JP2009170131A - Fuel cell power generation system and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell power generation system having an excellent power generation efficiency and durability. <P>SOLUTION: The fuel cell power generation system includes a fuel cell 4, a cooling water passage 5a where cooling water passes, a cooling water tank 7 for storing cooling water, a cooling water supplying pipe 5 for supplying the cooling water from the cooling water storing tank 7 to the cooling water passage 5a, and cooling water switching valves 9, 10 which are fixed in a passage of the cooling water supplying pipe 5 and switch the cooling water to cold water of a low temperature. When the cooling water switching valves 9, 10 switch the cooling water to the cold water and the cold water of a lower temperature than that of an operation temperature is supplied to the fuel cell through the cooling water passage 5a, a temperature of the fuel cell 4 is lowered quickly to generate condensed water in the fuel cell 4, and a water content of an electrolyte can be increased. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell power generation system that recovers the activity of a fuel cell and improves the power generation efficiency and durability of the system, and an operation method thereof.

  As shown in FIG. 5, a conventional general fuel cell power generation system is supplied from a fuel supply means 101 for supplying fuel gas, an oxidant gas supply means 102 for supplying oxidant gas, and a fuel supply means 101. The humidifying means 103 for humidifying the oxidant gas supplied from the fuel gas and oxidant gas supply means 102, the fuel cell 104 to which the fuel gas and oxidant gas humidified by the humidifying means 103 are supplied, and the fuel cell 104 A cooling water supply pipe 105 that circulates cooling water that cools the fuel and supplies hydrogen to the fuel cell 104 by humidifying the hydrogen as the fuel gas and the air as the oxidant gas.

  The fuel cell 104 includes a solid polymer electrolyte and a pair of electrodes formed on both sides thereof. By flowing a humidified fuel gas and oxidant gas, the electrolyte exhibits hydrogen ion conductivity, and protons pass through the electrolyte. Moves between the electrodes, and a current flows to generate electricity.

  However, the humidification of the fuel gas and the oxidant gas is insufficient, or the cooling of the fuel cell 104 is insufficient, so that the electrolyte becomes dry, and the fuel gas and the oxidant gas do not contain sufficient moisture. When this occurs, there is a problem that the hydrogen ion conductivity is reduced and the output is reduced.

  In addition, impurities used during the manufacture of the fuel cell 104, impurities contained in components used in the system, or impurities mixed from outside such as the air enter the fuel cell 104 and adhere to the electrodes, etc. Then, the chemical reaction required for electric power generation was inhibited, and there was a problem that the output decreased.

  Therefore, it is necessary to maintain the activity of the fuel cell 104 by keeping the water content of the electrolyte constant or removing impurities so that the output does not decrease. In addition, since the output may decrease gradually due to a decrease in moisture content or accumulation of impurities over time, the activity of the fuel cell 104 may be increased periodically or when the output exceeds a threshold value. It was necessary to recover.

  For example, as a method of maintaining or increasing the moisture content of the electrolyte, the amount of humidified moisture in the supplied fuel gas or oxidant gas is increased, the utilization rate of the fuel gas or oxidant gas is increased, and the generated water electrolyte is increased. Increase opportunities for contact with

  Further, as shown in FIG. 5, in order to increase the moisture content of the electrolyte, the heat of the cooling water supplied to the fuel cell 104 is radiated using the radiator 106 or the like, and the cooling water whose temperature has been lowered is supplied to the fuel cell 104. By supplying, the temperature of the fuel cell 4 was lowered, the relative humidity of the fuel gas and the oxidant gas was increased, and the moisture content of the electrolyte was increased (for example, see Patent Document 1).

  As a method for preventing impurities from entering the fuel cell 104, the manufacturing environment is kept clean, the use of components and materials containing impurities is restricted, and impurities are removed by washing, adsorption, decomposition, etc. And so on.

For example, deionized water, weakly acidic water, or the like is introduced into the fuel cell 104 and boiled to clean and remove impurities (see, for example, Patent Document 2).
Japanese Patent No. 3687530 Japanese Patent No. 3469091

  However, the heat of the cooling water supplied to the conventional fuel cell 104 is dissipated using the radiator 106 or the like, and the cooling water whose temperature has been lowered is supplied to the fuel cell 4, thereby lowering the temperature of the fuel cell 104. In the method of increasing the water content of the electrolyte by increasing the relative humidity of the fuel gas and the oxidant gas, it takes a long time for the water content of the electrolyte to stabilize because the cooling water spends a lot of time radiating heat. There was a problem.

  In addition, in the conventional method in which deionized water, weakly acidic water, or the like is introduced into the fuel cell 104 and boiled to wash away impurities, the impurities mixed after being mounted on the fuel cell power generation system cannot be removed. There was a problem.

  The present invention solves the above-described conventional problems, and includes a cooling water switching valve for switching to cooling water having a lower temperature than cooling water in a path of a cooling water supply pipe for supplying cooling water in order to lower the temperature of the fuel cell. Switch the water switching valve to the cold water side, supply cold water to the cooling water flow path of the fuel cell, quickly reduce the temperature of the fuel cell, increase the moisture content of the electrolyte with the generated condensed water, and wash away impurities Accordingly, an object of the present invention is to provide a fuel cell power generation system that activates a fuel cell and is excellent in power generation efficiency and durability, and an operation method thereof.

