39 cathode buffer mechanism reserve section

Claims (22)

An electrolyte membrane, a pair of gas diffusion electrodes disposed so as to sandwich the electrolyte membrane, and a gas or an oxidant gas disposed between the pair of gas diffusion electrodes from outside the pair of gas diffusion electrodes. A stack having a plurality of stacked unit cells having a separator formed with gas flow channel grooves for supplying to
A gas supply unit for supplying the gas to the stack;
A gas humidifying unit for humidifying the gas disposed between the gas supply unit and the gas flow channel groove;
The amount of water vapor contained in the gas supplied to the gas flow channel groove is more than the saturated water vapor amount at the temperature of at least one gas flow channel groove inlet portion of the gas diffusion electrode where the gas is first consumed. A fuel cell system including a control unit that performs control to increase the number of the fuel cells.   The fuel cell system according to claim 1, wherein the control unit controls the amount of water vapor contained in the gas so that the water vapor contained in the gas does not cause flooding in the electrolyte membrane. The control unit includes a buffer mechanism unit that is provided between the gas flow channel groove and the gas humidification unit and adjusts a water vapor amount of the gas supplied to the plurality of stacked unit cells. ,
The buffer mechanism is
A stockpiling unit that stocks moisture;
A heating unit for heating moisture stored in the storage unit;
A temperature detection unit for detecting the temperature of the stored water;
Supplying the moisture to be re-vaporized and supplied to the at least one electrode by controlling the heating unit so that the temperature of the moisture is kept higher than the temperature at the electrode entrance of the gas flow channel groove The fuel cell system according to claim 1, further comprising a control unit. An electrolyte membrane, a pair of gas diffusion electrodes disposed so as to sandwich the electrolyte membrane, and a gas or an oxidant gas disposed between the pair of gas diffusion electrodes from outside the pair of gas diffusion electrodes. A stack having a plurality of stacked unit cells having a separator formed with gas flow channel grooves for supplying to
A gas supply unit for supplying the gas to the stack;
A gas humidifying unit for humidifying the gas disposed between the gas supply unit and the gas channel groove;
A fuel cell system comprising a buffer mechanism provided between the gas flow channel groove and the gas humidifying unit and configured to adjust a water vapor amount of the gas supplied to the plurality of stacked unit cells. The buffer mechanism unit is a storage unit for storing water;
A heating unit for heating moisture stored in the storage unit;
A temperature detection unit for detecting the temperature of the stored water;
Control the heating unit so that the temperature of the moisture is kept higher than the temperature at the electrode entrance of the gas flow channel groove, and re-vaporize the moisture to supply the moisture to the at least one electrode The fuel cell system according to claim 4, further comprising: The stockpiling unit performs heat amount control for condensing water vapor supplied from the gas supply unit beyond the saturated water vapor amount at the internal temperature of the buffer mechanism unit,
The controller is
(1) Waste heat of reformer (2) Heat of fuel gas supplied from reformer to stack (3) Heat obtained by burning fuel (4) Residual exhaust from stack Heat obtained by burning fuel gas
(5) The fuel cell according to claim 5, wherein the condensed water vapor is vaporized by using at least one of heats of waste water of the cooling water discharged from the stack as a heat source. system.   The fuel cell system according to claim 6, wherein heat obtained by burning the fuel or residual fuel gas discharged from the stack is obtained from a reformer burner.   The fuel cell system according to claim 6, wherein the heat obtained by burning the fuel or the remaining fuel gas discharged from the stack is obtained from a dedicated combustor other than a reformer burner.   The control unit controls the amount of heat of the one or more heats introduced into the buffer mechanism unit based on a detection signal for detecting the amount of water vapor supplied to the stack, whereby the gas supplied to the gas flow channel groove 7. The fuel according to claim 6, wherein the amount of water vapor included in the gas diffusion electrode is controlled to be larger than a saturated water vapor amount at a temperature at the gas channel groove inlet portion where the gas is first consumed in the gas diffusion electrode. Battery system.   The fuel cell system according to claim 9, wherein the control unit performs heat amount control of the one or more heats by controlling a heat medium amount.   The fuel cell system according to claim 9, wherein the control of the amount of heat of the one or more heats by the control unit includes control of a combustion amount of the reformer or a dedicated combustor.   The fuel cell system according to claim 6, wherein the supply of the one or more heats to the control unit is performed by direct conduction of a thermal fluid from a heat source of the heat.   The fuel according to claim 6, wherein the supply of the one or more heats to the control unit is performed by indirect conduction after the heat fluid from the heat source of the heat exchanges heat with the stack cooling drainage. Battery system.   The fuel cell system according to claim 4, wherein a plurality of control constants of the control unit can be set corresponding to a plurality of operation modes.   The fuel cell system according to claim 4, wherein the control unit performs control by learning an optimal control constant in a use situation. A gas inlet manifold for supplying the gas to the gas flow channel groove;
The fuel cell system according to claim 4, wherein the buffer mechanism portion is disposed directly connected to the gas inlet manifold. A gas inlet manifold for supplying the gas to the gas flow channel groove;
The fuel cell system according to claim 4, wherein the buffer mechanism is provided in the gas inlet manifold.   The fuel cell system according to claim 4, wherein the stack and the buffer mechanism are collectively insulated. An electrolyte membrane, a pair of gas diffusion electrodes disposed so as to sandwich the electrolyte membrane, and a gas or an oxidant gas disposed between the pair of gas diffusion electrodes from outside the pair of gas diffusion electrodes. A stack having a plurality of stacked unit cells having a separator formed with gas flow channel grooves for supplying to
A gas supply unit for supplying the gas to the stack;
A fuel cell system operating method for operating a fuel cell system comprising a gas humidifying unit for humidifying the gas disposed between the gas supply unit and the gas flow channel groove,
The amount of water vapor contained in the gas supplied to the gas flow channel groove is larger than the saturated water vapor amount at the temperature at the gas flow channel groove inlet portion where the gas is first consumed in the gas diffusion electrode. A method for operating a fuel cell system, comprising a control step for performing control as described above. An electrolyte membrane, a pair of gas diffusion electrodes disposed so as to sandwich the electrolyte membrane, and a gas or an oxidant gas disposed between the pair of gas diffusion electrodes from outside the pair of gas diffusion electrodes. A stack having a plurality of stacked unit cells having a separator formed with gas flow channel grooves for supplying to
A gas supply unit for supplying the gas to the stack;
An operation method of a fuel cell system, comprising a gas humidifying unit for humidifying the gas disposed between the gas supply unit and the gas flow channel groove,
A method for operating a fuel cell system, comprising an adjustment step of adjusting an amount of water vapor of the gas supplied to the plurality of stacked unit cells between the gas flow channel groove and the humidifying unit.   2. The fuel cell system according to claim 1, wherein the amount of water vapor contained in the gas supplied to the gas flow channel groove is at the gas flow channel groove inlet portion of the gas diffusion electrode where the gas is first consumed. A program for causing a computer to function as a control unit that performs control so as to increase the amount of saturated water vapor at a temperature.   A recording medium on which the program according to claim 21 is recorded, wherein the recording medium can be processed by a computer.

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