  In order to achieve the above object, the present invention provides a fuel cell, a cooling water passage for circulating cooling water for cooling the fuel cell, a cooling water tank for storing the cooling water, and a cooling water flow from the cooling water tank. A cooling water supply pipe that supplies the cooling water to the passage, and a cooling water switching valve that is attached to a path of the cooling water supply pipe and switches the cooling water to cold water having a temperature lower than that of the cooling water.

  According to the configuration of the present invention, the cooling water switching valve switches the cooling water to cold water, supplies cold water having a temperature lower than the operating temperature to the fuel cell to the cooling water flow path, and quickly reduces the temperature of the fuel cell, Condensed water can be generated therein, the water content of the electrolyte can be increased, impurities can be washed away, the fuel cell can be activated, and a fuel cell power generation system with excellent power generation efficiency and durability can be obtained.

  According to the present invention, since the activity of the fuel cell can be recovered by the above-described configuration, it is possible to provide a fuel cell power generation system excellent in power generation efficiency and durability and an operation method thereof.

  A first aspect of the invention includes a fuel cell, a cooling water passage for circulating cooling water for cooling the fuel cell, a cooling water tank for storing the cooling water, and the cooling water from the cooling water tank to the cooling water passage. And a cooling water switching valve that is attached to a path of the cooling water supply pipe and switches the cooling water to cold water having a temperature lower than that of the cooling water. Is switched to cold water, and cold water having a temperature lower than the operating temperature is supplied to the fuel cell to the cooling water flow path, the temperature of the fuel cell is rapidly reduced, condensed water is generated in the fuel cell, and the water content of the electrolyte is increased. Impurities can be washed away, the fuel cell can be activated, and a fuel cell power generation system having excellent power generation efficiency and durability can be obtained.

  According to a second aspect of the present invention, in the first aspect, by supplying cold water from tap water, room temperature tap water such as city water can be directly supplied without passing through storage equipment such as a tank or a heat exchanger such as a radiator. By supplying it to the cooling water flow path, the temperature of the fuel cell can be quickly reduced, and not only can the system be simplified, but there is no need for fans associated with heat exchangers or auxiliary equipment such as cooling equipment. Therefore, power consumption can be saved and the power generation efficiency of the system can be improved.

  According to a third aspect of the present invention, in the first aspect of the invention, the cold water purifying means is provided for purifying the cold water, and impurities such as metal ions contained in the cold water such as tap water are purified and supplied, whereby the ionic conduction of the cold water is achieved. Since the increase in the rate is suppressed, it is possible to prevent the carbon separator or the like from being decomposed by electrolytic corrosion.

  According to a fourth aspect, in the first aspect, the flow rate control means for controlling the flow rate of the chilled water is provided, and the flow rate control means controls the flow rate of the chilled water so that a difference between the inlet temperature and the outlet temperature of the cooling water flow path becomes small. As a result, not only can the temperature of the fuel cell be quickly reduced, but the temperature distribution in the electrode surface of the fuel cell becomes uniform and the entire surface is activated, so that the power generation efficiency can be improved. it can.

  According to a fifth invention, in the first invention, a heat exchanger for exchanging heat with the cooling water supplied to the fuel cell, a hot water storage tank for storing hot water exchanged by the heat exchanger, and hot water for the hot water storage tank The hot water storage pump is stopped while the cold water is circulating in the cooling water flow path, thereby obtaining a system with little loss of thermal efficiency without lowering the temperature of the hot water in the hot water storage tank. be able to.

  According to a sixth invention, in the first invention, a heat exchanger for exchanging heat with the cooling water supplied to the fuel cell, a hot water storage tank for storing hot water heat-exchanged by the heat exchanger, and an upstream of the hot water storage tank A hot water storage tank switching valve disposed on the side of the hot water storage tank, the hot water tank switching valve introduces hot water that is heat-exchanged into the upper part of the hot water storage tank while the cooling water is flowing through the cooling water flow path, and the cooling water flow path While cold water is circulating, by switching the hot water that has been circulated through the heat exchanger to be introduced into the lower part of the hot water storage tank, cold water and hot hot water can be separated vertically in the hot water storage tank, A system with little thermal efficiency loss can be obtained without lowering the temperature of hot water to be supplied.

  According to a seventh invention, in the first invention, there is provided voltage detecting means for detecting the voltage of the fuel cell, and the voltage detecting means detects that the voltage of the fuel cell has exceeded a preset threshold value for a predetermined time or more. When the cooling water switching valve is switched so that cold water having a temperature lower than that of the cooling water is supplied to the cooling water flow path, the voltage of the fuel cell is lowered, and only when it is determined that the activity of the fuel cell is lowered, Since cold water is supplied to the road, loss of thermal efficiency due to cold water having a low temperature can be minimized.

  According to an eighth aspect of the present invention, in the first aspect of the invention, the fuel cell includes voltage detection means for detecting the voltage of the fuel cell, and the fuel cell is generating power and while cooling water having a temperature lower than that of the cooling water is supplied to the cooling water flow path. When the voltage detection means detects that the voltage of the fuel cell has exceeded a preset lower limit value, by switching the cooling water switching valve so that the cooling water is supplied to the cooling water flow path, When the amount of production is large, the temperature of the fuel cell can be raised to reduce the amount of condensed water, and deterioration of characteristics such as flooding can be suppressed.

  According to a ninth aspect of the invention, there is provided a fuel cell, a cooling water passage for circulating cooling water for cooling the fuel cell, a cooling water tank for storing the cooling water, and the cooling water from the cooling water tank to the cooling water passage. A cooling water supply pipe that supplies the cooling water, a cooling water switching valve that is attached to a path of the cooling water supply pipe and switches the cooling water to cold water having a temperature lower than that of the cooling water, and a fuel gas and an oxidant supplied to the fuel cell Humidifying means for humidifying the gas, condensing the fuel gas and the oxidant gas condensed by the humidifying means with the cold water supplied to the cooling water flow path by switching the cooling water switching valve to condense water The operation method of recovering the activity of the fuel cell by supplying the condensed water to the fuel cell and rapidly reducing the temperature of the fuel cell, generating condensed water in the fuel cell, Of increasing the water content, impurities can be washed away, the fuel cell is activated, it is possible to obtain excellent fuel cell power generation system in the power generation efficiency and durability.

  Further, the generated water generated by the power generation is also condensed by the cold water, and the relative humidity is further increased. Therefore, the fuel cell is further activated, and a fuel cell power generation system excellent in power generation efficiency and durability can be obtained.

  According to a tenth aspect, in the ninth aspect, among the humidified fuel gas and oxidant gas, at least the supply of the oxidant gas is stopped to stop power generation, and the cooling water is reduced while lowering the voltage of the fuel cell. Switching the switching valve to condense the fuel gas and the oxidant gas remaining in the cold water supplied to the cooling water flow path to generate condensed water, and supplying the condensed water to the fuel cell to activate the fuel cell When the fuel cell power generation is stopped, the condensed water increases the water content of the electrolyte and the impurities can be removed by washing, and the fuel cell is activated and the oxidant gas is supplied at the same time. Since the potential of the electrode is lowered and the catalyst in the electrode is reduced, the fuel cell can be further activated.

  According to an eleventh aspect of the present invention, in the ninth or tenth aspect of the invention, after the load is cut off and the circuit is once opened, at least the supply of the oxidant gas among the humidified fuel gas and oxidant gas is stopped. In the open circuit state, the potential of the electrode to which the oxidant gas was supplied is raised, the impurities attached to the catalyst in the electrode are oxidized and easily removed, and the condensed water is washed. Since the effect is promoted, the fuel cell can be more activated.

  A twelfth aspect of the invention is the ninth aspect of the invention, in which the cooling water switching valve is switched and supplied to the cooling water flow path to start power generation, the fuel gas and the oxidant gas are condensed to generate condensed water, After the condensed water is supplied to the fuel cell and the activity of the fuel cell is restored, the cooling water switching valve is switched to supply the cooling water to the cooling water flow path. Can increase the moisture content of the electrolyte that is dried during the shutdown, clean and remove impurities adhering during the shutdown, and activate the fuel cell. A fuel cell power generation system excellent in efficiency and durability can be obtained.

  In a thirteenth invention according to the ninth or twelfth invention, the cooling water switching valve is switched to supply cold water having a temperature lower than that of the cooling water to the cooling water flow path, to supply humidified fuel gas and oxidant gas, and to open once. After switching to the circuit state, the operation method of starting power generation raises the potential of the electrode to which the oxidant gas is supplied in the open circuit state, and oxidizes impurities attached to the catalyst in the electrode to make it easier to remove. In addition, since the cleaning effect of the condensed water is promoted, the fuel cell can be more activated, a higher voltage is maintained than at the start of power generation, and a fuel cell power generation system with excellent power generation efficiency and durability can be obtained. .

  In a fourteenth aspect based on any one of the ninth to thirteenth aspects, the power generation is stopped by stopping the supply of at least the oxidant gas out of the humidified fuel gas and oxidant gas, and the voltage of the fuel cell The cooling water switching valve is switched while the cooling water is lowered to condense the fuel gas and the oxidant gas remaining in the cooling water supplied to the cooling water flow path to generate condensed water, and supply the condensed water to the fuel cell. Then, while supplying the cold water to the cooling water flow path, the humidified fuel gas and the oxidant gas are supplied to start power generation, and the fuel gas and the oxidant gas are condensed to generate condensed water. And supplying the condensed water to the fuel cell to restore the activity of the fuel cell, and then switching the cooling water switching valve to start and stop supplying the cooling water at least once. The recovery operation method improves the efficiency of moisture content increase due to condensed water and the cleaning effect of impurities, and the increase and decrease of the potential due to start and stop promotes activation by oxidizing and reducing the catalyst, so power generation efficiency and durability are improved. An excellent fuel cell power generation system can be obtained.

  In a fifteenth aspect of the invention, according to any one of the ninth to fourteenth aspects, when power is generated for the first time after the system is installed, the cooling water switching valve is switched to supply cold water to the cooling water flow path, and the fuel gas and the oxidation are supplied. The system is actually installed after the system is installed by an operation method that condenses the agent gas to generate condensed water, supplies the condensed water to the fuel cell, and recovers the activity of the fuel cell at least once. Before use, the water content of the electrolyte dried while the condensate is stopped can be increased, the impurities attached during the stop can be removed by washing, and the fuel cell is activated so that the user can use it for the first time. A high voltage can be maintained from time to time, and a fuel cell power generation system excellent in power generation efficiency and durability can be obtained.

  In a sixteenth aspect of the invention, according to any one of the ninth to fourteenth aspects, after the system has been stopped for a long period of time, the cooling water switching valve is switched to supply cold water to the cooling water flow path before generating power, and fuel gas and oxidation Due to the operation method of condensing the agent gas to generate condensed water, supplying the condensed water to the fuel cell and recovering the activity of the fuel cell at least once, the system is not used for a long period of time. In the meantime, the water content of the electrolyte dried while the condensate is stopped can be increased, the impurities attached during the stop can be washed away and the fuel cell can be activated. A fuel cell power generation system that can be retained and has excellent power generation efficiency and durability can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 shows a schematic configuration diagram of a fuel cell power generation system according to Embodiment 1 of the present invention.

  The fuel cell power generation system according to Embodiment 1 of the present invention includes a fuel supply means 1 for reforming a raw material gas such as a city gas containing hydrocarbons such as methane and supplying a fuel gas, and an oxidation for supplying an oxidant gas. Coolant gas supply means 2, humidifying means 3 for humidifying the oxidant gas, fuel cell 4 to which the humidified fuel gas and oxidant gas are supplied, and cooling water supply for circulating the coolant for cooling the fuel cell 4 A tube 5 is provided.

  The fuel supply means 1 includes a desulfurization unit 1a that adsorbs and removes sulfur compounds contained in an odorant and the like, a reforming unit 1b that reforms a raw material gas containing hydrocarbons such as methane, and the like that is generated by a reforming reaction. A CO conversion unit 1c that converts carbon oxide (CO) and a CO removal unit 1d that oxidizes and removes CO are supplied to the anode side of the fuel cell 4 at least with a fuel gas containing hydrogen.

  The raw material gas is first desulfurized in the desulfurization section 1a and then reformed in the reforming section 1b to become a fuel gas containing hydrogen. When methane is used as the raw material gas, in the reforming unit 1b, the reaction shown by (Chemical Formula 1) occurs with water vapor, and about 10% of CO is generated together with hydrogen as the fuel gas.

(Scientific formula 1) CH ₄ + H ₂ O → CO + 3H ₂
Since the platinum catalyst contained in the anode in the operating temperature range of the fuel cell is poisoned even by a slight amount of CO and its catalytic activity is reduced, the CO generated in the reforming unit 1b is expressed as (CO 2) as shown in (Chemical Formula 2). Is converted to carbon dioxide, and its concentration is reduced to about 5000 ppm. In the downstream CO removing unit 1d, not only CO but also hydrogen of the fuel gas is oxidized, so that the CO concentration needs to be reduced as much as possible in the CO conversion unit 1c.

(Chemical formula 2) CO + H ₂ O → CO ₂ + H ₂
Further, the remaining CO is oxidized by reacting with oxygen contained in the air in the CO removing section 1d as shown in (Chemical Formula 3), and the concentration thereof is reduced to about 10 ppm or less which can suppress the deterioration of the catalytic activity of the anode.

(Chemical formula 3) CO + 1/2 O ₂ → CO ₂
The overall reaction formula is shown in (Chemical Formula 4).

(Chemical formula 4) CH ₄ + 2H ₂ O → CO ₂ + 4H ₂
The oxidant gas supply means 2 includes a blower 2 a that takes in the oxidant gas and an impurity removal means 2 b that removes impurities in the oxidant gas. The oxidant gas humidified by the humidification means 3 is supplied to the cathode side of the fuel cell 4. To supply.

  The oxidant gas is a general term for gases containing at least oxygen (or capable of supplying oxygen), and includes, for example, the atmosphere (air).

  The fuel cell 4 includes a membrane-shaped solid polymer electrolyte 4a made of a perfluorocarbon sulfonic acid polymer having hydrogen ion conductivity, a pair of electrodes formed on both surfaces of the electrolyte 4a, an anode 4b and a cathode 4c, an anode 4b, A pair of gaskets (not shown) provided around the cathode 4c to prevent gas mixing and leakage, and a gas passage for supplying and discharging fuel gas and oxidant gas to and from the anode 4b and cathode 4c, respectively. A unit cell composed of a pair of conductive separator plates 4d and 4e, and a plurality of unit cells and a cooling water flow path 5a for supplying and discharging cooling water are alternately stacked, and a current collecting plate, an insulating plate and a large load are applied to both ends. Equipped with an end plate made of high-strength metal that can withstand, firmly tightened with a fastening rod to prevent heat dissipation and stabilize temperature It constituted insulation for holding placed around.

  The anode 4b and the cathode 4c are composed of a catalyst layer made of a mixture of a catalyst in which noble metal such as platinum is supported on porous carbon and a polymer electrolyte having hydrogen ion conductivity, and air permeability and electrons laminated on the catalyst layer. It consists of a gas diffusion layer having conductivity. For the anode 4b, an alloy catalyst such as platinum-ruthenium having CO resistance was used. Moreover, carbon paper or carbon cloth subjected to water repellent treatment was used for the gas diffusion layer.

  Upstream of the cooling water supply pipe 5, cooling water purification means 6 that removes impurities and metal ions contained in the cooling water, a cooling water tank 7 that stores cooling water, and cooling that controls and circulates the cooling water flow rate. The water pump 8 is configured to supply the cooling water to the cooling water flow path 5a of the fuel cell 4 through the cooling water supply pipe 5, thereby controlling the temperature of the fuel cell 4 to the operating temperature. The cooling water purification means 6 includes activated carbon, ion exchange resin, and the like, purifies the cooling water, and keeps the conductivity of the cooling water low.

  Furthermore, the fuel cell power generation system according to Embodiment 1 of the present invention supplies cooling water and cold water to the path of the cooling water supply pipe 5 in order to supply cold water that controls the temperature of the fuel cell 4 to a temperature lower than the operating temperature. Cooling water switching valves 9 and 10 for switching are provided, and the cooling water switching valve 9 is switched to the cold water side so that the temperature of the fuel cell 4 can be quickly reduced. Further, while the cold water is being supplied to the fuel cell 4, the cooling water switching valve 10 is switched to the discharge side so that the temperature of the cooling water does not decrease, thereby preventing the cold water from entering the cooling water tank 7. It has a structure that can be done.

  Cold water is supplied to the direct cooling water flow path 5a of the fuel cell 4 without using storage water such as a tank or a heat exchanger such as a radiator. The temperature of the fuel cell 4 can be quickly reduced, and not only can the system be simplified, but there is no need for fans such as heat exchangers or auxiliary equipment such as cooling equipment, saving power consumption. This can improve the power generation efficiency of the system.

  In addition, the path for supplying cold water is equipped with cold water purification means 11 made of activated carbon, ion exchange resin, etc., and removes impurities and metal ions contained in the cold water to keep the conductivity of the cold water low. The carbon separator plates 4d and 4e can be prevented from being decomposed by electrolytic corrosion.

  Further, a flow rate control means 12 for controlling the flow rate of the cold water is provided downstream of the cold water purification means 11 so that the difference between the temperature of the cooling water inlet 13 of the cooling water flow path 5a of the fuel cell 4 and the temperature of the cooling water outlet 14 becomes small. Thus, not only can the temperature of the fuel cell 4 be quickly reduced, but also the temperature distribution in the surfaces of the electrodes 4b and 4c becomes uniform, and the entire surface is activated. Therefore, the power generation efficiency can be improved.

  Further, a heat exchanger 15 capable of exchanging heat with the cooling water is provided downstream of the cooling water outlet 14 of the fuel cell 4, and a hot water storage tank 16 for storing the hot water exchanged by the heat exchanger 15 is provided. A hot water storage pump 17 that circulates the hot water in the hot water storage tank 16 is provided, and the hot water storage pump 17 is stopped while cold water is being supplied to the fuel cell 4 so that hot water does not circulate.

  By stopping the hot water storage pump 17, the temperature of the hot water in the hot water storage tank 16 does not decrease, so that a system with little thermal efficiency loss can be obtained.

  Also, voltage detecting means 18 for detecting the voltage of the fuel cell 4 is connected to both ends of the fuel cell 4, and when the voltage detecting means 18 detects that the voltage of the fuel cell 4 has exceeded a preset threshold value for a predetermined time or more. The cooling water switching valves 9 and 10 can be switched so that the cooling water flow path 5a is supplied with the cooling water controlled to a temperature lower than the operating temperature. Therefore, since the cold water is supplied to the cooling water passage 5a only when it is determined that the voltage of the fuel cell 4 is lowered and the activity of the fuel cell 4 is lowered, it is possible to minimize the thermal efficiency loss due to the cold water having a low temperature. it can.

  Further, the voltage detection means 18 is configured so that the voltage of the fuel cell 4 exceeds the preset lower limit value while the fuel cell 4 is generating power and cold water lower than the operating temperature is supplied to the cooling water passage 5a. When this is detected, the cooling water switching valves 9 and 10 can be returned so that the cooling water controlled to the operating temperature is supplied to the cooling water flow path 5a. Accordingly, when the temperature of the fuel cell 4 is low, the amount of condensed water generated is large, and the voltage of the fuel cell 4 is low enough to exceed the lower limit, the temperature of the fuel cell 4 can be raised to reduce the amount of condensed water, and flooding It is possible to suppress deterioration of characteristics such as.

  The operation of the fuel cell power generation system of the present invention having the above configuration will be described. When a fuel gas and an oxidant gas are supplied to the anode 4b and the cathode 4c, respectively, and a load is connected, hydrogen contained in the fuel gas supplied to the anode 4b emits electrons at the interface between the anode 4b and the electrolyte 4a to form hydrogen ions. This reaction formula is as shown in (Chemical Formula 5).

(Chemical Formula 5) H ₂ → 2H ⁺ 2e ⁻
The hydrogen ions move to the cathode 4c through the electrolyte 4a, receive electrons at the interface between the cathode 4c and the electrolyte 4a, react with oxygen contained in the oxidant gas supplied to the cathode 4c, and generate water. . This reaction formula is as shown in (Chemical Formula 6).

(Chemical formula 6) 1 / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O
The total reaction is shown in (Chemical Formula 7).

(Chemical Formula 7) H ₂ + 1 / 2O ₂ → H ₂ O
At this time, the flow of electrons flowing through the load can be used as direct current electric energy. Moreover, since a series of reactions are exothermic reactions, the reaction heat can be used as thermal energy.

  Here, the humidification of the fuel gas or the oxidant gas is insufficient, the cooling of the fuel cell 4 is insufficient, and the polymer electrolyte contained in the electrolyte 4a and the catalyst layer becomes dry, When water is not sufficiently contained, hydrogen ion conductivity may be reduced and power generation performance may be reduced. In addition, the moisture content may be reduced during initial operation or when left for a long period of time, and power generation performance may be reduced.

  However, in the fuel cell power generation system according to Embodiment 1 of the present invention, the cooling water switching valves 9 and 10 switch the cooling water to the cold water and supply the cold water to the fuel cell 4, so that the temperature of the fuel cell 4 is quickly reduced. It is possible to generate condensed water in the fuel cell 4 and increase the water content of the electrolyte 4a with the generated condensed water.

  Further, when impurities such as various organic solvents, surfactants, organic substances such as fats and oils are mixed in the fuel cell 4, the chemical reaction is hindered, so that the voltage of the fuel cell 4 is reduced, or the electrolyte 4a and the catalyst layer have The wettability (wetability with water) of the contained polymer electrolyte may be reduced, or the ion exchange characteristics may be reduced, thereby reducing the power generation performance.

  For example, when an organic solvent such as alcohol, which is a solvent component such as a coating ink for forming the catalyst layer of the electrode 4b or 4c, remains in the catalyst layer in the manufacturing process of the fuel cell 4, oil and fat in the atmosphere during the manufacturing process. When impurities adhere to the electrode surface, or when impurities such as organic matter are mixed in from the constituent materials such as the sealing material and resin material during power generation, stopping and storage of the fuel cell 4, impurities such as organic matter are oxidized from the outside. The case where it is carried together with the agent gas and mixed is mentioned.

  However, in the fuel cell power generation system according to Embodiment 1 of the present invention, the cooling water switching valves 9 and 10 switch the cooling water to the cold water and supply the cold water to the fuel cell 4, so that the temperature of the fuel cell 4 is quickly reduced. In addition, condensed water can be generated in the fuel cell 4, and impurities attached to the electrodes 4b and 4c and the like can be washed away with the generated condensed water and discharged.

  Next, an operation method of the fuel cell power generation system according to Embodiment 1 of the present invention will be described with reference to the flowchart of FIG.

  FIG. 2 shows a sequence when the fuel cell 4 is activated during the power generation of the fuel cell 4.

  First, it is confirmed that the fuel cell 4 is generating power, and that the coolant that controls the fuel cell 4 to the operating temperature is supplied from the coolant tank 7 to the coolant channel 5a (step 101).

  When the voltage detector 18 detects that the voltage of the fuel cell 4 is equal to or lower than a preset threshold value (step 102), the cooling water switching valve 9 is switched to the cold water side lower than the operating temperature of the fuel cell 4. Then, cold water is supplied to the cooling water flow path 5a of the fuel cell 4 (step 103).

  At this time, the cooling water switching valve 10 at the cooling water outlet 14 is switched to the discharge side so that the cooling water is not mixed into the cooling water tank 7. When a preset time has elapsed (step 104), the cooling water switching valves 9 and 10 are switched to the cooling water side to complete the activation (step 105).

  Condensed water is generated and the fuel cell 4 can be activated by supplying cold water to the fuel cell 4 and rapidly reducing the temperature during power generation by the above sequence. FIG. 3 shows a voltage change before and after activating the fuel cell 4 by supplying cold water. After activation, it was found that the voltage of the fuel cell 4 increased by 4 to 5%, and the power generation efficiency increased.

  Therefore, according to the fuel cell power generation system and the operation method thereof according to the first embodiment of the present invention, condensed water is generated, the moisture content of the electrolyte 4a is increased, and impurities are washed and removed, so that the fuel cell is activated, A fuel cell power generation system having excellent power generation efficiency and durability can be obtained.

(Embodiment 2)
Next, an operation of the method for activating the fuel cell 4 at the time of stopping and starting using the same fuel cell power generation system as that of Embodiment 1 of the present invention will be described for each step using the flowchart of FIG.

  In FIG. 4, first, it is confirmed that the fuel cell 4 is generating electric power, and that the cooling water for controlling the fuel cell 4 to the operating temperature is supplied from the cooling water tank 7 to the cooling water channel 5a (step 201). .

  When the voltage detector 18 detects that the voltage of the fuel cell 4 is equal to or lower than a preset threshold value (step 202), the cooling water switching valve 9 supplies cold water lower than the operating temperature of the fuel cell 4. The cold water is supplied to the cooling water flow path 5a of the fuel cell 4 (step 203). At this time, the cooling water switching valve 10 at the cooling water outlet 14 is switched to the discharge side so that the cooling water is not mixed into the cooling water tank 7.

  Then, the load connected to the fuel cell 4 is disconnected, and power generation is stopped (step 204). At this time, the fuel gas and the oxidant gas are flowing through the anode 4b and the cathode 4c, respectively.

  Then, after the voltage detector 18 detects that the voltage of the fuel cell 4 is in an open circuit state (step 205), the supply of the oxidant gas supplied to the cathode 4c is stopped (step 206). By setting the open circuit state, the potential of the catalyst surface of the cathode 4c is increased, and the impurities adhering to the cathode 4c are oxidized and easily dissolved in the condensed water, thereby enhancing the cleaning effect.

  When the supply of the oxidant gas is stopped, oxygen in the oxidant gas reacts with hydrogen contained in the fuel gas that cross leaks from the anode 4b side and is not consumed. Then, the catalytic surface of the cathode 4c can be reduced to increase the catalytic activity.

  Then, the voltage detection means 18 detects that the voltage at the time of stop is equal to or less than a preset threshold value (step 207). The activation method up to step 207 is performed when the fuel cell 4 is stopped. Here, the same effect can be obtained even when the fuel gas is stopped and the system is shut down.

  FIG. 4 shows the steps in the case where the start-up is continued and the activation is also performed at the start-up. In order to start the power generation, the oxidant gas is supplied while the fuel gas is supplied to the anode 4b. Start (step 208).

  At this time, the cooling water switching valves 9 and 10 are on the cold water side, cold water is supplied to the cooling water flow path 5a of the fuel cell 4, and the fuel cell 4 is at a low temperature. Then, after the voltage detector 18 detects that the voltage of the fuel cell 4 is in an open circuit state (step 209), the load is connected and power generation is started (step 210).

  By setting the open circuit state immediately before power generation, the potential of the cathode 4c increases, and the impurities adhering to the catalyst of the cathode 4c can be oxidized and removed easily, and the cleaning effect of condensed water can be promoted. . Then, the number of cycles from when power generation is stopped to when power is generated again is set to one, and when it is completed, the number of cycles is counted up (step 211).

  The steps from step 204 to step 211 are repeated, and when the number of cycles reaches a preset number (step 212), the cooling water switching valves 9 and 10 are switched to the cooling water side (step 213), and the fuel cell 4 The activation of is finished.

  According to the above sequence, stop and power generation are repeated while supplying cold water to the fuel cell 4 to raise and lower the potential of the cathode 4c, so that the effect of cleaning impurities can be enhanced and the fuel cell 4 can be activated.

(Embodiment 3)
The third embodiment of the present invention differs from the first embodiment in that a hot water storage tank switching valve 19 is provided upstream of the hot water storage tank 16 while the cooling water supply pipe 5 supplies the cooling water to the fuel cell 4. Hot water that has been heat-exchanged by the heat exchanger 15 is supplied to the upper part 20 of the hot water storage tank, and hot water circulated through the heat exchanger 15 is introduced to the lower part 21 of the hot water storage tank while cold water is being supplied to the fuel cell 4. It is the point which comprised so that the switching valve 19 might be switched.

  According to the above configuration, since hot water and cold water have different specific gravities, hot water can be separated into the upper part 20 of the hot water storage tank, and cold water can be separated into the lower part 21 of the hot water storage tank. The hot water storage tank switching valve 19 is switched so as to introduce hot hot water whose heat has been exchanged at the operating temperature of the fuel cell 4 into the upper part 20 of the hot water storage tank and cold water which has not been heat exchanged into the lower part 21 of the hot water storage tank. it can.

  Therefore, even when cold water having a low temperature flows through the fuel cell 4, heat can be exchanged by the heat exchanger 15 and stored in the hot water storage tank 16, so that the heat efficiency loss can be reduced without lowering the temperature of the hot water to be supplied. A few systems can be obtained.

  The fuel cell power generation system and the operation method thereof according to the present invention have the effect of increasing the moisture content of the electrolyte and activating the fuel cell by washing and removing impurities, improving the power generation efficiency and durability, This is useful for a fuel cell and a fuel cell device using a solid electrolyte membrane. It can also be used in stationary fuel cell cogeneration systems that can directly use tap water.

1 is a schematic configuration diagram of a fuel cell power generation system according to Embodiment 1 of the present invention. Flow chart showing the operation method of the system Characteristic diagram showing voltage change before and after activation by the system The flowchart which shows the operation method at the time of the stop of the fuel cell power generation system in Embodiment 2 of this invention, and electric power generation Schematic configuration diagram of a conventional fuel cell power generation system

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel supply means 1a Desulfurization part 1b Reforming part 1c CO conversion part 1d CO removal part 2 Oxidant gas supply means 2a Blower 2b Impurity removal means 3 Humidification means 4 Fuel cell 4a Solid polymer electrolyte 4b Anode 4c Cathode 4d, 4e Separator Plate 5 Cooling water supply pipe 5a Cooling water flow path 6 Cooling water purifying means 7 Cooling water tank 8 Cooling water pump 9, 10 Cooling water switching valve 11 Cooling water purifying means 12 Flow rate controlling means 13 Cooling water inlet 14 Cooling water outlet 15 Heat exchanger 16 Hot water storage tank 17 Hot water storage pump 18 Voltage detection means 19 Hot water storage tank switching valve 20 Upper part of hot water storage tank 21 Lower part of hot water storage tank

Claims (16)

  A fuel cell, a cooling water passage for circulating cooling water for cooling the fuel cell, a cooling water tank for storing the cooling water, and a cooling water supply for supplying the cooling water from the cooling water tank to the cooling water passage A fuel cell power generation system comprising a pipe and a cooling water switching valve that is attached to a path of the cooling water supply pipe and switches the cooling water to cold water having a temperature lower than that of the cooling water.   The fuel cell power generation system according to claim 1, wherein the cold water is supplied from tap water.   The fuel cell power generation system according to claim 1, further comprising cold water purification means for purifying the cold water.   2. The fuel cell according to claim 1, further comprising a flow rate control unit configured to control a flow rate of the cold water, wherein the flow rate control unit controls the flow rate of the cold water so that a difference between an inlet temperature and an outlet temperature of the cooling water flow path becomes small. Power generation system.   A heat exchanger for exchanging heat with the cooling water supplied to the fuel cell; a hot water storage tank for storing hot water heat exchanged by the heat exchanger; and a hot water storage pump for circulating hot water in the hot water storage tank, The fuel cell power generation system according to claim 1, wherein the pump is stopped while cold water is flowing through the cooling water flow path.   A heat exchanger for exchanging heat with the cooling water supplied to the fuel cell; a hot water storage tank for storing hot water exchanged by the heat exchanger; and a hot water tank switching valve disposed on the upstream side of the hot water storage tank. The hot water storage tank switching valve introduces hot water whose heat has been exchanged into the upper part of the hot water storage tank while the cooling water is flowing through the cooling water flow path, while the cold water is flowing through the cooling water flow path. 2. The fuel cell power generation system according to claim 1, wherein hot water flowing through the heat exchanger is switched to be introduced into a lower portion of the hot water storage tank.   Voltage detecting means for detecting the voltage of the fuel cell, and when the voltage detecting means detects that the voltage of the fuel cell exceeds a preset threshold value for a predetermined time or more, the cooling water flow path has a temperature lower than that of the cooling water. The fuel cell power generation system according to claim 1, wherein the cooling water switching valve is switched so that the cold water is supplied.   Voltage detection means for detecting the voltage of the fuel cell is provided, and the voltage detection means is the fuel cell while the fuel cell is generating power and the cold water having a temperature lower than the cooling water is supplied to the cooling water flow path. 2. The fuel cell power generation system according to claim 1, wherein the cooling water switching valve is switched so that the cooling water is supplied to the cooling water flow path when it is detected that the voltage of the first water exceeds a preset lower limit value.   A fuel cell, a cooling water passage for circulating cooling water for cooling the fuel cell, a cooling water tank for storing the cooling water, and a cooling water supply for supplying the cooling water from the cooling water tank to the cooling water passage A cooling water switching valve that is attached to a path of the cooling water supply pipe and that switches the cooling water to cold water lower in temperature than the cooling water, and a humidifying means that humidifies the fuel gas and the oxidant gas supplied to the fuel cell The cooling water switching valve is switched to condense the fuel gas and the oxidant gas humidified by the humidifying means with the cold water supplied to the cooling water flow path to generate condensed water, and the condensation A method for operating a fuel cell power generation system, wherein water is supplied to the fuel cell to restore the activity of the fuel cell.   Of the humidified fuel gas and oxidant gas, supply of at least the oxidant gas is stopped to stop power generation, and the cooling water switching valve is switched while lowering the voltage of the fuel cell to switch the cooling water flow 10. The fuel gas and the oxidant gas remaining in the cold water supplied to the passage are condensed to generate condensed water, and the condensed water is supplied to the fuel cell to restore the activity of the fuel cell. An operation method of the fuel cell power generation system described.   The fuel according to claim 9 or 10, wherein after the load is cut and the circuit is once opened, the supply of at least the oxidant gas of the humidified fuel gas and the oxidant gas is stopped to stop power generation. Operation method of battery power generation system.   The cooling water switching valve is switched to supply the cold water having a temperature lower than the cooling water to the cooling water flow path, the humidified fuel gas and the oxidant gas are supplied to start power generation, and the fuel gas and the After the oxidant gas is condensed to generate the condensed water, and the condensed water is supplied to the fuel cell to restore the activity of the fuel cell, the cooling water switching valve is switched to cool the cooling water flow path to the cooling water flow path. The operation method of the fuel cell power generation system according to claim 9, wherein water is supplied.   The cooling water switching valve is switched to supply the cooling water at a temperature lower than the cooling water to the cooling water flow path, and the humidified fuel gas and the oxidant gas are supplied. The operation method of the fuel cell power generation system according to claim 9 or 12, which starts.   Of the humidified fuel gas and oxidant gas, supply of at least the oxidant gas is stopped to stop power generation, and the cooling water switching valve is switched while lowering the voltage of the fuel cell to switch the cooling water flow The fuel gas and the oxidant gas remaining in the cold water supplied to the passage are condensed to generate the condensed water, the condensed water is supplied to the fuel cell, and the cold water is supplied to the cooling water passage. The humidified fuel gas and the oxidant gas are supplied to start power generation, the fuel gas and the oxidant gas are condensed to generate the condensed water, and the condensed water is supplied to the fuel cell. 14. After the activity of the fuel cell is recovered, the activation of the fuel cell is recovered by switching the cooling water switching valve and starting and stopping at least once to supply the cooling water. The method of operating a fuel cell power generation system according to any one.   When power is generated for the first time after installing the system, the cooling water switching valve is switched to supply the cooling water to the cooling water flow path, the fuel gas and the oxidant gas are condensed to generate the condensed water, The method of operating a fuel cell power generation system according to any one of claims 9 to 14, wherein start-stop is performed at least once to supply the condensed water to the fuel cell and restore the activity of the fuel cell.   After stopping the system for a long period of time, before generating electricity, switch the cooling water switching valve to supply the cooling water to the cooling water flow path, condense the fuel gas and the oxidant gas to generate the condensed water, The method of operating a fuel cell power generation system according to any one of claims 9 to 14, wherein start-stop is performed at least once to supply the condensed water to the fuel cell and restore the activity of the fuel cell.

Images